Volume V
A chest of miracles,
Close-packed and all secure, the unstable mass
Supported from a ruinous collapse
Or helpless flexion, by a spinous pile
Rigid as oak, yet flexile as the stem of the nodding flower.
Within, a nest of wonders, separate tasks
Each organ faithfully performing, still
From day to day harmoniously smooth
And uncomplaining, but for hindrances
Or ruinous urgence. Thou hast wisely said,
Melodious singer of old Israel,
"I am fearfully and wonderfully made."
E. C.
[Lesson I]
THE INTERRELATION
OF
FOOD CHEMISTRY AND PHYSIOLOGICAL
CHEMISTRY
FOOD CHEMISTRY AND PHYSIOLOGICAL CHEMISTRY UNITED
The human body is composed of fifteen well-defined chemical elements. A normal body weighing 150 pounds contains these elements in about the following proportions:
| POUNDS | OUNCES | GRAINS | |
|---|---|---|---|
| Oxygen | 97 | 12 | — |
| Carbon | 30 | — | — |
| Hydrogen | 14 | 10 | — |
| Nitrogen | 2 | 14 | — |
| Calcium | 2 | — | — |
| Phosphorus | 1 | 12 | 190 |
| Sulfur | — | 3 | 270 |
| Sodium | — | 2 | 196 |
| Chlorin | — | 2 | 250 |
| Fluorin | — | 2 | 215 |
| Potassium | — | — | 290 |
| Magnesium | — | — | 340 |
| Iron | — | — | 180 |
| Silicon | — | — | 116 |
| Manganese | — | — | 90 |
There are a number of other body-elements, but they are so remote that they have not been clearly defined by physiological chemists. All these body-elements are nourished separately, or, as it were, individually. They must be replenished in the body as rapidly as they are consumed by the vital processes, and this can be accomplished only through the action of the elements, in the forms of food, air, and water, received into the body and assimilated by it.
Where 91 per cent of human ills originate
From my professional experience I have estimated that about 91 per cent of all human ills have their origin in the stomach and the intestines, and are caused directly by incorrect habits in eating and drinking. If this is true, or even approximately true, it shows that, in its relation to health and the pursuit of happiness, food is the most important matter with which we have to deal; yet the average person devotes far less consideration to it than he does to the gossip of the neighborhood, or to the accumulating of a few surplus dollars.
Eminent writers agree as to importance of diet
Profs. Pavloff, Metchnikoff and Chittenden; Hon. R. Russell; Drs. Rabagliati, and Wiley, Ex-Chief of our Federal Bureau of Chemistry, and many other profound thinkers and writers have given in their various books an array of facts which prove beyond doubt that food is the controlling factor in life, strength, and health; yet they have given us but few practical suggestions as to how it should be selected, combined, and proportioned, so as to produce normal health, and especially how to make it remedial and curative, or to make it counteract the appalling increase in disease.
I have endeavored to begin where the great theorists left off—
1 By becoming familiar with the chemistry of food
2 By becoming familiar with the chemistry of the body
Food chemistry useless without body chemistry
Until my work began these two great sciences had been taught as distinct and separate branches of learning, while in reality physiological chemistry is but half of a science, and food chemistry is, in fact, the other half of the same science. The energy in food cannot be developed without the body—the body cannot develop energy without food. Each branch is worthless, therefore, without the other. In this work I have endeavored to unite them and to make of the two one practical, provable, and usable science.
RELATION OF SUPERACIDITY TO OTHER DISEASES
Nearly all stomach and intestinal troubles begin with superacidity. This is caused by the wrong combinations of food, or overeating. Food passing from the stomach, thus supercharged with Superacidity a primary cause acid, causes irritation of the mucous lining of the alimentary tract. This results in nervousness, insomnia, intestinal congestion (constipation), fermentation, and intestinal gas, while the excess of acid in the stomach causes irritation of the mucous surface of that much-abused organ, which develops first into catarrh, then ulceration, and sometimes into cancer. The accumulation of gas from the fermenting mass in the intestines causes irregular heart action, and sometimes heart failure. The great number of sudden deaths from this cause is pronounced by physicians "heart failure." In this the doctors and the writer agree—I know of no other way to die except for the heart to fail. The primary purpose of this work, however, is to ascertain why the heart fails, and, if possible, to remove the causes. From the fermenting food toxic (poisonous) substances, such as carbon dioxid, are generated, which, when taken into the circulation, become a most prolific source of autointoxication (self-poisoning).
From long experience gained by scientific feeding, in treating stomach and intestinal trouble, it became apparent that a great many disorders, very remote from the stomach, completely disappear when perfect digestion and assimilation of food, and thorough elimination of waste are effected. This has led to a very searching investigation of causes, and to the preparation of the following chart, which is designed to show how a great many so-called diseases can be traced back to one original cause—superacidity.
CHART, SHOWING THE NUMBER OF SO CALLED
DISEASES CAUSED BY SUPERACIDITY
Power to resist disease depends upon correct feeding
Aside from emotional storms, great nervous shocks, inoculation (vaccination), and violent exposure, nearly all diseases can be traced back to the stomach, or errors in eating. Even in cases of exposure, vaccination, or contagion, if the digestion and the assimilation of food, and the elimination of waste are perfect, the body will have the power to resist nearly all these causes of disease. Curing disease, therefore, by scientific feeding, is merely a method of removing causes and giving Nature a chance to restore normality.
Foods that ferment make inferior flesh
Food that sours, ferments, or that does not digest within Nature's time-limit, cannot make good bone and brain. A defective digestion that converts food into poisonous gases in the intestinal canal will make inferior flesh and blood, just as any other defective machine will turn out inferior work. This is the natural law governing all animal life.
Millions of learned people admit that good specimens of men and women can be constructed only out of good building material. They admit that the quality of a man, like that of a house, or a machine, depends upon the kind of material used in his construction; and yet Nature's protest against unsuitable building material they allow this important material to be selected and prepared by the most ignorant and unlearned, and they take it into their bodies with a childish thoughtlessness that is amazing; and when Nature imposes her penalty for violating her laws, they seek a remedy in drugs and medicines, and these are applied only to the symptoms which are merely the protest Nature is uttering. Thus a powerful drug silences or kills the friendly messenger who brought the timely warning, but the cause still remains. Suppose houses, ships, and machinery were constructed and repaired after this plan!
NATURAL LAWS DEMAND OBEDIENCE
Recompense for obedience to natural law, and punishment for its violation, are the invariable order of the universe, and are nowhere so effectively and emphatically demonstrated as in the cause and cure of the condition called disease.
There are certain laws which, if obeyed, will build the human body to its highest efficiency of energy, vitality and strength; but in order to obey these laws, one must know them, and in order to know them one must pass through the long and arduous mill of experience, or else learn from one who has done so.
Pain is a warning that something is wrong with the human mechanism, and he who tries to silence this signal with medicine will be punished for two wrongs instead of one. Nature tolerates no trifling, no deception; her laws are inexorable, her penalties inevitable.
Treating symptoms instead of causes
Multitudes of people are convinced that there is something wrong with their eating. Instead of food giving them the highest degree of mental and physical strength, which it should do, it actually produces ills and bodily disorders; moreover, not knowing the cause, people have no conception of a remedy other than drugs. It is amazing when one thinks how man, for two thousand years, has treated disease. Instead of studying causes and endeavoring to remove them, he has treated symptoms and symptoms only. It is generally known that the practise of medicine consists in treating symptoms rather than causes. For example, nearly all headaches—one of our common afflictions—are caused indirectly by impaired digestion, faulty secretion and excretion, yet the drug stores and Materia Medica (the Bible of the profession), are laden with "headache cures," all of which act only upon the symptoms. The whole system of drugging people when they are sick is merely a method of quieting the signals—of killing or paralyzing the messengers. Most drugs, taken into the human body, are merely diminutive explosives, the effect of which is destructive. They are like a lash cruelly applied to a willing servant who lags from sheer exhaustion.
"Ease" and "Dis-ease"
Since symptoms are really the language of Nature, if we learn to interpret them, we need never err in diagnosis, and consequently never err in getting directly at the causes, as we must do in order to "cure." A drug that could cure a disorder caused by wrong feeding would perform a miracle. It would reverse one of the fixed laws of the universe. It would produce an effect without a cause. Nature works along the lines of least resistance, and points out with unerring certainty the best, the cheapest, and the easiest way to live. Health was originally called "ease." People who did not have health were in disgrace or "dis-eased."
HOW TO MAKE HUMAN NUTRITION A SCIENCE
Human nutrition cannot be made a science under the conventional methods of omnivorous eating—eating anything and everything without thought or reason. Nutrition can only be made a science by limiting the articles of food to such things as will reproduce all the chemical elements of the human body, mentioned at the beginning of this lesson.
The further we remove foods from their natural state, the more difficult becomes their analysis, their reliability, and a knowledge of their chemistry, therefore the menus that appear in this work include only the foods that will give to the body the best elements of nutrition.
Prepared foods unscientific
There is but little difficulty in ascertaining the chemistry of natural foods, but when they have been preserved, pickled, canned, smoked, evaporated, milled, roasted, toasted, oiled, boiled, baked, mixed, flavored, sweetened, salted, soured and put into the popular commercial forms, it becomes very difficult, if not impossible, to know what we are eating, or to estimate the results.
Man is the net product of what he eats and drinks. Food bears very much the same relation to him that soil does to vegetation. The following questions, therefore, should be solved by every one who believes that success and happiness depend upon health and vitality:
1 How to select and how to combine foods which will give to the body a natural result, which is health
2 How to select and how to combine foods so that they will counteract and remove the causes of dis-ease
3 How to select foods which contain all the chemical elements of the body, and how to combine and proportion them at each meal so that they will chemically harmonize
4 How to determine the quantity of food to be taken each day, or at each meal, that will give to the body all the nourishment it is capable of assimilating
Note: Too much food, even of the right kind, defeats this purpose and produces just the opposite result.
Upon this knowledge hinges the building of a natural body, the cure of a vast majority of dis-eases, our ability to reach the highest state of physical and mental vitality, the prolongation of youth and longevity.
OUR FOOD MUST FIT INTO OUR CIVILIZATION
We must make our diet fit into our civilized requirements. Civilization has imposed many customs, habits, and duties upon us that have not been properly met by nutrition or diet. This is why nearly 91 per cent of our ills are caused by errors in eating.
Effect of sedative occupations upon nutrition
Under continued physical exertion, the body will thrive for a time on an unbalanced diet. It will cast off surplus nutrition, and convert one element into another, a problem unknown to modern science, but under sedative or modern business habits and occupations, it will not continue to cast off a surplus, or to reconvert nutritive elements. As a result of an unbalanced bill of fare, the nutrients taken in excess of the daily needs undergo a form of decomposition, producing what is called autointoxication, and become a most prolific source of dis-ease.
WHY THE SCIENCE OF HUMAN NUTRITION IS IN ITS INFANCY
The reader may inquire why it is that all other branches of science have advanced so rapidly, and the science of human nutrition has just begun. The reasons are:
1 Our ancestors, for many thousand years, were taught that dis-ease was a visitation of Divine Providence, therefore to combat it was to tempt the Almighty.
2 Doctors of medicine who have been custodians of the people's health for many centuries have seldom been food scientists. Most of them attempt to combat disease with drugs.
Now we are beginning to learn the truth about the origin of disease and in considering the body as a human engine, to take into consideration the all-important question of fuel.
Tendency of the modern physician toward food science
That the most learned physicians are drifting more and more toward scientific feeding and natural remedies is a matter of common knowledge. This splendid army of laborers in the great field of human suffering is made up largely of what is termed the Modern Doctor—the man who is brave enough to think and to act according to his better judgment.
Just to the extent that we understand the origin of drugs, and the drugging system of treating dis-ease, we turn instinctively from them, and instinctively toward food, for in drugs we find an ancient system of guesswork, while in food we find fundamental principles and primary causes. The majority of causes are removed when the diet is made to fit our physical condition and environment, and we then become normal by the process of animal evolution, Nature merely bestowing upon us our birthright because we have obeyed her laws.
3 The true science of human nutrition can be evolved only from an accurate knowledge of both food chemistry and of physiological chemistry.
Why food chemistry and physiological chemistry have not been united
The science of physiological chemistry has been known and taught for more than one hundred years, while the science of food chemistry is of recent origin. These two branches have been kept separate because they grew up at different periods of time. United they constitute the greatest science known to mankind, because they affect his health, his happiness, his life, and above all they measure the period of time he will live.
Physiological chemistry tells what the body is and its needs—food chemistry tells how to supply these needs. Recognizing these facts, I have merely united these hitherto unapplied branches of science, and have made of the union the science of Applied Food Chemistry, which makes practical that which has heretofore been confined mainly to theory.
[LESSON II]
SIMPLE PRINCIPLES OF GENERAL CHEMISTRY
Relation of chemistry to food science
If the student is versed in chemistry, this lesson will serve merely as a review; if not, somewhat close attention must be given to facts which at first may seem uninteresting. Patience should be exercised, for, while all the information herein given does not, taken as a whole, bear directly upon the subjects of health and dis-ease, yet with this knowledge it will be much less difficult to understand the principles which are applied later when we take up the chemistry of the body and the chemistry of food.
Chemistry is not, as popularly supposed, a science far removed from everyday life. Everyone has some knowledge of chemistry, but the chemist has observed things more minutely and therefore more accurately understands the composition of substances and the changes that are everywhere taking place. For illustration:
A cook starts a fire in a stove. She knows that the fire must have "air" or it will not burn; that when the fire is first lighted, it "smokes" heavily, but as it burns more, it smokes less; further, that if the damper in the pipe is closed the "gas" will escape in to the room.
Fire, gas, and smoke the result of chemical changes
The chemist also knows this, but because he has compared his observations with similar events elsewhere, he is enabled to express his knowledge in the language of science. To the chemist, fire is the process of combustion—the union of the oxygen of the air with the carbon and hydrogen compounds of the wood or of the coal. The heat of the fire is generated by this chemical union. To the chemist, the smoke is a natural phenomenon occasioned by particles of carbon which fail to unite with the oxygen gas. The gas, which to the woman suggests suffocation if enough of it escapes into the room, to the chemist suggests a compound resulting from combination of the oxygen with the carbon.
CHEMICAL ELEMENTS
To the chemist, all forms of matter are mere combinations of elements. Chemical analysis is a process of separating, dividing, and subdividing matter. When the chemist separates or analyzes compounds, until he can no longer simplify or subdivide them, he calls these simple products "chemical elements."
Common elements
Many of the chemical elements are well known, such as copper, iron, and gold. Other elements that are still more common are unknown in their elementary form, because they combine with other elements so readily that they exist in nature only as compounds. For example: Hydrogen, united with oxygen, forms water; the elements chlorin and sodium, combined or united, form common salt.
Number of elements
Altogether chemists have discovered about eighty-four elements, many of which are rare, and do not occur in common substances.
All substances of the earth, whether dead or living, are formed of chemical elements. These elements may be found in the pure or elementary state, or they may be mixed with other substances, or they may be combined chemically. Copper, iron, and gold are elements in the pure state. If we should take iron and copper filings and mix them together, we would still have copper and iron. Were we to take copper and gold and melt them together, we would have a metal that would be neither copper nor gold. It would be harder than one and softer than the other. But this substance would still be a mixture, and its properties half way between copper and gold.
Examples of chemical changes
If a piece of iron be exposed to dampness it will soon become covered with a reddish powder called "rust." The rusting of iron is a process of chemical changes in which the original substance was wholly changed by chemically uniting with the oxygen and the moisture of the atmosphere, which is really a process of combustion. The burning of wood, the rusting of iron, the souring of milk, and the digestion of food are, in a way, all mere examples of chemical changes.
Difference between chemical compounds and simple mixtures
Care should be exercised to distinguish chemical compounds from simple mixtures. Air is not a compound, but a mixture of oxygen, hydrogen and nitrogen gases. Water, however, is a compound of oxygen and hydrogen. Both salt and sugar are compounds, but if we grind them together, we do not have a new compound, but a mixture of two compounds. Most of the common things around us are mixtures of different compounds or substances. Rocks are mixtures of many different compounds. Wood is, likewise, formed of many different substances. Wheat contains water, starch, cellulose, and many other compounds. Grinding the wheat into flour does not change it chemically, but if we heat the flour in an oven, some of the starch is changed into dextrin. The starch has disappeared, and dextrin, a new substance, appears in its place. Whenever elements are combined into compounds, or compounds broken up into elements, or changed into other compounds, we have true chemical action.
The names of the elements are formed in many different ways. The name chlorin is derived from a Greek word meaning greenish-yellow, as this is the color of chlorin. Bromin comes from a Greek word meaning a stench, a prominent characteristic of bromin being its bad odor. Names of elements—how derived Hydrogen is formed from two Greek words, one of which means water and the other to produce, signifying that it enters into the composition of water. Potassium is an element found in potash, and sodium in soda, etc.
Symbols of elements—how derived
For convenience, abbreviations are used for the names of elements and compounds. Thus, instead of oxygen, we may write simply "O"; for hydrogen, "H"; for nitrogen, "N," etc. Very frequently the first letter of the name of the element is used as the symbol. If the names of two or more elements begin with the same letter, some other letter of the name is added. In some cases the symbols are derived from the Latin names of the elements. Thus, the symbol of iron is Fe, from ferrum; of copper, Cu, from cuprum.
The following table gives the names of the elements which it will be necessary to understand in pursuing this work.
| Aluminum | Al | Gold | Au; | Phosphorus | P |
| Arsenic | As | Hydrogen | H | Platinum | Pt |
| Boron | B | Iodin | I | Potassium | K |
| Bromin | Br | Iron | Fe | Silicon | Si |
| Calcium | Ca | Lead | Pb | Silver | Ag |
| Carbon | C | Magnesium | Mg | Sodium | Na |
| Chlorin | Cl | Mercury | Hg | Sulfur | S |
| Chromium | Cr | Nickel | Ni | Tin | Sn |
| Copper | Cu | Nitrogen | N | Zinc | Zn |
| Fluorin | F | Oxygen | O |
AIR AND OXYGEN
Composition of air
Air—The air consists chiefly of two substances, only one of which can keep up the process of burning. This substance is known as oxygen. The other, in which nothing can burn, is known as nitrogen. Besides these the air contains smaller quantities of other substances, particularly water vapor, carbonic acid (carbon dioxid), ammonia, and carburetted hydrogen.
Distribution of oxygen
Oxygen—Oxygen is the most common element in nature. It forms between forty and fifty per cent of the solid crust of the earth, eight-ninths of all the water on the globe, and one-fifth of all the air around the globe.
We have oxygen around us in great abundance, but it is mixed with nitrogen, and it is difficult to separate the two so as to secure the oxygen for any practical or commercial use.
MANUFACTURE OF OXYGEN
There are three methods of obtaining oxygen:
1 From potassium chlorate, or, as it is commonly called, chlorate of potash.
When potassium chlorate (KCLO3) is heated in a closed vessel (closed vessel means "closed at one end"), it breaks up into potassium chlorid and oxygen; that is, KCLO3 + heat = KCL + O3.
Potassium chlorate is used in fireworks because it gives up its oxygen readily. Potassium nitrate serves the same purpose in gunpowder, which is a mixture of sulfur (S), charcoal (C), and salt-peter or potassium nitrate (KNO3). The explosion of gunpowder, after a certain temperature has been reached, is due to the formation of oxygen, which, combined with the potassium nitrate, is set free by the very rapid burning of the charcoal and the sulfur. Other gases formed by the explosion are nitrogen, and probably sulfur dioxid (SO2), and oxids of nitrogen, N2O, NO2, etc. Carbon monoxid and carbon dioxid are sometimes formed. Potassium nitrate, however, is the most active agent in gunpowder.
2 By the electrolysis of water.
By this method the oxygen and the hydrogen are separated by electricity.
3 By the liquefaction of air, which is a very recent and a very scientific method.
By this method the air is cooled down until it liquefies. At normal atmospheric pressure it liquefies at a temperature of —312.6°F., but under pressure of about 585 pounds it liquefies at a temperature of —220°F. After the air has been liquefied, it is allowed to go back to vapor by exposing it to the surrounding heat of the atmosphere, and this vaporization separates the nitrogen from the oxygen, as the nitrogen boils at a temperature of —318°F., while the oxygen boils at a temperature of —294°F. There is a difference of about 24° in the boiling points of these two gases, which at this low point amounts to more than the difference between the boiling points of alcohol and water, and this difference is sufficient to separate the oxygen from the nitrogen.
Production of oxygen by the liquefaction of air is the latest, cheapest, and most approved method, and is now becoming extensively used in obtaining both oxygen and nitrogen for commercial use.
Properties of oxygen
Oxygen is tasteless and odorless. It is slightly heavier than air. When subjected to an extremely high pressure and low temperature it becomes liquid.
CHEMICAL ACTION OF OXYGEN
(a) Upon Substances
Effect of air upon iron and wood
Upon some substances oxygen acts at ordinary temperature. Iron becomes covered with rust when exposed to air and moisture. Wood and other vegetable and animal substances undergo slow decomposition when exposed to the air. This is partly due to the action of oxygen at ordinary temperature.
Pure oxygen aids combustion
A splinter of wood will burn brilliantly in a jar of pure oxygen, and much more rapidly than in common air. Pure oxygen gas will cause many substances to burn which will not burn in air. Iron can be burned in pure oxygen, leaving only a reddish powder.
Formation of iron-rust
When iron rusts the carbon dioxid and water vapor combine chemically with the iron, and form what is known as a basic hydroxid or carbonate of iron. The process is somewhat complex. When iron burns in oxygen a red powder is formed—ferric oxid, Fe2O3. Iron dissolves in water, or moisture from the air containing carbonic acid, forming acid ferrous carbonate—
Fe + 2H2CO3 = FeH2(CO3)2 + H2
Iron + Carbonic acid = Acid ferrous carbonate + Hydrogen
This acid ferrous carbonate, on drying or further oxidation, is converted into iron-rust. If we represent iron-rust by the formula Fe2O3. 2Fe(OH)3, the equation is as follows:
4FeH2(CO3)2 + O2 = Fe2O3. 2Fe(OH)3 + H2O + 8CO2
Acid ferrous carbonate + Oxygen = Iron-rust + Water + Carbon dioxid
(b) In Living Bodies
The most interesting action of oxygen at ordinary temperature, however, is that which takes place in our bodies and the bodies of all other animals.
By the constant action or beating of the heart all the blood in the body is brought to the lungs every two or three minutes. The actual time has not been determined in man. In large arteries the Rate of blood circulation blood flows ten times as fast as in very small ones. The usual time through a capillary is one second. The time has been determined, however, in lower animals. In a horse the blood travels one foot a second in the largest artery. At present the accepted theory is that in the circuit the blood makes throughout the body, it picks up the waste matter Oxidation of waste matter from tissue that has been torn down by work or effort, and brings it to the lungs, where it meets with the oxygen we breathe and is oxidized or burned.
If the body undergoes excessive effort or exercise, it tears down an excessive amount of tissue, and there is created, therefore, an excessive amount of waste or carbon dioxid. Nature very wisely provides for this contingency by increasing the heart action, thereby sending the blood through the body at greater velocity, forcing more blood to the lungs, thus increasing the demand for oxygen, which is expressed by deep and rapid breathing.
Generation of heat and light
When a substance burns it gives off heat, and generally light. The heat is the result of chemical change or combination, and the light is the result of heat. Whenever oxidation takes place, no matter in what form, heat is produced.
Amount of heat determined by amount of oxygen
The amount of heat given off by the combination of a given amount of oxygen with some other substance is always the same. If it takes place at a very high temperature, as in explosives, the heat is all given off at once, but if it takes place more slowly, the heat passes away, and we may not observe it, but careful experiments prove that heat is always present in oxidation, and the amount of heat is always measured by the amount of oxygen.
Law governing oxidation of given quantity of food
That the combination of oxygen with other substances always produces a certain amount of heat is a very important fact to the food scientist, as this law enables him to determine in the laboratory the exact amount of heat that is produced in the oxidation of a pound, or of any given quantity of food; this food will also produce exactly the same amount of heat if oxidized in the human body.
Heat and motion
We know that by means of heat we can produce motion. The steam-engine is the best example of this law. We build a fire under the boiler; the oxygen of the air unites with the carbon in the coal; the combustion converts the water into steam; the steam is conveyed to a cylinder; the pressure pushes a piston; the motion of the piston causes motion in the engine, and the train or ship moves.
Determination of body-heat and energy
From such facts we know that not only the amount of heat, but the amount of work or energy that food or fuel will yield can be determined with reasonable accuracy. Many conditions obtain in the body, however, that do not occur in the laboratory, hence we must study these conditions before we can fully understand the natural laws that govern the production of heat, and energy or work, by oxidation in the living body.
HYDROGEN AND WATER
Distribution and production of hydrogen
Hydrogen—Hydrogen is found in nature very widely distributed and in large quantities. It forms one-ninth of the weight of water, and is contained in all the principal substances which enter into the composition of plants and animals. It may be obtained by decomposition of water by means of the electric current, or by the action of substances known as acids on metals. The latter method is more commonly used in the laboratory. Acids contain hydrogen, give it off easily, and take up other elements in its place. Among the common acids found in every laboratory are hydrochloric, sulfuric, and nitric.
Physical properties of hydrogen
Pure hydrogen is a colorless, odorless, tasteless gas. It is not poisonous, and may therefore be inhaled without harm. It is the lightest known substance, being about 14.4 times lighter than air, 16 times lighter than oxygen, and 11,000 times lighter than water.
Chemical properties of hydrogen
Hydrogen does not unite with oxygen at ordinary temperatures, but, like wood and most other fuel substances, needs to be heated up to the kindling temperature before it will burn. Hydrogen burns if a lighted match be applied to it. The flame is colorless, or very slightly blue.
Decomposition of water
Water—Water is a compound and not an element, as can be shown by passing an electric current through it. If the ends of two wires, each connected with an electric battery, be put a short distance apart, in acidulated water, it will be noticed that bubbles of gas rise from each wire. As these gases cannot come from, or through the wires, they must be formed from the water. If they be analyzed, we will find that oxygen gas comes from one wire and hydrogen from the other.
Proportion of hydrogen and oxygen in water
This experiment shows that when an electric current is passed through water, hydrogen and oxygen are obtained, and also that there is obtained twice as much hydrogen as oxygen by volume. This proves that water is not an element, but a compound of two atoms of hydrogen and one of oxygen. The chemist therefore writes the symbol for water H2O.
We have just learned that with electricity we could decompose the compound water into its elements, hydrogen and oxygen. Now we can prove by another experiment that water contains these two elements. If we burn hydrogen gas, or any substance containing hydrogen, water is formed. This can be illustrated by inverting a cool, dry tumbler over a gas flame, which is composed chiefly of hydrogen, and water vapor will collect on the inside.
Properties of water
Though water is widely distributed over the earth, we never find it absolutely pure in nature. All natural waters contain foreign substances in solution. These substances are taken up from the air, or from the earth. Pure water is colorless, tasteless, and odorless.
Why ice floats
On cooling, water contracts until it reaches the temperature of 4° Centigrade (39° Fahrenheit). When cooled from 4° to 0° C. it expands, and the specific gravity, or weight compared with the space occupied by ice, is somewhat less than that of water; hence ice floats.
Rain-water
Mineral water
The purest water found in nature is rain-water, particularly that which falls after it has rained for some time; that which first falls always contains impurities from the air. As soon as rain-water comes in contact with the earth and begins its course toward the sea, it also begins to take up various substances according to the character of the soil with which it comes in contact. Mountain streams which flow over rocky beds, particularly beds of sandstone, contain very pure water. Hard water Streams which flow over limestone dissolve some of the stone, and the water becomes "hard." The many varieties of mineral water from the various springs throughout the country, take their properties from soluble substances with which they come in contact.
Salt water
Common salt is deposited in large quantities in different parts of the earth. Since salt is readily soluble in water, many streams pick up large quantities of it, and as all water courses ultimately find their way to the ocean, the latter becomes a repository for salt with which the earth-water is laden.
Effervescent waters
Effervescent waters all contain some gas, usually carbonic acid gas in solution, and they merely give up or set free a part of it when placed in open vessels.
Sulfur water
Sulfur water contains a compound of hydrogen and sulfur, called hydrogen sulfid or sulfureted hydrogen, which we will refer to in its order later in this lesson.
Distilled water
Water may be purified by means of distillation. This consists in boiling the water and condensing the vapor by passing it through a tube which is kept cool by surrounding it with cold water. By means of distillation most substances in solution in water can be eliminated. Substances, however, which evaporate like water, will, of course, pass off with the water vapor. Aboard ship salt water is distilled and thus made fit for drinking. In chemical laboratories ordinary water is distilled in order to purify it for chemical work.
USES OF WATER IN CHEMISTRY
Action of water in physiological chemistry
Water is termed by the chemist a stable compound. This means that it is difficult to get it to act chemically. Being thus inactive chemically, we find that water does not combine with most substances. There are exceptions to this, however, especially in physiological chemistry, an instance being that starch combines with water when it is changed to sugar in the process of digestion.
Water as a solvent
Water is the universal solvent. A greater number of substances dissolve in it than in any other liquid. Chemical operations are frequently carried on in solution, that is to say, the substances which are to act chemically upon each other are first dissolved in water. The object of this is to get the substances into as close contact as possible. If we rub two solids together, the particles remain slightly separated, no matter how finely the mixture may be powdered. If, however, the substances are dissolved and the solutions poured together, the particles of the liquid move so freely among each other that they come in direct contact, thus aiding chemical action. In some cases substances which do not act on each other at all when brought together in dry condition, act readily when brought together in solution.
There is a limit to the amount of any substance which can be held in solution at a given temperature.
Chemical meaning of solution
The question will probably arise in the mind of the student as to whether a substance dissolved in water has chemically united with the water, or is merely mixed. Solution is in reality a process about half way between mixing dry substances and forming chemical combinations. The chemist considers that the water does not form a compound with the substance dissolved, when he can, by evaporating the water, get the substance back into its original form.
IMPORTANCE OF SOLUTION TO THE FOOD SCIENTIST
Solution is very important in the study of foods and human nutrition. Only substances which can be dissolved can be assimilated. Many substances which Relation of solution to assimilation will not dissolve in pure water will dissolve in water which contains something else in solution. The blood is water containing many things in solution. The salts of the blood keep the other food elements in solution, many of which would not dissolve if the blood did not contain these salts. The chief work of the digestive juices is to reduce foods to a soluble form so that they can be taken into the circulation by absorption; otherwise they would pass through the alimentary canal practically unchanged.
Milk as an example of both "Solution" and "Mixture"
We must learn to distinguish carefully between chemical solution and merely mixing things with water. A good example is milk. In addition to water, milk contains principally fat, sugar, and casein. The sugar is truly dissolved in the water. The fat and the casein are fine particles held in suspension. If the milk stands for a while, the fat particles rise to the top as cream. If it stands long enough, the casein particles adhere to each other and settle to the bottom, leaving the water with the dissolved sugar or whey in the middle.
IMPORTANCE OF WATER IN THE HUMAN BODY
Proportion of water and solids in the human body
Water, which forms about sixty-six per cent of the human body, is by far the most important substance therein. It comprises the major part of the blood serum and every tissue and organ. If a normal human body weighing 150 pounds were put into an oven and thoroughly dried, there would be left only about 50 pounds of solid matter, all the rest being water. The proportion of water in animal and vegetable substances is also very great. As water is also a conspicuous factor in all foods, either in chemical combination, or in solution with other elements mechanically mixed, it is obvious that water is an important factor in food science.
USES OF WATER IN THE BODY
The uses of water in the body may be roughly grouped into three divisions, as follows:
1 Water in small quantities enters into the actual chemical composition of the body.
As we will notice in the discussion of carbohydrates, water combines chemically with cane-sugar when it is digested and transformed into glucose. (See Lesson IV, "Cane-sugar," page [112.])
2 Water forms a portion of the tissues and acts as a solvent in the body-fluids.
What blood carries in solution
In this function the water is not changed chemically, but is only mixed with other substances; thus the blood is in reality water with glucose, peptone, etc., in solution, and carrying along with them red blood-corpuscles and fatty globules.
3 Water is a most important factor in the digestion, and the assimilation of food, and the elimination of waste.
Drinking with meals
Inasmuch as the body is nearly two-thirds water, it follows that the diet should be composed of about 66 per cent moisture. The old theory of dietitians that no water should be taken with meals was based upon the hypothesis that the water diluted the gastric juice, and that this diluted form of the gastric juice weakened its digestive power. Actual practise has proved this thesis to be untrue. Water is the great universal solvent, and the hydrochloric acid of the stomach is only a helper, as it were, in the dissolution or the preparation of food for digestion.
Water is also a valuable agent in the elimination of body-poisons.
Value of water to blood
The liberal use of water keeps the blood supplied with the necessary moisture, and that excess which is eliminated through the kidneys carries away poisons that would reside in the body very much to the detriment of health. There is little danger, therefore, in drinking too much pure water, but much care should be exercised that it be pure, or at least free from lime and mineral deposits. The best water is pure water, free from all mineral substances.
If a meal consists of watery food, such as fresh vegetables, salads, etc., then the drinking of water becomes unnecessary; but When water drinking is unnecessary where the meal is composed chiefly of solids, then an amount of water should be taken sufficient to make up 66 per cent of the total. If more water is taken than is necessary for this purpose, the excess will pass off and the stomach will only retain the necessary amount; but if the quantity of moisture is insufficient, the stomach calls to its aid an excess of hydrochloric acid, the strength of which has a tendency to crystallize the starch atom (especially cereal starch), thereby causing the blood-crystal, which is one of the primary causes of rheumatism, gout, Disorders caused by insufficient moisture lumbago, arterial sclerosis (hardening of the arteries), and all disorders caused by congestion throughout the capillary and the arterial systems. The most common disorder among civilized people is hydrochloric acid fermentation. Copious water drinking at meals is the logical remedy for this disorder.
The proper amount of pure non-mineral water taken with food will do much to remove the causes of superacidity and the long train of ills that follow this disorder. (See "Chart," Lesson I, page [9.])
In this work I shall constantly refer to these various uses of water, especially as a solvent (an aid to digestion), and as a remedial and curative agent.
Man's source of water
Theories have been promulgated by hygienic teachers in the past few years that man should get his supply of water wholly from the juices of fruits, and not drink ground-waters, which are contaminated with mineral substances. While it may be true that water in certain localities, such as in the alkali deserts, is unfit for drinking, yet the writer believes that the promulgators of the theory that man is not a drinking animal never did a hard day's work in a harvest field. In the dry winds of the western plains water evaporates from the surface of the body at the rate of twelve or fifteen pounds a day. The theory of deriving one's water supply wholly from fruits would not stand the test of such facts.
NITROGEN AND NITROGEN COMPOUNDS
Sources of nitrogen
We have learned that the air is composed chiefly of oxygen and nitrogen. These are not combined as oxygen and hydrogen are in water, but are simply mixed together, four-fifths of the mixture being nitrogen. Nitrogen is also found in combination in a large number of substances in nature. It is found in the nitrates, as salt-peter or potassium nitrate, KNO3, and Chili salt-peter or sodium nitrate, NaNO3. It is also found in the form of ammonia, which is a compound of nitrogen and hydrogen of the formula NH3, and exists in that form in a limited quantity of the air. In most foods, especially in those of animal origin, nitrogen occurs in chemical combination.
Properties of nitrogen
Nitrogen is a colorless, tasteless, odorless gas which does not burn, and does not combine readily with oxygen, or with any other element except at a very high temperature, and except in the formation of living plants, or in animal life. Just as nitrogen does not support combustion, so also it does not support life. An animal would die confined in a tank of nitrogen, not on account of any active poisonous properties in the nitrogen, but for lack of oxygen.
Compounds of nitrogen
When a compound containing carbon, hydrogen and nitrogen is heated in a closed vessel, so that the air is excluded, and so that it cannot burn, the nitrogen passes out of the compound, not as nitrogen, but in combination with hydrogen, which forms ammonia. Nearly all animal substances contain carbon, hydrogen, oxygen, and nitrogen, and many of them give off ammonia when heated as above described.
Why ammonia is used in making artificial ice
Ammonia is written by the chemist NH3, or one part of nitrogen gas to three parts of hydrogen. It is a colorless, transparent gas with a very penetrating, characteristic odor. In concentrated form it causes suffocation. It is but little more than half as heavy as air. It is easily converted into liquid form by pressure and cold. When pressure is removed from the liquefied ammonia, it passes back very rapidly into gaseous form, and in so doing it absorbs heat. Investigators have taken advantage of these facts and are employing liquid ammonia in the manufacture of artificial ice.
While air is merely a mixture of oxygen and nitrogen, this does not prove that these two elements cannot unite. In fact they do unite in five different proportions so as to form five different substances. These are given below to illustrate how different substances can be formed from Importance of proportioning food the same things, by merely combining them in different proportions. This example is also given to impress upon the mind of the practitioner the great importance of proportioning nutritive elements in diet so that the patient will not be overfed on some elements while underfed on others. It is absolutely essential, in order to know what effect a substance will have in the laboratory, or in the body, to know not only of what it is composed, but with what substances and in what proportions it is combined.
| Nitrous oxid | N2O |
| Nitric oxid | NO or N2O2 |
| Nitrogen trioxid | N2O3 |
| Nitrogen peroxid | NO2 or N2O4 |
| Nitrogen pentoxid | N2O5 |
To further illustrate the wonders of chemical combinations, we give the properties of two of these oxygen and nitrogen compounds:
Properties and uses of nitrous oxid
Nitrous oxid, N2O, is colorless, transparent, and has a slightly sweetish taste. When inhaled it causes a kind of intoxication which manifests itself in the form of hysterical laughing, hence it is commonly called "laughing gas." Inhaled in larger quantities it causes unconsciousness and insensibility to pain. It is, therefore, used in many surgical operations, particularly by dentists in extracting teeth.
Nitrogen peroxid, NO2, is a reddish-brown gas. It has an extremely disagreeable odor and is very poisonous.
Composition of nitric acid
By oxidation the nitrogen of animal substances is converted into nitric acid, HNO3. Furthermore, the silent, continuous action of minute living organisms in the cell is always tending to transform the waste-products of animal life into compounds closely related to nitric acid. This acid, as its chemical formula indicates, is formed by the combination of the three elements we have just studied, namely, hydrogen, nitrogen, and oxygen. Pure nitric acid is a colorless liquid. It gives off colorless, irritating fumes, when exposed to the air. Strong nitric acid acts violently upon many substances, particularly those of animal and Properties of nitric acid vegetable origin, decomposing them very rapidly. Nitric acid burns the flesh, eats through clothing, disintegrates wood, and dissolves metals. It is one of the most active of chemical substances.
The compounds of nitrogen that occur in food are very numerous and of complex composition. They will be discussed in Lessons III and IV, pages [99] and [125] respectively.
CHLORIN
Sources of chlorin
Chlorin, though widely distributed in nature, does not occur in very large quantities as compared with oxygen and hydrogen. It is found chiefly in combination with the element sodium, as common salt or sodium chlorid, which is represented by the symbol NaCl.
Properties of chlorin
Chlorin is a greenish-yellow gas. It has a disagreeable smell and acts upon the passages of the throat and nose, causing irritation and inflammation. The feeling produced is much like that of a cold in the head. Inhaled in concentrated form, that is, not diluted with a great deal of air, it would cause death. It is much heavier than air, combines readily with other substances, and possesses the property of bleaching or destroying colors.
HYDROCHLORIC ACID
Just as hydrogen burns in the air, so it burns in chlorin. The burning of hydrogen in air or oxygen is, as we have seen, simply the combination of hydrogen and oxygen, the product being water in the form of vapor, and therefore invisible. Hydrogen and chlorin combined When hydrogen burns in chlorin, the action consists in the union of the two gases, the product being hydrochloric acid, HCl, which forms clouds in the air. The two gases, hydrogen and chlorin, may be mixed together and allowed to stand together indefinitely in the dark, and no action will take place. If, however, the mixture be put into a room lighted by the sun, but where the sun does not shine directly upon it, combination takes place gradually; but if the sun be allowed to shine directly upon the mixture for an instant, explosion occurs, this being the result of the combination of the two gases. The same result can be caused by applying a flame or spark to the mixture. In this case light causes chemical action. The art of photography depends upon the fact that light has the power to cause chemical changes.
Importance and preparation of hydrochloric acid
I will here consider hydrochloric acid somewhat in detail, because it is very important in the digestion of food, being the principal fluid composing the gastric juice of the stomach. Hydrochloric acid is always made by treating common salt (one afflicted with acid fermentation should omit the use of salt and soda), under high temperature, with sulfuric acid. This product is given off as a gas, which dissolved in water forms hydrochloric acid, sodium sulfate remaining behind as a result of this process. The chemist describes the action that takes place by writing what is called a chemical equation, as follows:
2NaCl + H2SO4 = Na2SO4 + 2HCl
Sodium chlorid + Sulphuric acid = Sodium + Hydrochloric acid
(common salt) Sulfate
The reader will observe that there are as many parts of each element on the right as on the left-hand side of the = mark. Two parts of common salt yield two parts each of sodium (Na) and chlorin (Cl). The sodium appears as Na in the sodium sulfate, and the chlorin as Cl in the two parts of hydrochloric acid.
This method of expressing chemical action by these equations may be somewhat confusing at first to those who have not studied chemistry, but it is best to have all such become familiar with them that they may have the further benefit of understanding the general terms of chemistry.
Hydrochloric acid gives up its hydrogen when brought into contact with certain metals like iron, zinc, etc., and takes up these metallic elements in place of the hydrogen. Thus zinc and hydrochloric acid give zinc chlorid and hydrogen.
Zn + 2HCL = ZnCl2 + H2
Zinc + Hydrochloric acid = Zinc chlorid + Hydrogen
ACIDS, BASES, NEUTRALIZATION, SALTS
We have already discussed a number of substances called acids. It is necessary to inquire why chemists call them acids. What is there in common, for example, Relation of acids to bases between the heavy, oily liquid sulfuric acid and the colorless gas, hydrochloric acid? It is not possible to understand the nature of their common properties without examining a class of substances called alkalis or bases.
Acids and bases have the power to destroy the characteristic properties of each other. When an acid is brought into contact with a base, in proper proportions, the characteristic properties of both the acid and the base are destroyed. They are said to neutralize each other.
The most common acids are sulfuric, hydrochloric, and nitric. Among the more common bases are caustic soda, caustic potash, and lime. A convenient way to recognize whether a substance has acid or basic properties is by means of certain Common acids and bases and tests therefor color-changes. Litmus is a coloring matter which is ordinarily blue. If a solution which is colored blue with litmus be treated with a drop or two of an acid, the color is changed to red. If the red solution be treated with a few drops of a solution of a base, the blue color is restored.
Many substances change in color according to whether the solutions in which they are present are acid or alkaline. An infusion of red cabbage, for example, changes color when treated with an acid, and recovers its color when again treated with an alkali.
Formation of common salt
What happens in the chemical sense in this neutralizing process is nicely illustrated by the formation of common salt from hydrochloric acid and caustic soda, also called sodium hydroxid. When these two substances are dissolved in water, and the solutions mixed, the chemical action is as follows:
HCL + NaOH = H2O + NaCl
Hydrochloric acid + Caustic soda = Water + Common salt
(Muriatic acid) (Sodium hydroxid) (Sodium chloride)
The strong hydrochloric acid with its pungent odor and sour taste, and the caustic alkali with its equally characteristic properties have both disappeared, Common examples of neutralization and in their place we find nothing more wonderful than common salt dissolved in water. Other forms of neutralization that are very common are vinegar (acetic acid C2H4O2) and soda, or sour milk (lactic acid C3H6O3) and soda. When bread is "sour," we mean that there was not enough soda to neutralize the acid.
PRINCIPLES OF NEUTRALIZING ALKALIS
If we should try many experiments of neutralizing alkalis with acids, we would discover these general rules:
1 All acids contain hydrogen.
2 All alkalis contain oxygen and hydrogen in equal proportions.
3 When these substances react, the hydrogen of the acid joins the hydrogen of the base or alkali, forming water, H2O.
4 The metal of the base always replaces the hydrogen of the acid.
2KOH + H2SO4 = K2SO4 + 2H2O
Potassium hydroxid + Sulfuric acid = Potassium Sulfate + Water
(alkali or base) (acid) (Salt)
(In the above equation the potassium (K) of the potassium hydroxid replaces the Hydrogen (H) in the sulfuric acid.)
5 The other elements of the original compounds unite to form a new substance, which is neither acid nor alkali, but which is termed a salt.
The names of a few common acids, bases and salts, and their chemical formulas, are given here, as many of them will be important in the pursuance of this work.
Acids
| HCl | Hydrochloric (in gastric juice) |
| HNO3 | Nitric |
| H2SO4 | Sulfuric |
| C2H4O2 | Acetic (vinegar) |
| C6H8O7 | Citric (lemon juice) |
Bases
| NaOH | Sodium hydroxid (caustic soda) |
| KOH | Potassium hydroxid (caustic potash) |
| Ca(OH)2 | Calcium hydroxid (slaked lime) |
| NH4OH | Ammonium hydroxid |
(Ammonia gas dissolved in water produces this alkali.) The equation for this is as follows:
NH3 + H2O + NH4OH
(Ammonia) gas + Water + Ammonium hydroxid
Salts
| NaCl | Sodium chlorid (table salt) |
| KNO3 | Potassium nitrate (salt-peter) |
| CuSO4 | Copper sulfate (blue vitriol) |
| Ca3(PO4)2 | Calcium phosphate (normal) |
| (The mineral of bones) |
Fluorin, Bromin, Iodin—These three elements are in many respects like chlorin. The first is a gas, the second a heavy, Formation of salts in the human body reddish-brown liquid at ordinary temperature, and the third a dark, grayish crystalline solid. These elements all form acids just as chlorin forms hydrochloric acid. These acids produce salts, and these various salts exist in small quantities in the human body.
Mineral Sulfur—This element is of no particular importance or use to the body, as it is insoluble and cannot be digested. The compounds of sulfur, however, are numerous and important. Sulfuric acid, sometimes called oil of vitriol, is one of the most active chemicals known, and is especially destructive to living tissue, as it combines with the water in the tissue so rapidly as to char or burn it.
When sulfur is burned in air it forms sulfur dioxid, SO2, which is used for the purpose of fumigation or destroying alleged dis-ease germs. This SO2 dissolved in water gives H2SO3, sulfurous acid. By oxidizing this another part of oxygen is added, forming H2SO4. All three of these compounds are poisonous and harmful.
Hydrogen Sulfid, H2S, is a poisonous gas with a bad odor. It is formed by the decay of certain food substances, such as eggs. Sometimes this gas occurs in intestinal fermentation.
Carbon Disulfid, CS2, is used extensively to kill insects. The salts of sulfuric acid, or sulfates, are quite important, and many of them are poisonous. Glauber's salt (sodium sulfate Na2SO4) and Epsom salts (magnesium sulfate MgSO4) are extensively used by the medical profession as purgatives. These poisons cause the intestines to act violently in an effort to throw out the offending substances.
Vegetable Sulfur in the Human Body—I have herein mentioned a number of sulfur compounds which are foreign or harmful to animal life. In wonderful contrast to this is the fact that sulfur is an essential constituent of the human body, and in certain complex compounds with nitrogen and other elements, forms the brain, nerves, and many other body-tissues.
Phosphorus—This element is useful in the manufacture of common matches because it possesses the power to ignite by friction. The things of interest to the food scientist, however, are the salts of phosphoric acid. These enter largely into the bones, and to some extent into the nerves and other organs of the body.
Silicon is the element which, combined with oxygen, forms the greatest part of the rocks and the sand of the solid earth. It forms the shell of certain sea-animals. In the human body it is found in the teeth and in the bones in very small quantities.
Metals—Metals, when united with oxygen and hydrogen, form the bases of nearly all the substances studied in this lesson. When these act with acids they produce the salts. It is these salts of the metals that are of most interest to us. The salts of common metals, such as copper, tin, lead, and iron do not enter into the composition of the human body, and many of these are decidedly poisonous, especially those of copper, lead, mercury, and arsenic.
Importance of metals to digestive juices
The metals whose salts are found in the body are sodium, potassium, calcium, and magnesium. These metals in their elementary state are seldom seen outside a chemist's laboratory, but we can judge of their importance when we remember that the digestive juices contain these metals. The teeth and all bony substances are formed from these compounds, and the ability of all body-fluids to carry food material in solution depends upon a definite per cent of these metal salts. The study of minerals, or of mineral salts contained in food, together with their uses in the body, forms an important subdivision of food chemistry.
Iron—Iron is mentioned separately from other metals because it not only yields salts that occur in small quantities in the body, but because, like sulphur, it enters into the complex nitrogenous portions of the body to form part of the living substance itself.
Iron in patent medicines
This organic iron, as it is sometimes called, occurs chiefly in the red blood-corpuscles. The patent medicines which are exploited for the iron they contain, are frauds so far as nourishing the body is concerned. The popular deception is caused by the general belief that all compounds containing the same elements are alike in their uses. One might as well swallow iron filings as to endeavor to build red blood corpuscles out of the mineral solution of iron.
[LESSON III]
ORGANIC CHEMISTRY
CARBON
In this lesson I will consider carbon and carbon compounds, which are the bases of all foods and living matter. I will devote but little attention to theories and technicalities, but will discuss the subject from scientific and practical standpoints.
Wood, flesh, and other products of vegetable or of animal life blacken when heated to a sufficiently high temperature. This blackening is due to the presence of carbon. If such substances are heated with an abundant supply of air, the carbon combines with oxygen and forms a colorless gas; that is, the carbon burns.
Sources of carbon
The principal form in which carbon occurs in nature is in combination with other elements. It occurs not only in all living things, but in their fossil remains, as in coal. All products of plant life contain carbon, hydrogen, and oxygen. Among the more common of these are sugar, starch, wood, etc. Most products of animal life contain carbon, hydrogen, oxygen, and nitrogen. Among these are albumin, fibrin, casein, etc.
Carbon occurs in the atmosphere in the form of carbon dioxid or carbonic acid gas. It is also found in the earth in the form of salts of carbonic acid or carbonates, such as limestone, marble, and chalk.
Various forms of carbon
The pure element, carbon, is found in nature in the form of diamonds, which are pure crystallized carbon. Small diamonds are now made artificially in electric furnaces. Crystallized carbon also occurs in nature in the form of graphite, from which lead pencils are made. Charcoal, lampblack, and coke are forms of amorphous carbon which contain a very small percentage of impurities.
Properties of carbon
Notwithstanding the marked difference in their appearance, the various forms of carbon have some properties in common. They are insoluble in all known liquids. They are tasteless, odorless, and infusible at ordinary temperature. When heated without access of air, they remain unchanged unless the temperature is very high, in which case they unite with oxygen and are consumed, forming carbon dioxid.
INORGANIC CARBON COMPOUNDS
CARBON DIOXID (CO2)
The principal compound of carbon and oxygen is carbon dioxid, often called carbonic acid gas. This gas is always present in the air. It issues from the earth in many places, particularly in the neighborhood of volcanoes. With it many mineral waters are naturally charged.
How carbon dioxid enters the air
Carbon dioxid is constantly formed by many natural processes. Every animal that breathes gives off carbon dioxid from its lungs. This gas is also formed whenever ordinary combustible materials are burned. The natural processes of decay of both vegetable and animal matter tend to convert the carbon contained therein into carbon dioxid, which is thrown off and absorbed into the air. The process of alcoholic fermentation, and similar processes, also give rise to the formation of this gas. When fruits ripen, fall, and decay, the sugar, which all fruit-juices contain, is changed to alcohol and carbon dioxid.
RELATION OF CARBON DIOXID TO LIFE
Action of plants upon carbon dioxid
Carbon dioxid is an important factor in the life activity of the earth. The leaves of plants absorb carbon dioxid from the air, and by means of the chemical activity of the green coloring-matter or chlorophyl, the plant has the power of combining the carbon dioxid with water, and with the mineral salts which have been absorbed from the earth by the roots of the plant. Sunlight is necessary to this action, especially in the manufacture of starch.
This formation of food material in plants by the combination of simple chemical substances, such as carbon dioxid and water, is one of the fundamental life-processes. Animals do not possess this power of utilizing simple or inorganic chemical compounds, therefore they must take their food substances in the more complex forms which have been created by the power of sunlight acting upon the plant.
The wonderful carbon cycle
I have already explained how carbon dioxid may enter the air. Thus we see that the carbon dioxid which is withdrawn from the air, by the growth of plants, is constantly replaced by combustion, and in this way the "carbon cycle" is completed. This is one of the most beautiful adaptations in nature. If the plant did not remove the carbon dioxid from the air, it would soon accumulate in such quantities as to become detrimental to life, and, on the other hand, if this gas were not returned to the air by combustion, by the breathing of animals, and by the decay of plants, the vegetable world would soon be without carbon dioxid, which is as essential to plant life as is the oxygen of the air to animal life.
CARBON MONOXID (CO)
This compound is formed when a substance containing carbon is burned in an insufficient supply of air, as for example when the draught is partly shut off in a stove.
Properties of carbon monoxid
Carbon monoxid is a colorless gas. It burns with a blue flame, forming carbon dioxid. The blue flame seen playing over the embers of a coal fire is carbon monoxid burning. This gas is extremely poisonous. Carbon dioxid, CO2, is not poisonous. The poisonous properties of illuminating gas are due to the carbon monoxid which it contains.
ORGANIC CARBON COMPOUNDS
The carbon compounds thus far considered have been mentioned to illustrate a few of the simpler or inorganic forms of carbon. We will now begin the study of organic chemistry or the compounds of carbon which are commonly found only in plant and animal substances.
Combining power of carbon
Carbon has wonderful powers of combination with other chemical elements, and may combine with the same elements in thousands of different proportions. This property of carbon to form so many different compounds is considered one of the fundamental facts of chemistry upon which life depends. For example:
Carbon and hydrogen compounds
Oxygen can combine with hydrogen in but two proportions—peroxid of hydrogen (H2O2) and water (H2O)—while carbon and hydrogen can combine in more than a hundred different compounds. The simpler of these are acetylene (C2H2) and marsh gas or methane (CH4), which is the fire-damp in mines.
The compounds containing carbon, hydrogen, and oxygen number into the thousands. A great many substances formed in plants contain these three elements, such as fruit-acids, alcohol, sugar, and fats.
CLASSIFICATION OF ORGANIC CARBON COMPOUNDS
Only a few of the most important groups of the organic or life-formed carbon compounds will be considered in this work, namely:
- a Hydrocarbons
- b Alcohols
- c Glycerin
- d Aldehydes and ethers
- e Organic acids
- f Carbohydrates
- g Fats
a HYDROCARBONS
Uses of hydrocarbons in industrial chemistry
Hydrocarbons are compounds of the two elements carbon and hydrogen. These compounds are very important in industrial chemistry. They are found in petroleum, coal-tar, etc., which were originally formed from decaying and petrifying masses of plants. Gasoline, benzin, naphtha, acetylene, methane, etc., are some of the industrial forms by which hydrocarbons are known in commerce.
Coal-tar products
The industries based upon the chemistry of these hydrocarbons are very complex and interesting. Coal-tar yields, by repeated distillation and chemical reaction, thousands of compounds, many of which find important industrial usages. Coal-tar dyes are very numerous and of wonderful coloring power. They have been extensively used in the artificial coloring of manufactured foods. The Federal Pure Food Law attempted to prohibit this. In fact, it was the pernicious effect and extensive use of these poisons that stimulated the passage of the "Food and Drugs Act." Another interesting product of the coal-tar industry is saccharin. Saccharin has no food value whatever, but it is 280 times sweeter than cane-sugar, and is therefore used as a substitute in sweetening some prepared foods.
b ALCOHOLS
Varieties of alcohol
To the ordinary mind the term alcohol refers only to the intoxicating element in liquors. To the chemist, alcohol has a much broader significance. There are many varieties of alcohols, of which ethyl alcohol (C2H5.HO), which is found in liquors, is only one example. Another form of alcohol which is fairly well known is wood or methyl alcohol (CH3.OH).
Formation of higher alcohols
There are also higher alcohols, that is, those having more complex chemical formulas, such as butyl alcohol. In the fermentation of grains or fruits for intoxicating liquors, a small quantity of the various higher alcohols is formed. These higher alcohols are more intoxicating and more harmful to the human system than ethyl alcohol, and must be separated from the latter by careful distillation. The poisonous property of green whisky and cheap liquors is generally due to the presence of higher alcohols.
Alcohol does not exist in normal, fresh plant or animal substances except in very minute quantities. It is formed from sugar by fermentation. This fermentation is due to a microscopic yeast-plant.
c GLYCERIN
Another form of alcohol is glycerin (C3H8O3). It is of special interest to the food chemist because it enters into the formation of all fats.
d ALDEHYDES AND ETHERS
How formed
These are compounds containing carbon, hydrogen, and oxygen, and are closely related to alcohols. In fact they are formed from alcohols by a process of oxidation, hence contain a little larger proportion of oxygen than the related alcohol.
Uses of formaldehyde
An example of aldehyde with which many are familiar is formaldehyde, which is used in laboratories for the preservation of animal-tissues for dissection. This formaldehyde is a very strong germicide; that is, it is poisonous to bacteria or germs. For this reason it is used as a preservative of milk, a use which is forbidden by the "Food and Drugs Act," because formaldehyde is also poisonous to the human system.
Uses of ether
Ethyl ether, which is used as an anesthetic or to produce insensibility to pain, will serve as an illustration of this group of compounds. When analyzing foods in chemical laboratories, ether is commonly used for dissolving fats.
e ORGANIC ACIDS
Properties of organic acids
It will be remembered that acids were studied in the second lesson. It was found that the common properties of acids are a sour taste, ability to combine with alkalis in the formation of salts, and that all acids contain hydrogen. These same properties that were studied in the second lesson in reference to mineral acids, such as hydrochloric and sulfuric, apply also to the organic acids. The organic acids, however, as a class are not so strong or active as the mineral acids.
All organic acids are compounds of carbon, hydrogen, and oxygen, the same as alcohols and ethers, the chief difference between these compounds and acids being that the acids contain a greater proportion of oxygen. One of the simplest organic acids is formic acid (HCO.OH). This acid is the active principle in the sting of the red ant, and also of stinging nettles. It produces blisters when applied to the skin.
Process of making acetic acid
Impure acetic acid (C2H4O2) is very well known to all under the name of vinegar. Acetic acid may be obtained by distilling wood. If it could be manufactured cheaply enough, vinegar made from wood would be fully as wholesome as the best cider vinegars, but this being an expensive process of manufacture, the temptation of the food adulterator is to make the vinegar of sulfuric acid, which is much cheaper than the mild acetic acid, but much more harmful when taken into the body.
The formic and the acetic acids are examples of a series of organic acids known as fatty acids. Other members of the series are—
| Propionic acid | C3H6O2 |
| Butyric " | C4H8O2 |
| Palmitic " | C16H32O2 |
| Stearic " | C18H36O2 |
Process of making soap
These fatty acids are very important to the food scientist as they combine with glycerin to form fats. When combined with alkalis under a certain temperature they form soap. Perhaps some of our older students may remember the soap kettle on the farm at home, in which lard cracklings and other fatty fragments of the animal were boiled with lye or caustic potash to form home-made soap. The chemical action that took place was a combination of these fatty acids with the caustic potash or lye. The glycerin was set free and remained in the bottom of the kettle as soft soap. Reference will be made to these acids again, in Lesson IV, where the study of fats will be taken up in detail. (See "Fats and Oils," under Lesson IV, Chemistry of Foods, p. 122).
Oxalic acid
There are some other forms of organic acids which do not belong in the fatty series; that is, they do not contain the same general proportions of carbon and hydrogen. One of these is oxalic acid (C2H2O4) which is found in certain plants, such as sorrel, and is an active poison. Oxalic acid is used in the household for taking iron-rust out of cloth.
Lactic, malic and tartaric acids
Lactic acid (C3H6O3) is the acid of sour milk. Malic acid (C4H6O5) is found in many fruits such as apples, apricots, currants, pears, plums, prunes, etc. Tartaric acid (C4H6O6) is found principally in grapes. It is one of the constituent elements in the sediment found in wine casks, and is the active principle in cream of tartar. The latter is a potassium salt of tartaric acid.
Citric acid
Citric acid (C6H8O7) is one of the most important of the organic acids from the standpoint of the food chemist. It is the active principle of citrus-fruits, such as grapefruit, lemons, limes, oranges, etc. Lemons contain as high as five per cent of this acid. Citric acid is often used to make lemonade, and if pure citric acid is used, the manufactured product is equal to the original, except from a sentimental standpoint of having the genuine. The danger is, as in the case of adulterated vinegar, that the manufacturer may be tempted to use cheaper mineral acids instead of citric acid.
The other above-named groups of organic compounds which are formed from the three elements carbon, hydrogen, and oxygen—(f) carbohydrates and (g) fats—are very important to the food chemist. These will be considered in detail in Lesson IV. See pages [107]-[125].
ORGANIC NITROGENOUS COMPOUNDS
If to the three elements carbon, hydrogen, and oxygen, the element nitrogen is added, it still further increases the number of possible compounds that may be formed upon the base of the wonderful carbon atom. With this additional nitrogen factor, a new and a distinct quality is obtained.
The elements that make life possible
The chief characteristic of the element nitrogen is the ease with which its compounds change their chemical form. To quote the chemist, "the compounds of nitrogen are very unstable." Nearly all explosives are nitrogenous compounds. When this element, nitrogen, is combined with the wonderful variety of compounds formed by carbon, we have not only a great many intimately related yet distinct substances, but compounds which readily change from one form to another. These are the distinctive qualities or conditions necessary, from a chemical standpoint, to make the processes of life possible. Protoplasm, which is the basis of all life, is formed by an intimate mixture of a number of complex chemical compounds, the chief elements of which are carbon, hydrogen, oxygen, and nitrogen.
Importance of nitrogenous compounds
The organic compounds containing nitrogen are very numerous and very interesting. As all tissues and substances of the animal body contain nitrogen as a necessary element, we can see why this group of compounds is of great importance to the student of food science.
Some of the nitrogenous compounds which are not available as nutritive substances, and many of which are poisonous or harmful to animal life, will be considered in Lesson IX, under "Alkaloids and Narcotics." (See Vol. II, p. 349.) The principal nutritive substances, and proteids or compounds containing available food nitrogen, will be considered in Lesson IV.
[LESSON IV]
CHEMISTRY OF FOODS
Four general classes of food
The chemistry of carbon compounds and the general composition of plant and of animal substances were discussed in Lesson III. We are now prepared to take up the chemistry of food. The chemistry of food substances will be considered under the common divisions of carbohydrates, fats, proteids, and mineral salts. (See "Classification of Organic Carbon Compounds," Lesson III, p. [89].)
Classes vs. groups of related compounds
In the food tables and analyses commonly published, the above terms are used with very little explanation, and read by the average person with meager comprehension. When one reads that a food is composed of glucose, citric acid, or globulin, he is likely to become confused, not being able to understand how a food at one time can be said to be composed of carbohydrates, proteids, and fats, and at another time to be composed of other substances. The explanation is that the first classification does not refer to definite chemical substances, but to groups of related compounds having properties in common.
The different methods of analyzing food
There is still another way of giving the chemical composition of a food, namely, to specify the chemical elements that it contains. It will be remembered that the relation between chemical elements and chemical compounds was explained in the first lesson. As an example, I will take the analysis of milk. We will first say that milk contains a certain percentage of protein, carbohydrates, and fat. We might then say that the proteid of milk is part casein and part albumin, and that the albumin contains certain percentages of oxygen, sulfur, etc.; also that the chief carbohydrate in milk is milk-sugar, which in turn is composed of carbon, hydrogen, and oxygen. Or, we could consider the milk as a whole, without dividing it into groups, and give the per cent of each chemical element in the milk. Thus, the carbon of the proteid, milk-sugar, and fat would be all considered together, and show a certain per cent of carbon in the milk as a whole.
CARBOHYDRATES
The word carbohydrate means carbon combined with water; that is, the element carbon is combined with hydrogen and oxygen, which exist in the carbohydrate compound in the same proportion as they exist in water.
The carbohydrates are closely related chemically to the aldehydes and the alcohols, so far as their composition is concerned (See "Aldehydes and Ethers," Lesson III, p. [93]), but this does not imply that they have the same physiological effect in the animal body.
CLASSIFICATION OF CARBOHYDRATES
The carbohydrates are divided by the chemist into three classes known as
- a Monosaccharids
- b Disaccharids
- c Polysaccharids
The principal subdivisions found in these classes of carbohydrate foods are given in the following table, arranged in the order of their importance:
| Monosaccharids | Disaccharids | Polysaccharids |
|---|---|---|
| 1 Glucose or grape-sugar | 1 Cane-sugar | 1 Starch |
| (formerly called dextrose) | ||
| 2 Pentoses | 2 Maltose | 2 Glycogen |
| (of which there are several) | 3 Lactose | 3 Cellulose |
| 3 Levulose | 4 Gums | |
| 4 Galactose | 5 Inulin |
a MONOSACCHARIDS
1 GLUCOSE OR GRAPE-SUGAR (C6H12O6)
Glucose or grape-sugar is the most important sugar known from the standpoint of the physiological chemist. This sugar is normally found in considerable quantities in human blood, and is absolutely essential to the life-process, a fact which forms an amusing contrast with the popular conception of the term glucose as something injurious or poisonous.
Sources of glucose
Glucose is found in honey, and in nearly all fruits, grains, and sweets. (For "Sweets" see Lesson VIII, Vol. II, p. 324). It may be taken into the human body directly from such fruits, or it may originate by the digestion of other carbohydrates.
Pure glucose crystallizes and resembles cane-sugar, but is not so sweet. The glucose of commerce, sold as sirup, is a product manufactured from corn, or other starches, and will be considered more in detail under the heading starch. (See "Polysaccharids," p. [114]).
2 PENTOSES (C5H10O5)
Sources of pentoses
Pentoses form a group of sugars, the chemical formula of which contains five atoms of carbon. Each different pentose could be studied in detail by the chemist, but the pentoses are of no particular interest to the food scientist. They exist, however, in the coarse parts of plants, such as stalks and leaves, and are of considerable importance in animal feeding. From the standpoint of human food we will remember that the carbohydrates of green plants contain a percentage of these pentoses, but as they are never removed from the plant separately, as are other sugars, we must consider their physiological effect in the particular plant rather than separately.
3 LEVULOSE (C6H12O6)
This is the companion sugar to glucose and exists in many fruits. Levulose is often called "fruit-sugar." The composition of levulose is exactly the same as glucose, but the atoms are combined in different ways.
Levulose, for all practical purposes, may be considered the equivalent of glucose in the human body. It is sweeter than glucose and more closely resembles cane-sugar.
4 GALACTOSE (C6H12O6)
Galactose, which is of the same composition as levulose, is another companion sugar to glucose, and is formed by the digestion of lactose or milk-sugar.
b DISACCHARIDS
1 CANE-SUGAR (C12H22O11)
Just as there are three monosaccharid sugars with six carbon atoms each, so there are three disaccharid sugars which have twelve carbon atoms each. The first of these is cane-sugar. It is commercially made from either sugar-cane or sugar-beets, and is identical in chemical composition from either source.
Cane sugar, when digested in the human body, or by artificial means, combines with water, and forms glucose and levulose, as shown by the following equation:
C12H22O11 + H2O = C6H12O6 + C6H12O6
Cane-sugar + Water = Glucose + Levulose
2 MALTOSE (C12H22O11)
Maltose—how formed
Maltose is the second member of the disaccharid group, and is of the same composition as the other two. Maltose derives its name from malt. It is formed from the starch of grains by a process of digestion which may be performed in the animal body, or by the process of malting. Maltose, like cane-sugar, can be further digested into monosaccharid sugars, but upon such digestion, instead of forming two separate simple sugars, it is wholly converted into glucose.
The reader will now understand the meaning of the terms monosaccharid, disaccharid, and polysaccharid. MONO, which means one, is the simplest form of carbohydrates. Disaccharids (DI, meaning two), split up to form two simple sugars. Polysaccharids (POLY, meaning many) are complex compounds which form many simple sugars.
3 LACTOSE (C12H22O11)
Lactose exists in milk and has the same formula as cane-sugar. Milk contains about five per cent of this sugar.
When lactose is digested it combines with water as does cane-sugar, but instead of yielding glucose and levulose, it yields glucose and galactose.
c POLYSACCHARIDS
1 STARCH
The chemical formula of starch and other polysaccharids is written (C6H10O5)n. This means that the proportion of the elements is according to the figures given, but the number of atoms that are supposed to be combined is many times greater than five, and is not accurately known. This is purely theoretical, and of no practical importance, except that it shows that the polysaccharid is capable of being digested or broken up into many simple carbohydrate compounds.
Sources of starch
Starch is the most abundant carbohydrate known. It is the chief constituent of all cereals, and is found in large quantities in green fruits and tuberous plants. Starch occurs in small granules, varying greatly in size in different foods.
Potato starch
Potatoes are composed chiefly of starch and water. The starch grains of potatoes can almost be distinguished with the naked eye. These starch granules are not atoms or molecules in the chemical sense, but are small receptacles in which starch has been deposited by the growing plant. When cooked or boiled in water these starch grains swell into a mushy, pasty or gelatinous mass; when cooked in dry heat until they begin to turn brown, they are changed into a compound related to the gum group, known as dextrin.
Solubility of starch
Starch does not dissolve in water as do sugars. If starch is treated with digestive fluids, such as saliva, or with certain acids, it goes through a complex process of digestion in which it is first turned into soluble starch, then into the various forms of dextrin or gums, and finally into maltose or malt-sugar.
How corn-starch is changed into glucose
Corn-starch, treated with weak sulfuric acid, changes the starch into glucose. The ordinary glucose or corn-sirup is not all changed by this process, into pure glucose, but contains some maltose and other gummy compounds; hence it will not crystallize or granulate into pure sugar. After the acid has changed the starch into glucose it (the acid) is neutralized with an alkali. A crude compound is thus formed, which settles to the bottom of the tank, and from which the glucose can be easily separated. Commercial glucose is now very extensively used in the manufacture of various food products, especially confectionery. Pure glucose is a wholesome food, but there is some danger that the commercial product may (due to carelessness in manufacturing, or to the use of cheap and impure acid) contain various mineral poisons. Government testing of glucose and similar manufactured products is, in the writer's opinion, fully as essential as the government inspection of packing-house products.
How starch is changed into maltose
Just as glucose may be manufactured from starch treated with dilute acids, so maltose may be made by treating starch with malt. The brewing of beer depends upon the chemical changes induced in starch by malt. Barley is ordinarily used for this purpose. The barley is sprouted in a warm, damp room, and a process of starch digestion begins, which is necessary in order that the young barley sprouts may grow. This changes the starch into maltose. The digestive principle developed in the barley-malt may be utilized to malt other grains by mixing them with the sprouted barley.
Maltose in foods
If this process of malting is stopped at the proper time, and the sugar dissolved, and extracted, a product is formed consisting chiefly of the sugar maltose. This is the basis of malt extract, malt honey, and many similar foods put on the market, which are claimed by the manufacturers to have wonderful dietetic and curative values.
2 GLYCOGEN
Glycogen—how formed and where stored
Glycogen is commonly called animal-starch. It exists in the liver in small quantities. All carbohydrates are digested in the alimentary canal and absorbed into the blood in the form of simple sugars of the glucose group. When these sugars reach the liver they are again built up into a complex carbohydrate very similar to starch in composition. This glycogen or animal-starch is stored in the liver until the body has need of it, when it is changed into glucose and given back to the body in the form of energy. (See "Metabolism of Carbohydrates," Lesson VI, p. [202]).
3 CELLULOSE
Cellulose—its purpose, source, and importance
Cellulose, from the standpoint of human nutrition, is not a food product, being insoluble by the digestive juices, but it is very important in the digestion and the alimentation of other foods. Its chief purpose is to excite stomach and intestinal peristalsis. All plant products in their natural form contain some cellulose, though the percentage is very small in such grains as rice and barley. The bran of wheat or of corn is chiefly cellulose. Wood is almost pure cellulose.
Cellulose can be digested by strong acids into simple carbohydrates, in the same way that starch may be. Sugar can be manufactured from wood or rags, but the process is yet too expensive to be applied commercially. Some of us may live to see the time when the chief food of mankind will be manufactured from scrap lumber and waste paper. Bacteria have the power of digesting cellulose. The bacterial action or fermentation in the human intestines may cause a small amount of cellulose to be digested, but the quantity is of no consequence from a nutritive point of view.
4 GUMS
The gums include a group of rather complex carbohydrates which are intermediate between starches and sugars. From plants are derived many varieties of gums which have various commercial uses in the market, such as gum arabic.
I have already spoken of the formation of dextrin from starch. Dextrin has no particular dietetic qualities that do not exist in starch. It is, in fact, starch arrested at an intermediate point of digestion.
Pectins in fruits
Pectins are a group of gummy substances found in fruits, especially green fruits which are in the process of being formed into sugar. These pectins form the basis of fruit jellies. Green grapes, as every housewife knows, will make better jelly than ripe grapes. This is because the pectins in ripe grapes have been transformed into sugar. The pectins in fruit are in most cases wholesome enough, though it would seem the better part of wisdom to eat all fruits in the ripened state, after Nature has completed her work.
5 INULIN
Inulin is a compound closely related to starch, and upon digestion with acids, yields levulose just as starch yields glucose. It is of no particular interest to the food chemist, as it exists in but very small quantities in starch, and has no distinct dietetic value.
FATS AND OILS
Composition and formation of fats and oils
The fats and oils in food products, whether of plant or animal origin, contain the elements carbon, hydrogen, and oxygen. These fats are formed by uniting the fatty acids with glycerin, which belongs to the alcohol group. The particular fat that is formed takes its name from the acid which enters into its composition; thus stearic acid unites with glycerin to form the fat stearin.
The following table gives the names of a few of the more common fatty acids and their corresponding fats:
| Stearic acid ... ... | Stearin |
| Palmitic acid ... ... | Palmitin |
| Oleic acid ... ... | Olein |
| Butyric acid ... ... | Butyrin |
Distinction between tallow and lard
A fat from any source will usually contain several of these chemical compounds. The ordinary animal fats, such as tallow and lard, are formed chiefly of the two fats stearin and olein. The different proportions of these fats will determine the melting point or hardness of the mixed product. Olein is a liquid at ordinary temperature, while stearin is solid. The reason that tallow is a firmer fat than lard or butter is because it contains a larger per cent of stearin.
Olive-oil, cottonseed-oil, and other vegetable oils contain large per cents of olein, which accounts for their being liquid at ordinary temperature.
Dairy butter vs. artificial butter
Butyrin is a fat found in small quantities in dairy butter, and does not exist in cottonseed-oil and other fats from which oleomargarin is manufactured. This is the reason that artificial butter lacks the flavor of the dairy product, and this is remedied to some extent by churning the fats of the cottonseed-oil and tallow with fresh cream, which imparts a small quantity of the butyrin and similar compounds to the oleomargarin and gives the characteristic flavor of butter.
Oils as active poisons
Besides the more common fats herein mentioned there are many other fats that exist in certain vegetable oils in small proportions. These fats give the oils their characteristic properties, and may render them unfit for food. Some oils are active poisons, such as croton-oil, which is the most powerful physic known. The power of all physics and cathartic drugs is measured by the active poisons they contain.
Packing-house uses of stearin and olein
When fats are heated to a high temperature they decompose and form various products, some of which are irritating and poisonous to the human system. In the manufacture of packing-house and cottonseed products the stearin is often separated from the olein. The granular appearance of pure leaf lard is due to crystals of stearin. In the packing-house stearin is separated from the tallow in large quantities. The stearin is used to make candles, etc., while the olein is used for food purposes in this country in the form of oleomargarin, while in Europe it is used under its right name as a cooking product. It is equally as wholesome, if not more so, than lard.
Rancid fats made edible
Fats may become rancid; this is caused by the decomposition of fat due to its uniting with the oxygen of the air. Rancid fats and nut-kernels can be restored and made edible by heating them in an oven until the oxidized fat is neutralized by the heat.
PROTEIDS OR NITROGENOUS FOOD SUBSTANCES
Proteids defined
The food substances which contain nitrogen are commonly called proteids, or, if these compounds are considered together, the name protein may be given the group. Protein is not a single compound, but includes all substances which contain the element nitrogen in such combinations as are available for assimilation in the human body.
Only proteid foods contain nitrogen
Protein is the most important group of nutrients in the animal body. The proteid substances in the body must be formed from proteids taken in the form of food, because only proteid foods contain the element nitrogen. All proteids contain nitrogen, but all nitrogen does not contain protein. All proteids, therefore, are nitrogenous compounds.
Formation of organic nitrogen
The animal body does not possess the power of combining elementary nitrogen with other elements. Bacteria have the power to utilize the nitrogen of the air to form mineral salts or nitrates. Plants have the power to unite the nitrogen derived from these nitrates with carbon, oxygen, and hydrogen. In this way organic nitrogen, or proteids, are formed. The animal body may digest these proteids, however, and transform them into other proteid compounds. All proteids contain carbon, hydrogen, oxygen and nitrogen; most of them contain sulfur, and a few contain phosphorus, iron, copper, and bromid.
The percentage by weight of the various elements which form proteid matter is about as follows:
| Carbon ... ... | 52% |
| Hydrogen ... ... | 7% |
| Oxygen ... ... | 22% |
| Nitrogen ... ... | 16% |
| Sulfur ... ... | 2% |
| Phosphorus ... ... | 1% |
The following table gives three groups of proteid substances:
| Simple Proteids | Compound Proteids | Albuminoids |
|---|---|---|
| Albumins | Respiratory pigments | Collagen |
| Globulins | Gluco Proteids | Gelatin |
| Nucleo albumins | Nucleins | Elastin |
| Albuminates | Nucleo proteids | Reticulin |
| Coagulated proteids | Lecith albumins | Keratin |
| Proteoses (Albumoses) | ||
| Peptones |
Amido compounds
Besides these real proteids there are a few substances known as amido compounds which exist in small quantities in vegetables, and a number of nitrogenous substances which exist in meat and meat extracts, which are not true proteids, as they have little or no nutritive value, but act as stimulants or irritants in the body.
Ptomains—how formed
Ptomains are another class of substances which are often found in food products. They are formed by the growth of bacteria, and are in reality the nitrogenous waste-products of bacterial life. Ptomains develop in meats and dairy products held in cold storage, and are sometimes the cause of serious poisoning. Nitrogenous waste-products will be further discussed in Lesson VI, under "Metabolism of Proteids." (See p. [209.])
Sources, coagulation and solubility of albumin
Albumin is one of the commonest and simplest forms of proteids known. It is found in the white of eggs, in milk, and in blood. It is coagulated by heat, and by certain chemicals, such as acids, alcohol, and strong alkalis. Albumin is soluble in water and in weak solutions of salt, but it is not soluble in very strong salt solutions.
Sources and properties of globulins
Globulins are much like albumin, but are not soluble in water. They are, however, soluble in dilute salt solutions. Globulins exist in considerable quantities in the yolk of eggs, and in the blood. The globulin in the body could not remain in solution if there were not always present a small quantity of salt in the blood. There are several types of globulins. The fibrinogen of the blood, which coagulates, forming clots, when the blood is exposed to the air, is a globulin. Hemoglobin, which is the chief component of red blood-corpuscles, and which unites with the oxygen in the lungs and carries it to the various tissues of the body, is another form of globulin, and one which contains a considerable amount of iron.
Sources of casein
Casein is the most important proteid substance in milk, and is familiar to all as the curd or white substance of clabbered milk. A related form of vegetable casein is found in leguminous seeds, such as beans and peas.
Sources of proteoses and peptones
Proteoses and peptones are proteids that are formed by the digestion of other proteids. They exist in the alimentary canal in the partly digested food. Peptones are readily soluble, and for this reason are easily absorbed through the walls of the digestive organs. (See Lesson V, "Digestive Organs"—[The Stomach], p. [137;] also "Composition of Gastric Juice," p. [147]).
MINERAL SALTS IN FOOD
Vegetable mineral salts vs. common table salt
The subject of salt in food has received considerable attention and discussion by scientific investigators, and many theories have been advanced by those interested in hygiene as to the effect of common salt used in food. The tissues and organs of the body contain certain salts, without which life could not exist, but it does not follow that these salts need to be supplied in mineral form. Common table salt is an inorganic substance, while the mineral salts in green and fresh vegetables are organic, and readily convertible, therefore a valuable aid in the digestion of other foods. A diet of sugar, pure oil, and artificially prepared proteids would be absolutely unwholesome and would fail to nourish the body for any length of time because of the lack of mineral salts. Foods containing mineral salts All natural food products, whether of vegetable or animal origin, contain a limited but ever-present amount of mineral salts. This is especially true of milk, eggs, and the seeds and green portion of plants. The amount of salts in the human body is considerable, especially the calcium phosphates of the bones, but the salts that need to be supplied daily in food is small because the salts are not consumed as rapidly as are other elements of nutrition.
Grains deficient in salt
Some grains, especially rice and corn, are somewhat deficient in salts. At the Kansas Experiment Station some pigs were fed exclusively on corn, and others on grain and green forage. At a certain age the pigs were killed, and the bones weighed and tested for strength. The bones of the pigs which had been fed on a corn diet, which is deficient in mineral salts, were about half as heavy and strong as the bones of the pigs fed in a more natural way.
[LESSON V]
CHEMISTRY OF DIGESTION
DIGESTIVE ORGANS AND DIGESTIVE JUICES
First—THE MOUTH:
The three salivary glands of the mouth secrete the saliva, which is an alkaline substance containing a digestive enzym called ptyalin.
The saliva begins the digestion of starch and moistens food to facilitate swallowing.
Second—THE STOMACH:
The gastric juice secreted by the mucous lining of the stomach is an acid. It contains hydrochloric acid and pepsin, which act on proteids, changing them to proteoses ("intermediate products formed naturally in the process of digestion") and peptone.
The gastric juice also contains rennet, which acts directly on milk, and indirectly on all proteids.
Third—THE LIVER:
The liver secretes a digestive fluid called bile, which is an alkaline substance. Its chief purpose is to emulsify fats and to supply the alimentary tract with the requisite amount of moisture.
Fourth—THE PANCREAS:
The pancreatic juice, secreted by the pancreas, is an alkaline and slightly acidulous substance. It contains three enzyms, the names and action of which are as follows:
Amylopsin completes the digestion of starch.
Trypsin completes the digestion of proteids.
Steapsin converts fats into fatty acids and glycerin.
Fifth—THE SMALL INTESTINES
The intestinal juices secreted by the small intestines are alkaline substances which change sugar and maltose into glucose, and perform the last step in the process of breaking up or subdividing food so fine that it will pass through the intestinal walls into the circulation.