FIG. 173.—VACUUM PAN FOR EVAPORATING THE SYRUP TO PRODUCE SUGAR.
In the process of refining, 2 or 3 parts of raw sugar, with one of water containing a little lime, ground bone black, and the serum of bullocks’ blood, is heated by the passage of steam through it. The albumen of the serum coagulates and rises to the surface in a scum which entangles the impurities and bone black, leaving the syrup light in color. The latter is then filtered through bone black until it is colorless and is then evaporated in the vacuum pan, which is the important invention of the century in sugar making. Heat has the effect of converting the crystallized sugar into the uncrystallized variety, and hence the evaporation must, to prevent this, be conducted at a low temperature. Contact with the air is also objectionable. These conditions are provided for by conducting the evaporation in a vacuum, which lowers the evaporating temperature and avoids contact with the air. The vacuum pan was the invention of Howard, an Englishman. (British Pat. No. 3,754, of 1813). As constructed to-day it is an enormous vessel (see [Fig. 173]), capable of holding 7,000 or more gallons, and yielding 250 barrels of sugar at a strike. In this a vacuum is maintained by a condenser, the vapors passing from the pan to the condenser through the great curved pipe rising from the top, which pipe is five feet in diameter. A gentle heat is applied through internal steam-heated coils which connect with an external series of steam inlet pipes on one side, and a corresponding series of steam outlet pipes on the other. A large discharge valve for the concentrated syrup closes the bottom of the pan. After concentration the crystallized sugar is separated from the syrup by a centrifugal filter, in which the liquid is thrown from the crystallized sugar by centrifugal action. The first centrifugal filter is shown in British patent to Joshua Bates, No. 6,068, of 1831. This, however, revolved about a horizontal axis. The present form of centrifugal filter is a cylinder revolving about a vertical axis, the sides of the cylinder being formed of filtering medium, through which the liquid is thrown by centrifugal action, while the sugar is retained within. This was the invention of Joseph Hurd, of Mass., U. S. Pat. No. 3,772, Oct. 3, 1844; re-issue No. 607, Sept. 29, 1858, which patent was extended for seven years, from Oct. 3, 1858. The diffusion process, which extracts the juice by cutting the cane in slices and soaking in water; the bagasse furnace, which dries and burns the expressed cane stalks as fuel, and the manufacture of glucose and grape sugar by the reaction of sulphuric acid on starch, are interesting allied features of this industry which can only be briefly mentioned. Most of the sugar consumed in the United States is imported, much raw sugar being imported and refined here. The imports for the year 1899 were 3,980,250,569 pounds, and the per capita consumption in 1898 was 61.1 pounds a year.
Aids to Digestion.—It is only during the last part of the Nineteenth Century that the world has learned how to live. “What is one man’s food is another man’s poison” has been a trite old saying for many years, but the reason why has only in late years been fully understood. The physiology of digestion, the relative digestibility of different articles of food, and their nutritive values, have received of late years the earnest attention of physicians and students of dietetics and have contributed much to the quality and kind of food, and a knowledge of when and how to eat it. We know that the starchy foods are digested by the saliva, which is an alkaline digestion; that meat, fish, eggs, cheese and the albumenoids are digested in the stomach by the gastric juices (pepsin and hydrochloric acid) which is an acid digestion, and that the remaining portions of starch, the sugars, and fats are digested in the intestines, and that this is also an alkaline digestion, and this has helped to solve the problem for us. We also know that starch is an excellent food, provided the vital powers are sufficiently stimulated by fresh air, sunlight, and exercise to digest it, as do the horse and the ox when they eat corn, but we know furthermore that the sedentary occupations of modern life leave many stomachs in a condition unable to assimilate starch, and so bread, oatmeal, potatoes and such simple staples, instead of nourishing the body, ferment in the enfeebled stomach, produce acids and gas, and lay the foundation for serious chronic diseases. The student of chemistry and dietetics knows to-day that one part of diastase will effect the conversion of 2,000 parts of starch into grape sugar, as a preliminary step to its digestion, and so by treating starchy matter with substances containing diastase (derived from malt) a partial transformation is effected which will materially shorten and assist its digestion. This fact has been largely made use of in the preparation of easily soluble or pre-digested foods, examples of which are found in patent to Horlick (malted milk), No. 278,967, June 5, 1883; to Carnrick (milk-wheat food), Dec. 27, 1887, No. 375,601; and Boynton and Van Patten (cereals and diastase), 344,717, June 29, 1886.
Beverages.—Pure water, nature’s own gift, has ever supplied every legitimate need of the human race, but civilized life has greatly extended its list of drinks, much to its own detriment. Soda water, whiskey, beer, ginger ale, tea, coffee, and chocolate represent enormous industries, and probably all do more harm than they do good. Much inventive genius in the Nineteenth Century has been bestowed upon the soda water fountain, on stills, and processes for aging liquors and processes for brewing beer, on cider and wine presses, on bottling machines and bottle stoppers, on devices for carbonating waters, and in coffee and teapots. The trend of the times is shown in the following figures, which represent the per capita consumption of beverages in the United States for 1898: tea, .91 of a pound; coffee, 11.45 pounds; wines, .28 of a gallon; distilled spirits, 1.10 gallons; and malt liquors 15.64 gallons. The largest per capita increase since 1870 has been in malt liquors, and the next in coffee. In tea and distilled spirits there has been a decrease, while the consumption of wines is the smallest of all and has varied but little.
[CHAPTER XX.]
Medicine, Surgery, Sanitation.
[Discovery of Circulation of the Blood by Harvey]—[Vaccination by Jenner]—[Use of Anæsthetics the Great Step of Medical Progress of the Century]—[Materia Medica]—[Instruments]—[Schools of Medicine]—[Dentistry]—[Artificial Limbs]—[Digestion]—[Bacteriology, and Disease Germs]—[Antiseptic Surgery]—[House Sanitation].