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.