Sugar is a general name applied to a class of bodies composed of carbon, oxygen, and hydrogen, having a more or less sweet taste, and exercising a rotatory power on the plane of polarized light.
In chemical composition the sugars may be regarded as a combination of water with carbon, and they belong therefore to that class of bodies which are known as carbo-hydrates. Starch, wood-fiber, and various sorts of gums are bodies nearly allied in chemical composition to sugar.
Sugar is chiefly a product of vegetable growth, and is found in some part or other of a large number of substances.
Sometimes it is found in the root, as in the beet and sweet-potato. Again, it occurs in the fruit, as in the grape and water-melon. At other times it is stored in the juices of the plant, as in the maple-tree and the sugar-cane.
In whatever position it occurs, it is always diluted with water, and mixed with various gums and albuminous bodies peculiar to the plant containing it.
The manufacture and refining of sugar consist in separating it from these impurities, and evaporating the water until the crystallizing point is reached, or a sirup is produced.
I have said that sugar is of vegetable origin. This must be construed to mean the sugars of commerce and common consumption. The animal organism possesses a glycogenic function in common with plants.
The amount of sugar, however, produced by the animal organism, with the exception of that from the milk-glands, is inconsiderable in a state of health. In certain forms of disease, however, as in diabetes mellitus, the amount of sugar produced in the body may be immensely increased.
Sugar may also be made by chemical means from the bodies already mentioned, such as starch, cellulose, gum, etc.
In this sketch I will mention only the more important sugars. For the purposes of a popular classification the sugars may be arranged as follows:
1. Cane-sugar, or sucrose.
2. Grape-sugar, or glucose.
3. Milk-sugar, or lactose.
4. Starch-sugar, or amylose.
Cane-sugar, in a commercial sense, is by far the most important of these bodies.
It has never been formed by chemical synthesis, and the chief sources from which it is derived are the sugar-cane, the sugar-beet, and the sugar-maple. When pure it is a white crystalline body easily soluble in water and having an intensely sweet taste. The molecule of cane-sugar consists of forty-five atoms, distributed as follows, viz., twelve atoms of carbon, twenty-two of hydrogen, and eleven of oxy-