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Page:Popular Science Monthly Volume 21.djvu/517

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503
THE CHEMISTRY OF SUGAR.

Honey is composed of left-handed or invert-sugar, some grape sugar, and more or less cane-sugar. After keeping for some time the cane-sugar is all converted into the invert variety. When cane-sugar is heated to a temperature of about 200° C, it undergoes a transformation, and a part of it is changed into an aromatic substance called caramel. This change consists essentially in the loss of two molecules of water. Caramel is used chiefly in the manufacture of candies, for flavoring: whiskies, brandies, etc.

A pleasing and instructive experiment which any one can try will show that sugar is made of charcoal and water. A strong solution of sugar is placed in a glass until the bottom is well covered. Strong sulphuric acid (oil of vitriol) is now added, and the whole stirred with a glass rod until it swells up and turns black. The sulphuric acid has a very strong liking for water, which it steals from the sugar molecules, leaving only the carbon.

Another interesting experiment is to burn the carbon in sugar with the oxygen in the chlorate of potassium, the lire being kindled with a drop of sulphuric acid. For this experiment four parts of sugar are carefully mixed in an old saucer with five parts of chlorate of potassium, and the mass then touched with a glass rod which has been dipped into strong sulphuric acid. The chemical action produced by the sulphuric acid makes heat enough to ignite the whole mass, and the carbon of the sugar is thus burned out.

Grape-sugar, as its name implies, is found in grapes and some other substances. This name is also sometimes incorrectly given to one, and often all the sugars made from starch or derived from fruits. It is dextro-gyratory, having for the sodium ray a specific rotatory power of about 52·5°. It is fermentable, and is not changed by heating with dilute acids. It crystallizes, but with less facility than cane-sugar, and is much less sweet to the taste. There are other varieties of sugar which possess the same properties as grape-sugar. To these the general name, dextrose or glucose, has been given. Any sugar, whatever be its source, which, in a dry state, has the formula C6H12O6, and a specific rotatory power of 52·5° to the right, is entitled to the name dextrose.

Dextrose is also the final product of long-continued boiling of starch with an acid.

Starch-sugar, or amylose, is a mixture of various products, chief among which are dextrose, dextrine, and maltose.

For a full discussion of this sugar I refer to my paper in this magazine for June, 1881.

Milk-sugar, or lactose, is found in milk, and is not important commercially. It is used mostly as a vehicle for administering-medicines. In composition it is identical with cane-sugar, but differs from it greatly in both chemical and physical properties.

Optically it is nearly related to dextrose, its specific rotatory power