[Illustration:  A DROP OF IMPURE WATER MAGNIFIED.]

8.  Alcohol (al’-co-hol).—­All of you know something about alcohol.  Perhaps you have seen it burn in a lamp.  It will burn without a lamp, if we light it.  It is so clear and colorless that it looks like water.  The Indians call it “fire-water.”  Alcohol differs very much from foods.  It is not produced from plants, as fruits and grains are; neither is it supplied by Nature ready for our use, as are air and water.

9.  Fermentation.—­When a baker makes bread he puts some yeast in the dough to make it “rise,” so the bread will be light.  The yeast destroys some of the sugar and starch in the flour and changes it into alcohol and a gas.  The gas bubbles up through the dough, and this is what makes the bread light.  This is called fermentation (fer-men-ta’-tion).  The little alcohol which is formed in the bread does no harm, because it is all driven off by the heat when the bread is baked.

[Illustration:  FERMENTATION.]

10. Any moist substance or liquid which contains sugar will ferment if yeast is added to it, or if it is kept in a warm place.  You know that canned fruit sometimes spoils.  This is because it ferments.  Fermentation is a sort of decay.  When the juice of grapes, apples, or other fruit is allowed to stand in a warm place it “works,” or ferments, and thus produces alcohol.  Wine is fermented grape-juice; hard cider is fermented apple-juice.

11. Beer, ale, and similar drinks are made from grains.  The grain is first moistened and allowed to sprout.  In sprouting, the starch of the grain is changed to sugar.  The grain is next dried and ground, and is then boiled with water.  The water dissolves the sugar.  The sweet liquid thus obtained is separated from the grain, and yeast is added to it.  This causes it to ferment, which changes the sugar to alcohol.  Thus we see that the grain does not contain alcohol in the first place, but that it is produced by fermentation.

12. All fermented liquids contain more or less alcohol, mixed with water and a good many other things.  Rum, brandy, gin, whiskey, and pure alcohol are made by separating the alcohol from the other substances.  This is done by means of a still, and is called distillation.

[Illustration:  DISTILLATION.]

13. You can learn how a still separates the alcohol by a little experiment.  When a tea-pot is boiling on the stove and the steam is coming out at the nozzle, hold up to the nozzle a common drinking-glass filled with iced water, first taking care to wipe the outside of the glass perfectly dry.  Little drops of water will soon gather upon the side of the glass.  If you touch these to the tongue you will observe that they taste of the tea.  It is because a little of the tea has escaped with the steam and condensed upon the glass.  This is distillation.

14. If the tea-pot had contained wine, or beer, or hard cider, the distilled water would have contained alcohol instead of tea.  By distilling the liquid several times the alcohol may be obtained almost pure.