Page:Popular Science Monthly Volume 70.djvu/253

Rh little lower in temperature than the one beneath it. The alcohol vapor and water vapor from the still beneath pass through this dephlegmator, and it is readily seen that much of the water and some of the alcohol must condense in it and trickle back into the still. Inasmuch as alcohol condenses at a lower temperature than water it has the better chance to pass clear through, and into the condenser and receiver. Many modifications of this machine are on the market and they are all efficient. It is an easy matter, with it, to obtain 80 per cent, to 90 per cent, alcohol, and not difficult to obtain 95 per cent, alcohol. The last four or five per cent, of water clings hard to the alcohol and can not be removed by distillation alone. If it is desired to make yet purer alcohol, some substance such as lime, which combines eagerly with water, must be added to hold the water back, and then practically pure alcohol may be distilled off. Pure alcohol containing no water (100 per cent.) is known as absolute alcohol. But such pure alcohol is needed only for a few special chemical processes; there is no general demand for anything better than 95 per cent. Indeed, absolute alcohol has what may be called an avidity for water; it is hygroscopic, and if left in an open bottle will soon collect moisture out of the air and dilute itself.

It is evident that any distillery in the country—and there are about one thousand of them producing upwards of one hundred and fifty millions of 'tax gallons' a year—can increase its output to correspond to the demand which may spring up. The permission to market the product free of tax, if denatured, will then, in the first instance, merely furnish another outlet for the products of these distilleries. A new factory will find itself immediately in competition with the old established plants.

The question next arises, are there any methods of making alcohol other than those by which spirituous liquors are made? In the sense that spirituous liquors are essentially nothing but more or less dilute alcohol such other methods are obviously impossible. But there are methods starting with very different raw materials.

Berthelot, the French chemist, long ago showed how ethyl alcohol might be made synthetically from inorganic materials. The destructive distillation of coal gives us coal gas, and one of the constituents of this is ethylene. This ethylene will dissolve in sulphuric acid forming ethyl-sulphuric acid. If we add water and distil, ethyl alcohol is given off and collects in the receiver, while the sulphuric acid may be recovered in its original condition. At the present time we can start even farther back than Berthelot's starting point. A mixture of lime and charcoal heated in an electric furnace will give us calcium carbide. This calcium carbide, with water, will give us acetylene, and the acetylene will combine with hydrogen to form ethylene. Then the rest of