Page:Popular Science Monthly Volume 70.djvu/254

250 the process follows the outline laid down by Berthelot. This amounts to making our alcohol out of charcoal and water, and electrical energy derived from water power, with the assistance of some chemical reagents, which can be recovered and used over again. The process is simple and practical, but it costs considerably more to make alcohol this way than by fermentation, therefore there is no likelihood that installations on this plan will be put into operation yet awhile.

Now and then articles appear in the newspapers with such titles as 'Alcohol from Sawdust,' or 'Alcohol from Old Newspapers,' titles calculated to rouse the interest (perhaps the cupidity also) of readers, and conveying the impression that here at last is a new and brilliant discovery. There is nothing very new about it. Alcohol was first made from wood about one hundred years ago, and chemists have turned their attention sporadically to improving the methods ever since.

In round numbers 50 per cent, of the weight of wood is cellulose, a substance containing the same elements, in the same proportions by weight, as starch. Starch, under the influence of a suitable enzyme, or of a dilute acid, can be converted to fermentable sugar; and so can cellulose, although with greater difficulty and much less completely. Newspapers are made from wood pulp and are almost wholly cellulose. Many other things are largely cellulose, for instance, corn stalks, linen, hemp, flax, cotton (cotton wool is practically pure cellulose). From any of these ethyl alcohol may be made, indeed, Melsen of Brussels, as long ago as 1855, appears to have amused himself by seeing how long a list of substances he could compile from which he could say he had made ethyl alcohol. His list included, besides those materials already mentioned, such things as dead leaves, stubble, straw, chaff, sweepings from malt, carrot tops, sponges, even birds' nests!

A complete history of all the partial successes would be tedious to any but professional chemists. The difficulty has always been, and still is, that only a small percentage of the cellulose present can be converted into fermentable sugar. This means that large quantities of material must be handled, large amounts of acids must be used, a great deal of fuel must be burned in heating these large quantities, and, after all, a relatively small amount of alcohol is obtained. If a weight of alcohol equal to 7 per cent, of the weight of the wood is secured, the yield must be considered good. Even this sounds promising because wood is cheap. But it should be understood that it is not the cost of the raw material which constitutes the obstacle; it is the cost of treatment.

Simonsen's and Classen's processes may be taken as illustrative of the best present methods for making ethyl alcohol from wood. They are being tried on a commercial scale in Germany.