Page:Popular Science Monthly Volume 85.djvu/592

588 —until now largely a chemical curiosity—would perhaps never have been thought of for any technical purpose. Undoubtedly many other industries will avail themselves of this new source of oxygen under conditions similar to those on submarines, for example, for diving operations, in mines, for caisson work, etc.

Militarism in the search for new explosives discovered guncotton and thereby started the "nitrocellulose" industry. While guncotton made by the treatment of cotton with nitric acid proved to be an almost uncontrollable explosive, it was soon found that by a less energetic action of nitric acid on cotton, substances could be produced which were practically free from any danger of explosion. These lesser nitrated cotton products became the starting material for the celluloid industry in all its interesting and important branches. Besides furnishing various well-known household articles, billiard balls, etc., and substitutes for ivory and tortoise shell, celluloid became the base for a class of very valuable varnishes. It made amateur photography possible by the substitution of sensitized celluloid films for the breakable and heavy glass plates, and it provided humanity with its greatest agent of amusement and instruction—the moving picture show. But as the lesser nitrated cotton substances in celluloid, like all nitro derivatives, were not yet absolutely free from explosive risk under certain conditions, persistent efforts were made to find safe substitutes for them. Lately these experiments were carried to a successful termination, and acetylcellulose obtained by the action of acetic acid on cotton has replaced the dangerous nitro products, especially in the manufacture of non-inflammable films for moving pictures—a material in which the absence of danger from fire is obviously of the highest importance.

This acetylcellulose is also of distinct value in the manufacture of a varnish which finds its largest application in the construction of flying machines where its particular properties are of signal service. What a brilliant record of achievement in the search of militarism for a new explosive!

Militarism has also solved the problem for the textile industry as to which colors are most conspicuous and which least visible. Exhaustive tests showed that uniforms of a peculiar grayish-green shade rendered the soldier practically invisible in the field. How correct these observations were, was demonstrated at the start of the war when it was reported that the presence of the German troops was not noticed by the enemy at distances greater than two hundred to two hundred and fifty yards.

The most conspicuous color in all kinds of light was found to be red on white or white on red. This fact was made use of by the German advertising men who now paint their posters, etc., mostly in red and white, and also by the municipalities of German cities which are using