of synthetic medicinals, dyes, perfumes, flavors, photographic articles, resins, and tanning materials.

The relation between picric acid and the dye known as sulphur black illustrates the close relationship that exists at many points between the dye industry and the high-explosives industry. Both picric acid and sulphur black are derived from benzol. The first four chemical steps in making these products are identical, yielding dinitrophenol which may then be converted into picric acid by treatment with nitric acid or into sulphur black by treatment with sulphur and sodium sulphide. steps are as follows:

This helps to make clear what is meant when it is said that the development of the dye industry is a measure of military preparedness. Some of its machinery may be turned immediately to the production of explosives, and its technical staff as well as its general equipment can be used, with comparatively little change, in the production of high explosives. Unquestionably, this was an important motive in inducing the German Government to interest itself in the strong dye industry of Germany.

Airplane production has not been without its effect on the chemical industry. In the early days of the war, airplane wings were varnished with cellulose nitrate, which ignites with ease and burns with almost explosive speed, a property which has brought sudden and fiery death to many aviators. America, however, initiated the practice of varnishing with a non-inflammable "dope" known as cellulose acetate.o This has led to a rapid increase in the output of acetic acid and acetone. Acetone has three important uses in warfare. It was one of the articles, therefore, of which there was an acute shortage. It is used in the manufacture of "cordite," the propellant of British naval shells, as a solvent for airplane wing varnishes, and in the manufacture of some substances used in gas warfare. Before the war the only source of acetone was from the distillation of wood, but the supplies were entirely inadequate to meet the war demands. The wood-distillation industry itself has been stimulated, but new sources of supply have been needed. At least four new technical processes for the manufacture of acetone have been developed and put 9 For a description of the development of this material see, in this series, Arthur Sweetser, The American Air Service.

into commercial operation since the outbreak of the European War.

Probably the largest output of acetone has been secured from molasses. The molasses is fermented to alcohol, and this in turn by a second fermentation process is converted into acetic acid. The acetic acid is then converted into lime salt, and this in turn into acetone by heating to a dull red heat. Another process has been developed for its production directly by fermentation from starchy material. The process yields a by-product of butyl alcohol in large amounts, and butyl alcohol is thus made commercially available for the first time. A third process makes acetone from calcium carbide at large plants which have been erected for the purpose at Shawinigan Falls, Canada.

The Hercules Powder Company was offered a contract for cordite by the British Government at a very profitable figure on the condition that the acetone necessary for its manufacture should be obtained from an entirely new source. By these terms the Hercules Company could not become a competitive bidder with the British Government for the existing supplies of acetone. The Hercules Powder Company developed a process for making acetone from the giant kelp, a submarine tree which grows off the California coast.

It is not yet clear whether any of these processes will continue in operation when the war demand for acetone disappears. Their success will depend partly, at any rate, on the market for and the tariffs on their byproducts. Some of them may be a permanent factor in the acetic-acid industry, even if they cannot make acetone in competition with the wood-distillation process. The factory using kelp has already been closed.

The histories of antimony and mercury are interesting

in their relation to the war. During the four-year period 1913-16 the price of antimony fluctuated from 7.5 to 30.2 cents per pound, and that of mercury from $39.54 to $125.49 per flask of 75 pounds. Antimony is used in warfare chiefly for hardening lead for shrapnel bullets, and also, in the form of the sulphide, as an ingredient of some primers and as an addition to the explosive content of shells for making a smoke which will assist gunners in finding their range. Mercury's most important use is in the form of fulminate of mercury for detonators of big shells and cartridges. The war demands and shipping restrictions have brought about radical changes in the antimony and mercury industries.

Over half the world's antimony is mined in China. Other producers are France, the United States, Algeria, and Mexico. For many years before the war the available supplies of antimony ore far exceeded the world demand, and there was little to encourage development of antimony deposits other than those from which highgrade ores could be obtained. After the outbreak of the war there was a curtailment of the metal; Chinese and South American antimony became difficult to move on account of shipping shortage, and Mexican supplies were unstable. In these circumstances considerable activity resulted, and many deposits in the United States which had remained idle for a long period were again put in operation.

During 1904 and 1905 the United States led the world. in the production of mercury, but since 1906 Spain has been the leading producer, and has accounted for about one-third of the total. Italy, Austria, and the United States have made up the major part of the remaining two-thirds, in proportions varying only slightly in the order named. On the outbreak of the war Austrian

supplies were at once cut off, and Spanish supplies, controlled mainly in London, were held for Allied use. Spanish and Italian production has been largely increased since 1914, and the industry in the United States has also undergone wide expansion. The rich ores in the United States are practically exhausted and few mines have large reserves of even low-grade ore. Treatment of material carrying less than 0.25 per cent. mercury is not unusual in the United States, whereas the Spanish mines at Alamaden have been treating in recent years ore averaging 11 per cent. mercury. The decreasing grade of American ore has resulted in a steady fall in the production per furnace which has not been met by the construction of additional equipment.

Many other important developments in the chemical industries might be mentioned. Incendiary bombs, smoke screens at sea, star shells, signal rockets, and other war demands have stimulated the production of important chemicals. Sufficient has been said, however, to indicate the profound effect that the war has had, both directly and indirectly, upon the chemical industries. Many plants have been erected with the express understanding that they were to be scrapped when peace came. Ample allowance has been made for amortization, but the problem is not so simple as that. The building of plants, the training of skilled labor, the complex inter-relationship of industries, and especially the problems of national defense present a task of readjustment which requires all the constructive genius of our business men and statesmen. Even the hasty review here given of the effect of the war on the chemical industries should make clear their vital importance in the industrial and military activities of the American people.