WOMEN IN A MUNITION PLANT ENGAGED IN THE MANUFACTURE OF TRI-NITRO-TOLUOL, THE MOST IMPORTANT OF MODERN HIGH EXPLOSIVES] The active agent in all these explosives is the nitrogen atom in combination with two oxygen atoms, which the chemist calls the "nitro group" and which he represents by NO_{2}. This group was, as I have said, originally used in the form of saltpeter or potassium nitrate, but since the chemist did not want the potassium part of it--for it fouled his guns--he took the nitro group out of the nitrate by means of sulfuric acid and by the same means hooked it on to some compound of carbon and hydrogen that would burn without leaving any residue, and give nothing but gases. One of the simplest of these hydrocarbon derivatives is glycerin, the same as you use for sunburn. This mixed with nitric and sulfuric acids gives nitroglycerin, an easy thing to make, though I should not advise anybody to try making it unless he has his life insured. But nitroglycerin is uncertain stuff to keep and being a liquid is awkward to handle. So it was mixed with sawdust or porous earth or something else that would soak it up. This molded into sticks is our ordinary dynamite. If instead of glycerin we take cellulose in the form of wood pulp or cotton and treat this with nitric acid in the presence of sulfuric we get nitrocellulose or guncotton, which is the chief ingredient of smokeless powder. Now guncotton looks like common cotton. It is too light and loose to pack well into a gun. So it is dissolved with ether and alcohol or acetone to make a plastic mass that can be molded into rods and cut into grains of suitable shape and size to burn at the proper speed. Here, then, we have a liquid explosive, nitroglycerin, that has to be soaked up in some porous solid, and a porous solid, guncotton, that has to soak up some liquid. Why not solve both difficulties together by dissolving the guncotton in the nitroglycerin and so get a double explosive? This is a simple idea. Any of us can see the sense of it--once it is suggested to us. But Alfred Nobel, the Swedish chemist, who thought it out first in 1878, made millions out of it. Then, apparently alarmed at the possible consequences of his invention, he bequeathed the fortune he had made by it to found international prizes for medical, chemical and physical discoveries, idealistic literature and the promotion of peace. But his posthumous efforts for the advancement of civilization and the abolition of war did not amount to much and his high explosives were later employed to blow into pieces the doctors, chemists, authors and pacifists he wished to reward. Nobel's invention, "cordite," is composed of nitroglycerin and nitrocellulose with a little mineral jelly or vaseline. Besides cordite and similar mixtures of nitroglycerin and nitrocellulose there are two other classes of high explosives in common use.