The first product obtained consist in the addition of one acetylene to the arsenic trichloride molecule, and, chemically, is chlorovinyldichloroarsine, CHCl: CH·AsCl₂, a colorless or faintly yellow liquid, boiling at 93° at a pressure of 26 mm. A small quantity, even in very dilute solution, applied to the skin causes painful blistering, its virulence in this respect approaching that of mustard gas. It is more valuable than mustard gas, however, in that it is absorbed through the skin, and as stated on page 23, three drops, placed on the abdomen of a rat, will cause death in from one to three hours. It is also a very powerful respiratory irritant, the mucous membrane of the nose being attacked and violent sneezing induced. More prolonged exposure leads to severe pain in the throat and chest. The second fraction (β, β′-dichlorodivinylchloroarsine) is a product resulting from the addition of two acetylene molecules to one arsenic trichloride, and boils at 130° to 133° at 26 mm. It is much less powerful as a vesicant than chlorovinyldichloroarsine, but its irritant properties on the respiratory system are much more intense. The third fraction, β, β′, β″-trichlorotrivinylarsine, (CHCl: CH)₃As, is a colorless liquid, boiling at 151° to 155° at 28 mm., which solidifies at 3° to 4°. It is neither a strong vesicating agent nor a powerful respiratory irritant. At the same time, its odor is pungent and most unpleasant and it induces violent sneezing. CHAPTER XI CARBON MONOXIDE Carbon monoxide, because of its cheapness, accessibility and ease of manufacture, has been frequently considered as a possible war gas. Actually, it appears never to have been used intentionally for such purposes. There are several reasons for this. First, its temperature of liquefaction at atmospheric pressure is -139° C. This means too high a pressure in the bomb or shell at ordinary temperatures. Secondly, the weight of carbon monoxide is only slightly less than that of air, which keeps it from rolling into depressions, dugouts and trenches, as in the case of ordinary gases, and also permits of its rather rapid rise and dissipation into the surrounding atmosphere. A third reason is its comparatively low toxic value, which is only about one-fifth that of phosgene. However, as it can be breathed without any discomfort, and as it has some delay action, its lack of poisonous properties would not seriously militate against its use were it not for the other reasons given.