When a primary amine of the fatty series is acted upon by nitrous acid (HNO,), the NH, group of the amine is replaced by OH, with the formation of an alcohol; but when nitrous acid acts upon aromatic amines, the products are quite different and are known as adiazo-compounds.° Thus when nitrous acid acts upon aniline nitrate, a compound having the formula C,H.N.NO,, and known as nitrate,° is formed. This is regarded by chemists as a compound of the univalent radical GH,--N = N—. When the free affinity of this radical is saturated by the addition of phenyl (GIL) the resulting com pound, C.H.N.C.H., is icnown as “azoben ZCfle,* or as abenzene-azo-benzene.° Azo benzene may be prepared by heating nitro benzene with a solution of Sna, in aqueous caustic soda. It is deposited from a solution in benzene in the form of bright red trimetric plates and owes its importance largely to the fact that aniline yellow, GH.N.C,H4(NH,), is one of its derivatives.
Benzene is an exceedingly inflammable substance, burning with a luminous flame and the generation of a great amount of heat. It is volatile and its vapor forms a dangerously explosive mixture with air when present in any considerable quantity. Hofmann, men
tioned above as having first demonstrated its existence in coal tar, lost his life on 25 Feb. 1855, while experimenting with a considerable quantity of benzene, through the mass acci dentally taking fire. Benzene may be formed synthetically by heating acetylene gas (C,H,) to dull redness in a glass tube. Polymeriza tion occurs and among numerous other sub stances benzene is formed in accordance with the equation 3C,H2—C,Ho. In works on chemistry, benzene is often called thenzol.° (Compare BENZINE).
This product is so widely employed in the industry of the aniline dyes that chronic poi soning is by no means uncommon. It is usually breathed as vapor in the vat rooms and causes, after some exposure, dizziness in the head, ringing in the ears, nausea and vomit ing, coughing and sleepiness which latter may deepen to unconsciousness somewhat resem bling the narcosis caused by breathing chloro form. In some instances there are blood changes. with cyanosis and death. Treatment by fresh air, oxygen, free diuresis, catharsis and diaphoresis, and if the blood changes are marked infusion of physiological salt solution may be necessary.