Dinitrobenzene

DINITROBENZENE, C₆H₄(NO₂)₂, is obtained from benzene by treatment with nitric acid (or a mixture of nitric and sulfuric acids) at an elevated temperature; colorless needles. It melts at 91°, dissolves poorly in water, well in alcohol, and possesses the odor of nitrobenzene (bitter almonds). Dinitrobenzene serves as a starting material in the chemical industry; with ammonium nitrate and trinitronaphthalene, it forms roburite, a very common explosive substance. Dinitrobenzene is one of the most dangerous industrial poisons of the aromatic group. In its toxic properties, dinitrobenzene resembles nitrobenzene; it penetrates the organism through intact skin, causes the formation of methemoglobin, and dissolves blood corpuscles; the symptoms of poisoning are also similar, but the clinical picture of dinitrobenzene poisoning is more severe. The greatest number of occupational poisonings by dinitrobenzene was observed in the military industry of England and Germany during the war years. Here, along with acute cases, numerous subacute and chronic poisonings were encountered with severe anemia, a yellowish-gray skin coloration, and cyanosis; in more severe cases, the central nervous system (convulsions, loss of consciousness, coma) and the organs of vision and hearing were affected; acute yellow atrophy of the liver was also observed (in Germany, 113 cases with a fatal outcome). In other respects (predisposition, course, treatment, prophylaxis), see Nitrobenzene. The objects of investigation in occupational poisonings are the urine of poisoned individuals (a portion of the dinitrobenzene passes into the urine unchanged) and the air of work premises. The urine under investigation, after acidification with dilute sulfuric acid, is repeatedly extracted with ether. The ether extract is evaporated at room temperature. The residue is treated with acetone. The solution in a measuring flask (25-50 cm³) is diluted with acetone to the mark. To a portion of the solution, 1-5 drops of a 5% solution of sodium hydroxide are added: a blue-violet coloration appears (the color is unstable). For colorimetric determination, to equal volumes of the acetone solution under investigation and standard solutions containing hundredths of a milligram of meta-dinitrobenzene (prepared by diluting an acetone solution from a specific weight of the pure preparation), 0.2-0.4 cm³ of a 5% sodium hydroxide solution are added from burettes, and after 15-20 minutes, the coloration is compared. When determining in air, a known volume of the latter is drawn with the help of an aspirator (see Industrial poisons—isolation) through 2-3 wash bottles with acetone. The liquids from the wash bottles are poured into a measuring flask, brought to the mark, and the amount of dinitrobenzene is determined colorimetrically, as described above.