IV.—Picric Acid and Picrates.
§ 596. Picric Acid, C6H3N3O7, or
is trinitrophenol; it forms a number of salts, all of which are more or less poisonous. Picric acid is much used in the arts, especially as a dye. The pure substance is in the form of pale yellow crystals, not very soluble in cold water, but readily soluble in hot water, and readily soluble in benzene, ether, and petroleum ether. The solution is yellow, tastes bitter, and dyes animal fibres, such as wool; but it can be washed out of plant fibres such as cotton.
§ 597. Effects of Picric Acid.—Picric acid and its salts have a tendency to decompose the elements of the blood, and to produce methæmoglobin; picric acid is also an excitor of the nervous system, producing convulsions. To these two effects must be added a third; in acid solution it has a strong affinity for albumin, so that if it meets with an acid tissue it combines with the tissue, and in this way local necroses are set up. The action on albumin is somewhat weakened by the reduction in the body of part of the picric acid to picraminic acid C6H2(NO2)2NH2OH, a substance that does not so readily form compounds with albuminous matters. Doses of 0·5 to 0·9 grm. (about 8 to 14 grains) may be taken several days in succession without marked symptoms. Ultimately, however, what is known as “picric jaundice” appears, the conjunctiva and the whole skin being stained more or less yellow. The urine, at first of a dark yellow, is later of a red brown colour. Dyspepsia, with flatulence and an inclination to diarrhœa have been noticed. A single dose of a gramme (15·4 grains) caused in a case described by Adler[614] pain in the stomach, headache, weakness, diarrhœa, vomiting of yellow matters, quickening and afterwards slowing of the pulse; the skin was of a brown yellow colour, and there were nervous symptoms. The urine was ruby red. In both fæces and urine picric acid could be recognised. The excretion of picric acid continued for six days. A microscopical examination of the blood showed a diminution of the red blood corpuscles, an increase in the white. Chéron[615] has described a case in which the application of 0·45 grm. (6·9 grains) to the vagina produced yellowness of the skin in an hour, and the urine was also coloured red. Erythema, somnolence, burning and smarting in the stomach and in the kidneys were also noticed.
[614] Wiener. med. Woch., 1880, 819.
[615] J. Chéron, Journ. de Thêr., 1880, 121.