A body obtained from gallic or tannic acid by carefully heating.

Characters.-Very small shining colourless crystals, becoming black on exposure; odourless, insipid; not acid to test-paper; readily soluble in water.

Dose.-1/2 to 1 1/2 gr.

Action And Uses

Pyrogallic acid has a powerful affinity for oxygen, and is thus antiseptic and disinfectant (in 1 to 2 1/2 per cent. solutions). It stains the skin and hair dark without injuring their structure. It also acts as a powerful but somewhat painful local stimulant, which will destroy excessive cutaneous growths, and may be used (60 gr. to one ounce of lard) in psoriasis, but only when the patches of disease are small, in lupus, and in epithelial cancer.

Whether applied freely to the skin, or given internally in large doses, pyrogallic acid has a destructive influence on the blood, which assumes a brown "fluid" appearance and readily coagulates, the corpuscles being the elements affected. Vomiting, purging, bloody urine, great nervous and general depression, are the results of this blood change, which may prove fatal; hence the caution given in the last paragraph. The drug has been used in haemoptysis.