An organic acid, HC14H908, obtained from nutgall.

Properties : Tannic acid occurs as a light yellowish, amorphous powder, gradually turning darker when exposed to air and light. It has a faint, characteristic odor and a strongly astringent taste. Tannic acid is very soluble in water, alcohol and glycerin.

Incompatibilities: It is incompatible with   alkalies, alkaloids, salts of iron and of most other metals,  albumin and gelatin. With all these substances it reacts  to form insoluble compounds.

Action and Uses: Tannic acid is used as an astringent and hemostatic. Internally it has been chiefly employed in the treatment of diarrhea. It is but little used with infants or children. It should be employed not as the principal curative agent, but as an occasional adjunct to proper dietetic and physical remedies when the discharges are unduly profuse. Its astringent action, however, often causes nausea and vomiting, and hence some one of the protein combinations is better for action on the intestine. Local applications of tannic acid are frequently made to inflamed mucous membranes, especially in pharyngitis. It is frequently employed as a local application in the treatment of hemorrhoids in the form of a 20 per cent. ointment or as a suppository containing 0.3 gm. or 5 grains. Dosage: 0.3 gm. or 5 grains.