The Physiomedical Dispensatory by William Cook, M.D., 1869
Preparation: This acid may be made from tannic acid, by securing an interchange of one equivalent of oxygen for one equivalent of carbon in the latter. The simplest method of preparing it in quantity, is to mix powdered nut-galls into a thin paste with water, and expose the mixture to the air in a warm situation for two or three monthsadding water from time to time to replace that lost by evaporation. The moldy mass is then pressed strongly in a cloth, the solid residue boiled in a considerable quantity of water, and the solution filtered. The tannic acid in galls is oxidized, and thus converted into gallic acid; the boiling water dissolves this; and as cold water will not dissolve it well, the crystals of gallic acid are deposited as the solution cools. These crystals are small, feathery , nearly colorless, and silky. Its purification is effected by filtering its hot solution through a bed of animal charcoal free from all trace of sesquioxide of iron. It is feebly soluble in alcohol; soluble in one hundred parts of cold and three of boiling water; sparingly soluble in ether.
Properties and Uses: This acid is a very pure and efficient astringent; and as it does not precipitate gelatin, it thereby possesses a decided advantage over tannin for internal use, as it may reach remote vessels effectually, and is not liable to cause so much constipation. It is employed locally in all hemorrhages that can be reached by its powder or solution; and internally it is given for hemorrhages of the stomach, lungs, bladder, and kidneys. It enjoys some reputation in menorrhagia, and is undoubtedly good in chronic mucous discharges from the bladder and bowels. It may be made into an ointment for piles. Dose, internally, from five to fifteen grains, three or more times a day. It may be given in pill or powder.
Medical Herbalism journal and medherb.com