“ With ferric salts its solution gives a deep blue colour, and with ferrous salts, after exposure to the air, an insoluble, blue-black, ferroso-ferric gallate. Bases of the alkali metals give with it four series of salts; these are stable except in alkaline solutions, in which they absorb oxygen and turn brown. ”

“ With phosphorus oxychloride at 120° C. gallic acid yields tannic acid, and with concentrated sulphuric acid at 100°, rufigallic acid, C14H8O8, an anthracene derivative. Oxidizing agents, such as arsenic acid, convert it into ellagic acid, C14H8O9 + H2O, probably a fluorene derivative, a substance which occurs in gall-nuts, in the external membrane of the episperm of the walnut, and probably in many plants, and composes the “bezoar stones” found in the intestines of Persian wild goats. Medicinally, gallic acid has been, and is still, largely used as an astringent, styptic and haemostatic. ”