GUA′IACIN

Syn. Guaiacic acid , Pure guaiacum resin . A substance having the nature of an acid, discovered by Trommsdorff in the wood and bark of Guaiacum of ficin ale . Prep. The tincture of guaiacum is treated with hydrate of lime, and the guaiac ate of lime thus formed is decomposed with dilute sulphuric acid; it is purified by di olving it in alcohol. Prop., . Insoluble in water; soluble in alcohol and ether; it unites with the caustic alkalies, forming alkaline guaiac ates (guaiacum soaps); air and light turn it green; gluten, mucilage of gum Arabic, ., turn it blue; nitric acid and chlorine turn it succe ively green, blue, and brown; tincture of guaiac in, added to hydrocyanic acid and sulphate of copper, produces an intense blue colour. (Pagenstecher.) A delicate photographic paper may be formed by washing unsized paper with an alcoholic solution of guaiacum resin, and afterwards with one of neutral acetate of lead. (Johnston.)