CLASSIFICATION AND APPLICATION OF DYES Vegetable dyes were the first hair dyes, then metals, and finally the synthetic organic dyes. First, we have the organic vegetable colorings which are best represented by henna, indigo, wood extracts (logwood, redwood, pyrogallol and tannin) and herbs such as sage and camomile. Second, metallic preparations, such as silver, lead, copper, cobalt, tin, bismuth, cadmium, nickel and iron. Third, compound dyestuffs utilizing mordants, which are a mixture of a vegetable dye such as henna with a metallic preparation such as copper or iron. Fourth, aniline derivatives and other synthetic organic compounds. 1. Vegetable Compounds.— Henna, the best known example of this group, is a small plant which grows chiefly in Morocco, Algiers, Tunis, Egypt, Arabia and India. The method of using henna dye has always been the same. The dried leaves and stems are ground to a powder and made into a thick paste with