b-Naphthol condensed with hydrochloric acid and formaldehyde yields a methylenedinaphthol, which is insoluble in water; the sodium salt, however, easily dissolves. The same condensation, however, takes place in alkaline solution with direct formation of the sodium salt. The condensation product gives a slight precipitate with gelatine, and a bluish-grey precipitate with ferric chloride; acids re-precipitate the insoluble methylene compound. Towards pelt it exhibits tanning properties, whereby the insoluble product referred to above is deposited, and soft, full, and white leather is obtained, possessing, however, but little tensile strength. 4. Condensation of the Anthracene Group Anthracene heated with excess sulphuric acid yields the water-soluble anthracenesulphonic acid; the latter, when heated with formaldehyde, yields water-soluble, reddish-brown condensation products, which remain soluble on prolonged heating with formaldehyde. The aqueous solution of the condensation product shows no particular reactions; it gives a flocculent precipitate with gelatine and a green precipitate with copper sulphate, soluble with blue colour in excess of the reagent. The partly neutralised solution tans pelt--to which it imparts a brown colour--in eight days, but on the surface only; the inner layers are merely pseudo-tanned (white colour). When dried, pelt thus treated yields a full and soft leather with brown grain and flesh possessing but little tensile strength. Hence, this condensation product exerts a pickling rather than a tanning effect. Anthraquinone heated with sulphuric acid and treated with formaldehyde in the usual manner, yields a substance which, when mixed with water, forms an opaque, milky solution. This is not altered by excess of caustic soda. The aqueous solution precipitates gelatine and aniline hydrochloride; all other tannin reagents give no reaction. The partly neutralised solution of the condensation product exerts, in the main, a pickling action on pelt; only the surface of which is tanned, with brown colour, the remainder being merely pickled (white colour). During "tannage," bakelite is formed in the liquid, and practically all solubles originally present are deposited. The tannage completed, a light brown, fairly soft and full leather, possessing little tensile strength, results; this leather can be washed only with great difficulty and approaches more the character of a pickled pelt. 1-Hydroxyanthraquinone, 1,5-dichloroanthraquinone, l,5-diaminoanthraquinone, 1-methylaminoanthraquinone, 1-benzoylamino, 6-chloranthraquinone, 1-_m_-toluidoanthraquinone, when treated with sulphuric acid and formaldehyde, all yield condensation products which are but little soluble in water, and which do not at all precipitate gelatine. Tanning experiments with these condensation products in alcoholic solution yielded empty leathers of pronounced pickle character.