Definition. - A diatomic phenol [metadihydroxybenzene, C6H4(OH)2 1:3] obtained usually by the reaction of fused sodium hydroxide upon sodium metabenzene-disulphonate.

Origin. - Prepared by melting galbanum, ammoniac, or guaiacum resin with potassa. It is also prepared in a similar manner from nsafetida, sagapenum, ascaroid resin, and from phenolsulphonic acid and other derivatives from phenol.

Description and Properties. - Colorless or faintly reddish, needle-shaped crystals, or rhombic plates, having a faint, peculiar odor, and a disagreeable sweetish and afterward pungent taste. Resorcinol acquires a pinkish or brownish tint by exposure to light and air, and should be kept in dark amber-colored vials. It is soluble in 0.5 part of water, more in alcohol, very soluble in boiling water and in boiling alcohol, readily soluble in ether and in glycerin, and very slightly soluble in chloroform. The aqueous solution is neutral or only faintly acid to litmus-paper.

Dose. - 3-8 grains (0.2-0.5 Gm.) [2 grains-.I25 Gm., U. S. P.].