Resin soaps are compounds of soda or potash with the complex acids (chiefly abietic) of which coniferous resins consist.
Examples of resin acids are abietic (sylvic) acid, C19H2802, occurring in colophony, and pimaric acid, C20H3002, a constituent of gallipo resin.
Abietic acid can be extracted from colophony by means of hot alcohol; it crystallizes in leaflets, and on oxidation yields trimellitic, isophthalic and terebic acid.
Pimaric acid closely resembles abietic acid into which it passes when distilled in a vacuum; it has been supposed to consist of three isomers.
Rosin consists mainly of abietic acid, and combines with caustic alkalis to form salts (rosinates or pinates) that are known as "rosin soaps."
