ROSIN or COLOPHONY, the resinous constituent of the oleo-resin exuded by various species of pine, known in commerce as crude turpentine. The separation of the oleo-resin into the essential oil-spirit of turpentine and common rosin is effected by distillation in large stills. Rosin (a later variant of "resin," q.v.), varies in colour, according to the age of the tree whence the turpentine is drawn and the amount of heat applied in distillation, from an opaque almost pitchy black substance through grades of brown and yellow to an almost perfectly transparent colourless glassy mass. The commercial grades are numerous, ranging by letters from A. the darkest. to N. extra Dale.—sunerior to which are W, "window glass," and WW, "water white" varieties, the latter having about three times the value of the common qualities. Rosin is a brittle and friable resin, with a faint pine-like odour; the melting-point varies with different specimens, some being semi-fluid at the temperature of boiling water, while others do not melt till 22o° or 25o° F. It is soluble in alcohol, ether, ben zene and chloroform. In addition to its extensive use in soap
making, rosin is largely employed in making inferior varnishes, sealing-wax, various cements and as a sizing agent in the manu facture of paper. It is also used for preparing shoemakers' wax, as a flux for soldering metals, for pitching lager beer casks, for rosining the bows of musical instruments, etc. In pharmacy it forms an ingredient in several plasters and ointments.
The chief region of rosin production is the South Atlantic and Eastern Gulf states of the United States. American rosin is obtained from the turpentine of the swamp pine, Pinus australis, and of the loblolly pine, P. Taeda. The main source of supply in Europe is the "landes" of the departments of Gironde and Landes in France, where the cluster pine, P. Pinaster, is extensively cultivated. In the north of Europe rosin is obtained from the Scotch fir, P. sylvestris, and throughout European countries local supplies are obtained from other species of pine.