ROSIN (a later variant of "resin," q.v.) or Colophony (Colophonia resina, resin from Colophon in Lydia), 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 copper stills. The essential oil is carried off at a heat of between 212° and 316° F., leaving fluid rosin, which is run off through a tap at the bottom of the still, and purified by passing through a straining wadding. Rosin 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 pale, - superior 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 piny odour; the melting-point varies with different specimens, some being semi-fluid at the temperature of boiling water, while others do not melt till 220 or 250° F. It is soluble in alcohol, ether, benzene and chloroform. Rosin consists mainly of abietic acid, and combines with caustic alkalis to form salts (rosinates or pinates) that are known as "rosin soaps." In addition to its extensive use in soap-making, rosin is largely employed in making inferior varnishes, sealing-wax and various cements. It is also used for preparing shoemaker's wax, as a flux for soldering metals, for pitching lager beer casks, for rosining the bows of musical instruments and numerous minor purposes. In pharmacy it forms an ingredient in several plasters and ointments. On a large scale it is treated by destructive distillation for the production of rosin spirit, pinoline and rosin oil. The last enters into the composition of some of the solid lubricating greases, and is also used as an adulterant of other oils.
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.
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