1902 Encyclopedia > Rosin

Rosin




ROSIN, or COLOPHONY, is the resinous constituent of the oleo-resin exuded by various species of pine, known in commerce as crude turpentine (see TURPENTLNE). 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°, leaving fluid rosin, which is run off through a tap at the bottom of the still, purified by passing through a straining wadding, and received into a vat, whence it is ladled into barrels ready for the market. 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 very brittle and friable resin, with a faint piny odour, softening at about 176° and melting completely at the temperature of boiling water. It dis-solves freely in ether, benzol, and chloroform, and to some extent in alcohol and fatty oils. When exposed to the action of hot dilute alcohol or when boiled with alkaline solutions it takes up a molecule of water and becomes converted into abietic acid, a change which also takes place slowly in the air when the resin is yet mixed with the essential oil as it flows from the trees. Rosin is thus regarded as an anhydride of abietic acid, and its use in yellow soaps is due to the fact that this acid itself com-bines with caustic alkalies to form a kind of soap. 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, 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 an oily complex hydrocarbon, having a tarry odour and a. whitish opalescent colour, which under the name of rosin oil is much used as a lubricant. Rosin oil also enters extensively into the common kinds of fatty oils as an adulterant.

The chief re,c,rion of rosin production is the southern coast States of the American Union, - the ports of 'Wilmington, Charleston, Savannah, and Bninswick being the principal centres of the trade. American rosin is obtained from the turpentine of the swamp pine, RIMS australis, and of the loblolly pine, P. Terda. The main source of supply in Europe is the." landes " of the depattmentsof Gironde and Landes in France, where the sea pine, P. maritima, 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. The imports iuto the -United Kingdom average about 1,250,000 cwts. annually, nearly the whole of which comes from America. In 1883 the amount imported was 1,377,368 cwts. (1,337,848 cwts. from the United States and 16,242 cwts. from France), the total esthnated valne of the imports being £400,938.








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