or Rosin, is the name commonly applied in commerce to the colophony, or solid residuum, obtained by distilling common turpentine, which consists of from 10 to 25 per cent. of the essential oil called spirit of turpentine, and the remainder of the brittle, brown transparent rosin, the composition of which is of a complicated nature, the following products being all obtained from this substance:—Terebene, colophene, resinene, retinaptha or tolone, retinyle or cumole, retinole, naphthalin, metamaphalin, besides others less known. All these substances are combinations in different proportions of hydrogen and carbon, and are called chemically hydro-carbons. Of late a valuable compound, resembling in most respects a vegetable oil, has been manufactured from rosin, and is now extensively manufactured both in Europe and America. It is about the colour of rape-oil, and is largely used in adulterating the common vegetable oils.

This rosin-oil is a combination of the retinaptha C₁₄H₈ retinyle C₁₀H₁₅ retinole C₉H₁₆ and the metamaphalin C₉H₁₆ and is separated from the other constituents by distillation. Several attempts have been made from time to time to use the gas which is formed by the decomposition of rosin-oil in the place of the coal-gas in ordinary use. The most extensive attempt of the kind was made at Southport in Lancashire, which formerly was lighted with rosin gas. The expense of its production in a neighbourhood where coal is plentiful has, however, led to its use being abandoned. Rosin is completely soluble in alkaline leys, and is consequently available in the manufacture of the commoner kinds of soap, and is for this purpose very extensively employed. It is also used for a variety of purposes in the arts and manufactures, and in the composition of various pharmaceutical preparations, such as plasters and ointments, but is employed internally only in horse medicines.

Many plants of the nat. ord. Coniferae yield turpentine and rosin abundantly; but so plentiful is the supply yielded by two species (Pinus Taeda, Lambert, and P. palustris, Lambert), which are amongst the commonest forest trees of the United States, that nearly all the turpentine used in this country is imported from America. The quantity received in the various ports of this kingdom in 1858 was 12,043 tons. It is imported in barrels, each containing about 2½ cwt., and is in colour and consistency much like honey.

There are other resins besides that procured from turpentine: they are usually termed gums or gum-resins. The following are the best known and most useful:

Copal—Which is supposed to be yielded by some species of the genus Hymenaea, large tropical trees of the nat. ord. Leguminosae. There are two kinds in commerce,—the Indian, which is received from Bombay in irregular-shaped fragments of a straw colour, and transparent when in thin pieces; the other is from Sierra Leone and other ports of Western Africa. This kind is in much larger lumps, varying in size from a hen's egg to that of a man's fist, and is imported in very large quantities. It is less valuable than the Indian variety, being coarser and less translucent: both are used exclusively in the manufacture of varnishes. There is a Brazilian species, but it is not well known. Mastic is the produce of Pistacia lentiscus (Linn.) It is brought chiefly from Mogadore and other North African ports. Two kinds occur in commerce; the better sort is in small roundish tears of a yellowish colour, slightly translucent. It is picked from the mastic bushes. The other sort is in irregular masses which have fallen from the branches to the earth, and are consequently mixed with many impurities. Both are used in the manufacture of the fine varnish used for varnishing prints, maps, and drawings.

Several other resins are used in small quantities in medicines, but are not of much importance. The imports of gum-resins in 1858 were:—Copal (also called gum antil) 8900 cwt.; mastic, 1100 cwt.; olibanum, 120 cwt.; asafoetida, 1316 cwt.; guaiacum, 73 cwt.; benzoin, 104 cwt.; ammoniacum, 126 cwt.; ephorbium, 27 cwt. The less known ones were entered as gums unenumerated consequently their separate quantities are unknown. (T.C.A.)