The true pitch is very extensively replaced by an artificial compound, termed poix blanch,e in Belgium, and poix blanche factice in France. It is composed either of galipot melted in water, stirred, and filtered hot, or of a mixture of galipot (thus) or colophony with turpentine, turpentine oil, or Bordeaux turpentine, coloured with palm-oil. The artificial article differs from the genuine in being completely soluble in alcohol, less tenacious and adherent, and of stronger and less fragrant odour.
Quebracho.—The so-called " gum " of Quebracho colorado is in reality an astringent extract, and will be described under Tannin.
Retinite.—This name was applied some years since to a species of fossil resin, found in small nodules and masses, sometimes in imperfect veins, in the brown coal and gold diggings at Caversham, Tarapeton, Waitahuna, and other parts of Otago (New Zealand); also in Borneo. It melts without decomposition, emitting an aromatic odour, and burns with a smoky flame ; warmed gently with alcohol, it softens, and becomes very tenacious and adhesive. The sp. gr. is about 1.049. The colour varies from pale-yellow to dark-brown.
Rimu.—The rimu or Dacrydium cupressinum of New Zealand yields an exudation which can be converted into a varnish in no way inferior to copal.
Rosin or Colophony (Fs., Colophane, Brai, Arcanson; GER., Colophonium, Geigenharz, Gemeines Harz) and Rosin-oil.—The several kinds of rosin, colophony, or resin proper are the solid residues obtained by the distillation of the turpentines (see pp. 1686-92). The crude turpentine or oleo-resin is submitted to aqueous distillation in a copper vessel, in place of the old-fashioned iron still which produced a red-coloured oil. The still, having a capacity of some 15 barrels (of 220 Ih. each), is charged with crude oleo-resin in the early morning ; heat is applied either by an ordinary furnace, or by a steam-jacket, until the mass attains a uniform temperature of 100°-158° (212°-316° F.). This is continued until the accidental water contained in the crude oleo-resin has been driven off, together with pyroligneous and formic acids, ether, and methylic alcohol, the whole being known as " IONV wine." This accomplished, a small stream of cold water is admitted, so that the heat is kept at or below 158° (316° F.), the boiling-point of turpcntine-oil. The distillation continues, a mixture of water and turpentine-oil passing over into a wooden separating tub ; this is merely a tub with two outlet taps, one near the bottom, the other about half-way from the top, the difference in sp. gr. of the two bodies permitting their withdrawal into separate receptacles. The progress of the distillation is judged by means of samples taken at intervals in a, graduated measure ; \\hen the liquid shows 9 parts of vvater to 1 of turpentine-oil, the dihtillation is stopped, the still-cap is removed, and the hot rosin remaining in a fluid condition in the still is drawn off by a tap near the bottom, and passed through a fine strainer iuto a vat, whence it is baled by long handled wooden buckets into barrels for sale.
The grade of the rosin depends (1) upon tlie quality of the crude oleo-resin under treatment, and (2) upon the skill with which the operation is conducted. The so-called " virgin turpentine," the first exudation from a newly-chipped tree, will give " window-glass " rosin of varying quality ; " yellow dip," the runnings of the second and subsequent years, affords medium grades of rosin ; while " scrapings," the inspissated gum from the tree facings (see Thus, p. 1684), yields an inferior dark rosin. Black rosin is not caused by burning iu the still, as has been stated. Opacity is due to the presence of water, by which, crystals of abietic acid are formed. Every turpentine produces its own peculiar rosin. That most common iu continental Europe is obtained from Bordeaux turpentine (sec p. 1687); in England aud America, that derived from the latter country holds the foremost place. Speaking in general terms, rosin is au almost flavourless body, of faint but characteristic odour, and varying in colour from the palest amber to the deepest black, and from tranhlucent to opaque. Common yellow rosin is homogeneous, amorphous, very friable, and of sp. gr. 1.07 ; it softens at 80° (176° F.), and fuses coinpletely to a limpid yellow liquid at 100° (212° F.). It is insoluble iu water, but soluble in acetone and benzol in nearly all proportions, in 8 parts of alcohol of 88° at 15°-20° (59°-68° F.), and pretty freely in ether and fatty oils. Treated with boiling alkaline solutions, it takes up the elements of water to form abietic acid, which then unites with the alkali present to form rosin-soap (see Soap). The rosin of Venice turpentine (see p. 1691) dissolves in 2 parts of hot alcohol of 75°. That of Canadian turpentine (see p. 1686) consists of two ingredients, one (78'7 per cent.) soluble in boiling absolute alcohol and glacial acetic acid, and the other (21.3 per cent.) soluble in ether ; both the turpentine and the rosin are insoluble in caustic alkalies. The rosin of Strassburg turpentine (sce p. 1691) is completely soluble in glaoial acetic acid, but incompletely in acetoue and absolute alcohol. Medicinally, rosin is employed in plaisters; industrially, in the rnauufacture of rosin-soap, sealing-wax, varnishes, and cements, and for soldering metals. The approximate London ruarket value is 5-15i. a cwt.