Resina. U. S., Br. Rosin.

Resin. [Resin, Colophony]

Related entries: White pine bark - Riga balsam - Oil of Turpentine - Rectified Oil of Turpentine

"The residue left after distilling the volatile oil from the concrete oleoresin obtained from Pinus palustris Miller and from other species of Pinus (Fam. Pinaceae)." U. S. "Resin is the residue left after the distillation of the oil of turpentine from the crude oleo-resin (crude turpentine) of various species of Pinus." Br.

Colophone ou Arcanson, Fr. Cod.; Resine blanche, Resine jaune, Fr.; Colophonium, P. G.; Kolophonium, Geigenharz, Fichtenharz, G.; Colofonia, Pece greca, It.; Cologonia, Pez griega, Sp.

After the distillation of the volatile oil from the turpentine (see Terebinthina), a resinous matter remains, which on the continent of Europe is called colophony, but with us is commonly and now officially known by the name of rosin. It is the Resina of the U. S. and British Pharmacopoeias. It is sometimes called resina flava, or yellow rosin. When this, in a state of fusion, is strongly agitated with water it acquires a distinct appearance, and is denominated resina alba, or white rosin. The ports from which rosin is shipped are Wilmington, N. C., Charleston, S. C;, and Savannah, Ga. The exports of rosin in 1904 amounted to 2,585,-108 bbls., valued at $6,621,870; and in 1905 to 2,310,275 bbls., valued at $7,069,084.

Common or yellow rosin, in its purest state, is beautifully clear and pellucid, but much less so as usually found in commerce. Its color is yellowish-brown with a tinge of olive, and more or less dark, according to its purity and the degree of heat to which it has been exposed in its preparation. Sometimes it is almost black. It is rather heavier than water. It is completely liquid at 152.5° C. (306° F.), begins to emit bubbles of gas at 157.5° C. (316° F.), and is decomposed at a red heat. The official description is as follows: "Rosin usually occurs in sharp, angular, translucent, amber-colored fragments, frequently covered with a yellow dust, brittle at, the ordinary temperature; fracture shiny and shallow-conchoidal; odor and taste slightly terebinthinate. It is freely soluble in alcohol, ether, benzene, glacial acetic acid, or fixed or volatile oils, it is also dissolved by dilute solutions of the fixed alkali hydroxides. Its alcoholic solution is acid to litmus. Specific gravity: 1.07 to 1.09 at 25° C. (77° F.). It is easily fusible and burns with a dense yellowish smoke. Incinerate about 2 Gm. of Rosin; not more than 0.05 per cent. of ash remains. The acid number of Rosin is not less than 150." U. S.

"Translucent, of a light amber color, compact, brittle, pulverisable; fracture shining; odor and taste faintly terebinthinate. Soluble in alcohol (90 per cent.), in ether, benzene, and carbon disulphide. Readily fusible; burns with a dense yellow flame and much smoke, leaving no appreciable ash." Br.

The composition of rosin is expressed by the formula C₄₄H₆₂O₄, which is the formula ascribed to abietic anhydride. Jean, however (Chem. News, xxvi, 207), has separated two other resinoid substances in addition to abietic acid. Lewkowitseh (Chem. Analysis of Oils, etc., 2d ed., 236) states that rosin also contains varying quantities of unsaponifiable matter—viz., hydrocarbons due to the partial breaking up of the acid on distilling the pine rosin. This may vary from 5 to 9 per cent. in the American rosin. For a paper on abietic acid by Mead and Kremers, see Proc. A. Ph. A., 1893, 198. By shaking coarsely powdered rosin with dilute alcohol and warming, it is converted into abietic acid, C₄₄H₆₄O₅. obviously an hydroxide of the first. Rosin may be considered, therefore, as abietic acid anhydride, C₄₄H₆₂O₄. Rosin, when it is boiled with alkaline solutions, forms greasy salts of abietic acid, the so-called rosin soaps which are used in admixture with other soaps. As the acid is dibasic, these salts contain two atoms of alkali metal in combination. Rosin, distilled by itself, yields the so-called "rosin-oil," of which two fractions are taken separately—the first that distilling under 360° C. (680° F.), and the second that over 360° C. (680° F.)—and some 31 per cent. of fixed gases. The lighter fraction is known commercially as rosin essence, and is, according to Renard (J. Chem. S., Aug., 1884, p. 843), composed of hydrocarbons, representing almost all series, from. the paraffin series to the terpenes, including pentane and hexane, amylene and hexylene, toluene, xylene, and cumene, the tetra- and hexa-hydrides of all three of these, terebenthene and cymene. Several aldehydes and acids of the fatty series, such as isobutyric and valeric, were also recognized. The heavier fraction, or rosin oil in the stricter sense of the word, is composed of polymers of the hydrocarbons CnH_2n-2, which readily resinify by the absorption of oxygen. This accounts for the use of rosin oil as an adulterant of linseed oil in the manufacture of printers' ink. When distilled with superheated steam, rosin yields benzene and toluene. Sylvic acid, formerly considered to be a constituent of rosin, is now regarded as a decomposition product of abietic acid. Similarly pinic and pimaric acids, announced as found in rosin, are impure products, although the latter acid, or one of the same name, is found in galipot resin. Propionic acid has, according to Renard, been obtained in abundance from the tar produced by the destructive distillation of rosin. (A. Pharm., 1886, p. 939.)

A. Tschirch and B. Studer determined the nature of the constituents of American rosin. According to Mohr, the principal plant yielding the turpentine from which the American rosin is obtained is Pinus palustris Mill.; to some extent also, P. heterophylla Ell.;rarely P. echinata, P. Taeda and P. scropida (no such plant -Henriette). The sample under examination (presumably from P. palustris) was completely soluble in the ordinary solvents for resin, including petroleum benzin, in which some other varieties of rosin are only partly soluble. Its alcoholic solution is strongly acid in reaction. Its sp. gr. at 15° C. (59° F.) was 1.090. Its composition was proved to be as follows:

1. Acids soluble in ammonium carbonate: α-abietinic acid, C₁₉H₂₈O₂, forming an insoluble lead salt, 30 per cent. β-abietinic acid, C₁₉H₂₈O₂, not forming a lead salt, 22 per cent.
2. Acid soluble in sodium carbonate: γ-abietinic acid, C₁₉H₂₈O₂, insoluble in ammonium carbonate, 31.06 per cent.
3. Volatile oil, 0.4 to 0.7 per cent.
4. Resen, 5 to 6 per cent.

The impurities amounted only to 0.1 per cent., the loss in operation, however, to 10 per cent. Fahrion having proposed a method for the differentiation of different rosins, based upon their relative solubility in petroleum benzin, the authors determined the amount of solvent necessary to dissolve 1 Gm. of rosin, freshly powdered, and old powder; also abietinic acids and the resen in petroleum benzin, with the following results:

These results show that all the resin-acids, as well as the rosin, are more or less soluble in petroleum benzin, and that fresh rosin is more readily soluble than the isolated acids, a peculiarity which has also been noticed in the case of other bodies. On the other hand, old rosin is much less soluble in petroleum benzin than is fresh rosin. (A. Pharm; Oct., 1903, 495-522.)

White rosin differs from the preceding only in being opaque and of a whitish color. These properties it owes to the water with which it is incorporated, and which gradually escapes upon exposure, leaving it more or less transparent. A new and very interesting class of derivatives from colophony or rosin has been prepared by Eugen Schaal, of Feuerbach, Germany, and introduced into commerce under the name of ester gums. These are the glyceryl, methyl, and ethyl esters of abietic acid, made by heating the resin acid and the alcohol under pressure until saponification takes place. The product is then distilled off under reduced pressure. These "ester gums" are being used to advantage as substitutes for copal, damar, and kauri gums in varnish making.

Uses.—Rosin is important as an ingredient of ointments and plasters, but is rarely used internally. It has been given in chronic enteritis, five grains of the powder. According to Olmstead, it has the property of preventing the oxidation of fatty substances, and thus contributes to the preservation of ointments. (A. J. P., xxii, 325.)

Off. Prep.—Ceratum Resinae, U. S. (Br.); Emplastrum Calefaciens, Br.; Emplastrum Resinae, U. S., Br.; Emplastrum Saponis, Br.; Ceratum Resinae Compositum, N. F.; Linimentum Terebinthinae (from Rosin Cerate), U. S.

The Dispensatory of the United States of America, 1918, was edited by Joseph P. Remington, Horatio C. Wood and others.