3. Resinae Terebinthinae.—Terebinthinate Resins.

1. Resina, L. E. D. [U. S.]—Rosin, or Common Resin.

(Quod restat Terebinthinae postquam oleum destillatum est, L.)

Preparation.—This is the residue of the process for obtaining oil of turpentine. It is run, while liquid, into metallic receivers coated with whiting to prevent adhesion, and from these is ladled into wooden moulds or casks. When the distillation is not carried too far, the product contains a little water, and is termed yellow rosin (resina flava). A more continued heat expels the water and produces transparent rosin; and if the process be pushed as far as it can be without producing a complete alteration of properties, the residue acquires a deep colour, and is termed brown or black rosin, or colophony (resina nigra seu colophonium). If melted rosin be run into cold water contained in shallow tanks, and a supply of cold water be kept up until the rosin has solidified, a pale yellow product is obtained, called Flockton's patent rosin.

Properties.—Rosin is compact, solid, brittle, almost odourless and tasteless, with a smooth, shining fracture, becomes electric by friction, is fusible at a moderate heat, decomposable at a higher temperature, and burning in the air with a yellow smoky flame. It is insoluble in water, but soluble in alcohol, ether, and the volatile oils. With wax and the fixed oils it unites by fusion; with the caustic alkalies it unites to form a resinous soap (the alkaline resinates, principally the pinates). Heated with concentrated sulphuric or nitric acid mutual decomposition takes place.

By distillation, rosin yields rosin oil and tar. Rosin oil is a mixture of four carburets of hydrogen: retinaphte, C14H8; retinyle, C10H12; retinale, C32H16; and metanaphthaline, C20H8. The rosin oil which distils over at from 226 ½° F. to 302° F. is a mixture of retinaphte and retinyle. It is sometimes used in the arts as a substitute for oil of turpentine. The part which boils at about 464° F. is retinole; it enters into the composition of some printing inks. Mixed with lime, it forms a sort of grease for wheels, machinery, &c. Rosin oil has been used in the preparation of rosin gas. [Pelouze and Fremy, Cours de Chimie générale, t. iii. p. 543, 1850.]

Yellow rosin is opake-and yellow, or yellowish-white. Its opacity is owing to water, with which it is incorporated. By continued fusion this is got rid of, and the rosin then becomes transparent (transparent rosin). Brown rosin, or colophony, is more or less brown and transparent.

Composition.—Rosin is a compound or mixture of pinic acid (principally), colophonic acid (variable in quantity), sylvic acid (a small quantity), and traces of an indifferent resin. [Unverdorben, in Gmelin, Hand. d. Chem. ii. 520.]

Pinic and sylvic acids are isomeric: according to Laurent, their equivalent is expressed by the formula C40H29O3, HO; and their salts by the formula MO, C40H29O3.

1. Pinic Acid.—It is soluble in cold alcohol of sp. gr. 0.883. The solution forms a precipitate (pinate of copper) on the addition of an alcoholic solution of acetate of copper. Pinate of magnesia dissolves with difficulty in water.

2. Colophonic Acid (Colopholic Acid).—Formed by the action of heat on pinic acid, and therefore the quantity of it contained in rosin varies according to the heat employed. Rosin owes its brown colour to it. It is distinguished from pinic acid by its greater affinity for salifiable bases, and its slight solubility in alcohol. [Berzelius, Traité de Chim. t. v. p. 489.]

3. Sylvic Acid.—Is distinguished from pinic acid by its insolubility in cold alcohol of sp. gr. 0.883.

4. Indifferent Resin.—Is soluble in cold alcohol, oil of petroleum, and oil of turpentine. It forms with magnesia a compound readily soluble in water.

Physiological Effects.—Not being used internally, its effects when swallowed are scarcely known. It is probable, however, that they are of the same kind as those of common turpentine, though very considerably slighter. In the horse it acts as a useful diuretic, in doses of five or six drachms. [Vouatt, The Horse, In the Library of Useful Knowledge.] Its local influence is mild. "It may be considered," says Dr. Maton, [Lambert's Pinus.] "as possessing astringency without pungency."

Use.—Powdered rosin has been applied to wounds to check hemorrhage, and is occasionally used for this purpose in veterinary practice. But the principal value of rosin is in the formation of plasters and ointments, to which it communicates great adhesiveness and some slightly stimulant properties.

1. CERATUM RESINAE, L. [U. S.]; Unguentum Resinosum, E.; Unguentum Resinae, D.; Yellow Basilicon or Basilicon Ointment, offic.—(Resin, Wax, of each, ℥xv; Olive Oil Oj. Melt the resin and the wax together with a slow fire; then add the oil, and press the cerate, while hot, through a linen cloth, L.—The Edinburgh College orders of Resin ℥v; Axunge ℥viij; Bees' Wax ℥ij. Melt them together with a gentle heat, and then stir the mixture briskly while it cools and concretes. [The U. S. Pharm. directs the same.]—The Dublin College orders of Resin, in coarse powder, lb ss; Yellow Wax ℥iv; Prepared Lime lb j.)—A mildly stimulant, digestive, and detergent application to ulcers which follow burns, or which are of a foul and indolent character, and to blistered surfaces to promote a discharge.

2. EMPLASTRUM RESINAE, L. D. [U. S.]; Emplastrum Resinosum, E.—Has been already described at vol. i. p. 715.

2. Pix Burgundica, L. E. D.—Burgundy Pitch.

(Resina impura e terebinthina praeparata, L.)

Preparation.—True Burgundy pitch is prepared by melting common frankincense (Abietis resina; Thus) in hot water, and straining through a coarse cloth. By this process part of the volatile oil and the impurities are got rid of. The substance sold as Burgundy pitch in the shops is rarely prepared in this way, but is fictitious. Its priucipal constituent is rosin, rendered opake by the incorporation of water, and coloured by palm oil. One maker of it informed me that he prepared it from old and concrete American turpentine.

I have a sample of genuine Burgundy pitch prepared by Mr. D. Hanbury from Thus collected by himself in Switzerland (see ante, p. 290). In colour it somewhat resembles emplastrum plumbi. Its odour resembles the Burgundy pitch imported from Hamburgh, and which, when strained, constitutes the best commercial Burgundy pitch.

Hamburgh Burgundy pitch is of a dark colour, and contains many impurities. It would appear to be melted but unstrained Thus. It yields, when re-melted and strained, a Burgundy pitch which is darker coloured, but which otherwise agrees with the genuine sample prepared by Mr. Hunbury.

Properties.—Genuine Burgundy pitch is hard, brittle when cold, but readily taking the form of the vessel in which it is kept. It softens by the heat of the hand, and strongly adheres to the skin. Its colour is yellowish-white; its odour is not disagreeable; its taste slightly bitter. Fictitious Burgundy pitch is usually of a fuller yellow colour than the genuine, and has a somewhat less agreeable odour.

Composition.—Consists of resin principally and a small quantity of volatile oil.

Physiological Effects.—Its effects are similar to those of the other terebinthinate resins. In activity it holds an intermediate station between common turpentine and rosin; being considerably less active than the first, and somewhat more so than the last of these substances. Its local action is that of a mild irritant. In some persons it excites a troublesome vesiculo-pustular inflammation. [Rayer, Treatise on Diseases of the Skin, by Dr. Willis, p. 366.]

Uses.—It is employed as an external agent only, spread on leather, forming the well-known Burgundy pitch plaster (emplastrum picis burgundicae), which is applied to the chest in chronic pulmonary complaints, to the loins in lumbago, to the joints in chronic articular affections, and to other parts to relieve local pains of a rheumatic character. It acts as a counter-irritant or revulsive.

EMPLASTRUM PICIS, L. E.; Plaster of Pitch.—(Burgundy Pitch lb ij; Frankincense [Thus] lb j; Resin, Wax, of each ℥iv; Expressed Oil of Nutmeg ℥j; Olive Oil, Water, of each f℥ij. Add the oils and water to the pitch, resin, and wax, melted together. Lastly, mix them all, and boil down to a proper consistence, L.—The formula of the Edinburgh College is as follows: Burgundy Pitch lb jss, Resin and Bees' Wax, of each ℥ij; Oil of Mace ℥ss; Olive Oil f℥j; Water f℥j. Liquefy the pitch, resin, and wax, with a gentle heat; add to the other articles; mix them well together, and boil till the mixture acquires a proper consistence.)—Stimulant and rubefacient; used in the same cases as the simple Burgundy pitch.

The Elements of Materia Medica and Therapeutics, Vol. II, 3th American ed., was written by Jonathan Pereira in 1854.