40 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



oleo-resin of trees tapped for the first time; and (2) a yellowish-red 

 or reddish-brown variety derived from the oleo-resin of trees that 

 have been tapped for a number of years. The former article is pre- 

 ferred. 



Description. Usually in sharp, angular fragments; translucent, 

 amber-colored, usually covered with a yellowish dust, hard, brittle 

 pulverizable, fracture shiny and shallow-conchoidal; odor and 

 taste faintly terebinthinate. 



Rosin has a specific gravity of 1.070 to 1.080, and it is soluble in 

 alcohol, ether, benzol, carbon disulphide, acetic acid, fixed and 

 volatile oils and in solutions of potassium or sodium hydrate. 



On heating a small quantity of colophony and neutral methyl 

 sulphate or neutral ethyl sulphate in a test-tube the mixture assumes 

 a rose, then violet and finally a deep violet color. 



Powder. Pale to dark yellow; irregular fragments, soluble in 

 alcohol, forming a straw-colored liquid, which becomes milky-white 

 on addition of water; on heating fragments of rosin in water they melt, 

 flow together and form a sticky mass. 



Constituents. From 80 to 90 per cent of an anhydride of abietic 

 acid, which, on treatment with alcohol, is changed into abietic acid, 

 which latter is crystalline; sylvic acid, which is probably a decom- 

 position product of abietic acid; ash, about 1 per cent. 



White rosin, prepared by agitating melted rosin in water, occurs 

 in whitish, opaque masses, due to inclusion of air. 



Rosin is not infrequently used as an adulterant of other resinous 

 products, as of Burgundy pitch and Venice turpentine. A mixture 

 of rosin and oil of turpentine is sometimes substituted for the latter. 



Resins are a class of substances which may be looked upon as 

 final products in destructive metabolism. They result from the 

 oxidation of oils and allied products and usually accompany them, 

 as oleo-resins, gum-resins, etc. They are insoluble in water, solu- 

 ble in alcohol, acetone, ether and similar solvents, and burn with a 

 yellow flame, forming considerable soot. Several kinds of resins 

 are recognized, depending upon the nature and constitution of their 

 important constituents : 



(1) Resinolic Acid Resins include those that contain a large 

 proportion of oxy-acids, and have been obtained in a crystalline 

 condition, as abietic acid in colophony; copaivic and oxy-copaivic 

 acids, in copaiba; guaiaconic acid, in guaiac; pimaric acid in Bur- 

 gundy pitch and frankincense; and sandaracolic acid, in Sandarac. 



(2) Resinol Resins are alcoholic or phenolic resins, a number of 

 which have been crystallized, as benzoresinol, from benzoin; stores- 



