RESINS PROPER. 471 



most various portions of plants, mostly in company 

 with volatile oils, dissolved in which they frequently 

 flow from trees from accidental or intentional cuts. 

 The crude resins are never crystallized ; they have the 

 form of drops, like gum ; are colored mostly yellow or 

 brown; translucent, brittle, with a shiny, conchoidal 

 fracture ; often possessing a weak smell and taste. In 

 a pure state they are colorless, inodorous, and tasteless; 

 several are then crystallizable. They are fusible, in- 

 flammable, not volatile, non-conductors of electricity; 

 insoluble in water, soluble in alcohol, in ether and 

 volatile oils. 



Most resins, occurring in nature, consist of several 

 simple compounds, which, however, as a rule, are 

 exceedingly difficult to separate and prepare in a pure 

 condition. 



Most resins are weak acids or anhydrides of acids. 



The number of resins is very large. Only a few of 

 them, which are of importance on account of technical 

 or pharmaceutical employment, are investigated. 



The conduct of a great many resins, when heated 

 with fusing potassa (to 1 part of resin 3 parts potassa), 

 is of interest. They then yield, as a rule, together 

 with fatty acids: protocatechuic acid (p. 356), paraoxy- 

 benzoic acid (p. 347), phloroglucin (p. 311), and resorcin 

 (p. 306.) 



1. Resins Proper. 



I. Colophony (Pine-resin). The turpentine, which 

 flows from the pines, firs, larches, and other species of 

 Pinus, solidifies gradually on the trees, forming a resin, 

 partially by evaporation, partially by oxidation of the 

 oil. Distilled with water, oil of turpentine passes 

 over, the resin remains behind ; it is known under the 

 name of colophony. 



Colophony is brownish-yellow, translucent, brittle, 

 fusible ; easily soluble in alcohol, ether, fatty and vola- 

 tile oils. When it is digested for several days with 

 ordinary alcohol (at the strongest 70 per cent.), filtered 

 hot, and water added to the filtrate until a slight 



