“ The resins which are obtained as natural exudation’s are in general mixtures of different, peculiar acids, named the resin acids, which dissolve in alkalis to form resin soaps, from which the resin acids are regenerated by treatment with acids. They are closely related to the terpenes, with which they occur in plants and of which they are oxidation products. Examples of resin acids, are abietic (sylvic) acid, C19H28O2, occurring in colophon, and pimaric acid, C20H30O2, a constituent of gallipot resin. ”

“ The general conception of a resin is a noncrystalline body, insoluble in Water, mostly soluble in alcohol, essential oils, ether and hot fatty oils, softening and melting under the influence of heat, not capable of sublimation, and burning with a bright, but smoky flame. A typical resin is a transparent or translucent mass, with a vitreous fracture and a faintly yellow or brown colour, in odorous or having only a slight turpentine odour and taste. ”