454 RESINS 



large quantities of oleo-resin which, discharged over the wound, forms 

 a temporary protection for it. This flow of oleo-resin, which is 

 termed ' secondary flow ' to distinguish from the * primary flow ' from 

 ducts normally present, is the source of most of the oleo-resins of 

 tschnical importance. 



None of the resins are simple bodies ; all are mixtures, and most 

 of them are mixtures of complex nature. 



The following are the chief classes of substances that have been 

 isolated from the resins : 



1. Resinotannols : aromatic, amorphous, brownish resin-alcohols 

 allied to the tannins ; they occur partly free, but more generally 

 combined with aromatic acids or with umbelliferone in the form of 

 esters (tannol-resins) . 



2. Resinols : crystalline, colourless resin-alcohols, also occurring 

 partly free, partly in the form of esters (resinol-resins) . 



3. Resin-acids : these are partly crystalline, and mostly occur free ; 

 they combine with alkalies to form soaps, and with metals to form 

 esters that often crystallise readily. 



4. Resenes : these are indifferent bodies, and neither esters nor acids. 



5. Glucoresins : these yield sugar by hydrolysis. 



6. Various acids, more particularly belonging to the aromatic 

 series, such as benzoic, cinnamic, paracumaric, salicylic, &c., which 

 occur partly free and partly combined with the resin-alcohols. 



The resins dealt with in this volume may be conveniently grouped 

 according to their constituents, thus colophony, Burgundy pitch, 

 sandarac, and amber are all of Coniferous origin, and present many 

 points of analogy. Guaiacum contains chiefly resin-acids, and in 

 mastich the principal constituent is a resene. Benzoin and dragon's 

 blood contain resin-alcohols (resinols) together with aromatic acids. 

 In shellac fatty resins are present while araroba, consisting almost 

 entirely of crystalline substances, is not, strictly speaking, a resin, 

 although it may conveniently be appended. 



COLOPHONY 



(Amber Resin, Resm> Resina) 



Source, &c. Colophony is the residue left after the distillation of 

 the oil of turpentine from the crude oleo-resin of various species of 

 Pinus (N.O. Coniferce). 



Most Coniferous trees contain in the wood a branching system of 

 schizogenous secretion ducts filled with a viscid oleo-resin, which is 

 exuded when the ducts are punctured. The amount thus yielded is, 

 however, small. Very much larger quantities, practically the entire 

 yield, are obtained by hacking the bark of the tree. In the new wood 

 produced by the cambium immediately after such injury large numbers 



