476 BALSAMS. 



conglomerated mass, which, as long as it is warm, can 

 be moulded at desire. In this condition other sab- 

 stances, especially sulphur, can he intimately mixed 

 with it (vulcanization of caoutchouc), hy which means 

 its valuable properties are materially increased. It is 

 not fusible without decomposition. It is insoluble in 

 alcohol, soluble in ether, carbon bisulphide, and a few 

 volatile oils. Insoluble in caustic potassa. It contains 

 no oxygen, arid when subjected to dry distillation is 

 resolved almost entirely into a mixture of liquid hy 

 drocarbons. Gutta-percha is a very similar substance, 

 from various species of Isonandra in Madras. It is 

 solid at ordinary temperatures, scarcely elastic, becomes 

 soft and elastic, however, when warmed. 



3. Gum-resins. 



Important on account of their employment in medi 

 cine ; are usually mixtures of peculiar resins, fre 

 quently also caoutchouc with protein compounds, guru 

 and volatile oils. They exude from the plants as 

 milky juices or emulsions, which contain the gum or 

 protein compounds in solution, the oils and resins in 

 suspension, and besides these, frequently other sub 

 stances. ^ Of these latter may be mentioned, assafoetida, 

 euphorbium, galbanum, gamboge, myrrh, opium, etc. 

 Their consideration belongs to the field of pharma 

 cology. 



4. Balsams. 



Under this head are understood exuded or expressed 

 thick, ropy, odorous liquids from certain trees or 

 shrubs. They are either solutions of resins in ethereal 

 oils, or mixtures of substances which bear a close rela 

 tion to the latter. The following substances are bal 

 sams : 



Turpentine (p. 462). 



Canada balsam, from Abies balsamea. 



Balsam of copaiba (p. 472). 



Storax balsam (p. 372). 



Peru and Tolu balsams (p. 312). 



