474 GUAIACUM. 



9. Olibanum (Incense), from a species of Boswellia, 

 a tree in Abyssinia. Subglobular, pale-yellow, trans- 

 lucent grains ; for the greater part soluble in alcohol ; 

 fusible with decomposition, and emitting a balsamic 

 odor. 



10. Sandarac, from Thuja articulata, in Barbary. 

 Small, pale-yellow, translucent, brittle grains ; easily 

 fusible ; soluble in alcohol. 



11. Gum-lac is produced in consequence of the 

 sting of an insect (Coccus laced) in the branches of 

 certain trees in the East Indies. When still on the 

 branches it is called in commerce stick-lac, separated 

 from them seed-lac, and in a purified, melted condition 

 shell-lac, in which state it forms thin, brittle, brown, 

 translucent pieces. Gum-lac contains several other 

 products, originated by the insects, especially a color- 

 ing principle and fats. 



12. Benzoin-gum, from Styrax benzoin, a tree 

 growing in Sumatra. Large, brittle lumps, which, on 

 the fractured surface, appear to be conglomerated of 

 smaller white and brownish pieces. It has a pleasant 

 vanilla-like odor, evolves vapors of benzoic acid when 

 heated, which forms about 18 per cent, of the gum. 

 Some varieties contain cinnamic acid in addition to 

 benzoic. 



13. Guaiacum, from Guajacum officinale, a tree 

 growing in the West Indies. Large, translucent, 

 brittle lumps, externally bluish-green, on the fractured 

 surface brown. Its powder becomes green in contact 

 with the air, or under the influence of chlorine-water. 

 Its solution in alcohol becomes deep blue when acted 

 upon by ozone, nitrous acid, chromic acid, iron sesqui- 

 chloride, etc. 



The principal ingredient of guaiacum is a weak 

 bibasic acid, crystallizing from acetic acid in concen- 

 trically arranged needles, guaiaretic acid, C 20 H 26 O, 

 which fuses at 75-80, and by slow distillation is re- 

 solved into pyroguaiacin, C 19 II 22 3 , a crystalline sub- 



