438 ON GRASS-TREE GUM, 



alcohol has a brownish-yellow colour ; the addition of water 

 precipitates it as a dark yellow mass, but it does not crystallize 

 out of its alcoholic solution when left to spontaneous evaporation, 

 but remains as a varnish. When digested with strong alkaline 

 lyes, it readily dissolves and forms a brownish-red solution ; and 

 when the alkali is neutralized with muriatic acid, the resin is 

 precipitated considerably altered as a dark brownish brittle mass, 



" Oa concentrating the solution out of which the resin has 

 been precipitated, and allowing it to cool, a quantity of impure 

 reddish crystals resembling benzoic acid are gradually deposited. 

 It requires repeated and long-continued digestions with the 

 strongest alkaline lyes to remove the whole of this crystalline 

 acid from the resin, which retains it with very great tenacity. 

 The quantity of the acid is by no means great. It is not easily 

 purified, as its crystals are apt to retain a trace of a reddish 

 colouring matter, from which it is very difficult to free them. 

 The easiest way of getting rid of it is by dissolving the impure 

 crystals in a small quantity of alcohol and then adding water ; 

 the greater poi-tion of the colouring matter is retained in solution, 

 while the crystals are precipitated tolerably white. When purified 

 by repeated crystallizations, they become quite colourless. In 

 appearance, taste, and smell, they closely resemble benzoic acid. 



" The quantity of carbazotic (picric) acid which Botany Bay 

 resin yields when treated with nitric acid is so great, and it is so 

 easily purified, that this resin seems likely to prove the best 

 source* of that substance. When the resin is subjected to des- 

 tructive distillation in an iron or copper retort, it yields a very 

 large quantity of a heavy acid oil mixed with a very small quantity 

 of a neutral oil, which is lighter than water. If, however, the 

 resin has been previously digested with alkaline lyes, so as to 

 remove all the cinnamic and benzoic acids it contains, the heavy 

 oil is obtained as before, but none of the light essential oil. The 

 acid oil is readily soluble in soda and potash lyes; in its smell and 

 properties it resembles creosote ; when it is digested with nitric 



* Superseded by coal-tar now, of course. 



