180 On pure Caoutchouc. [1826. 



The solution (b) was almost tasteless, and when dried left a 

 green, shining, brittle substance, resoluble in water, and of 

 course precipitable by alcohol. It colours solution of persul- 

 phate of iron green ; but if its strong aqueous solution be treated 

 with muriatic acid, a reddish-brown precipitate is formed, 

 which, when separated, dissolves in water, does not colour per- 

 salts of iron, and when evaporated yields a pulverulent sub- 

 stance, burning, but not with facility, and producing a little 

 ammonia when heated in a tube. 



The alcoholic solution from which these matters had been 

 separated contained the particular principle which colours per- 

 salts of iron green. When evaporated it left a brown, brittle, 

 transparent substance, becoming soft by exposure to moist air. 

 It is very bitter, soluble in water, &c., slightly acid. When 

 heated on platina-foil, it does not burn easily, but runs out into 

 a bulky charcoal, much like animal matter ; at the same time it 

 does not yield ammonia when heated in a tube per se, though 

 the smell is very like that of animal substance. 



Ether warmed with it dissolved a small portion of matter, and 

 the solution, upon evaporation, left globules, which, in all their 

 characters, corresponded with wax ; its quantity was but small. 



Nine hundred and eighty-one grains of the original sap were 

 washed in water several times. The washed caoutchouc, being 

 coagulated by heat and perfectly dried, weighed 311 grains. 

 The aqueous solutions, upon being boiled, yielded sufficient of 

 the heavy precipitate to equal, when dried, 18*6 grains. The 

 clear solution was now evaporated to dryness and digested in 

 alcohol, 28'5 grains of insoluble matter were left, and the solu- 

 tion, upon evaporation, afforded 70 grains of dry matter. Hence 

 the following are the contents nearly of 1000 parts of the ori- 

 ginal sap : 



Caoutchouc 317'0 



Albuminous precipitate 19*0 



Peculiar bitter colouring matter, al 



highly azotated substance . . >* 71*3 



Wax J 



Substance soluble in water, not in alcohol 29*0 



Water, acid, &c 563-7 



1000-0 



