522 PRACTICAL BOTANY 



v. Some fixed oils are soluble in alcohol : e.g. oil of Ridnus 



(p. 223). 



Caoutchouc. 



i. Swollen, but not dissolved, by potash, 

 ii. Stained with tincture of alkanet. 

 iii. Soluble in chloroform or benzol. 

 Tannin. 



i. Coloured deep brown by potassium bichromate, or chromic 

 acid. 



ii. Coloured greenish-blue by solution of ferrous sulphate and 

 nitric acid. 



iii. Gives a bulky yellow precipitate with solution of ammonium 

 molybdate in strong solution of ammonium chloride. 

 Resin. 



i. Soluble more or less readily in alcohol, or ether, 

 ii. Coloured red by alkanna (p. 66). 

 iii. Coloured blue by Hanstein's aniline-violet. 



