326 SALTS. 



830. CHROME GREEN. On adding sul- 



Dcscribe the . . 



preparation phuric acid and a few drops of alcohol to a 



solution of bichromate of potassa, the solu- 

 tion is immediately changed from red to 

 green. The alcohol has taken oxygen from the chro- 

 mic acid, and converted it into oxide, which remains 

 in solution, as a soluble sulphate. Part of the sulphu- 

 ric acid has at the same time combined with the potassa, 

 to form sulphate of potassa. It is to the presence of 

 the sulphate of chromium in solution that the color of 

 the liquid is due. By adding an alkali to the solution, 

 a green precipitate of the hydrated oxide is produced. 

 This oxide forms a kind of " chrome green." App. 830. 



MAKGANATES. 



831. CHAMELEON MINERAL. By fusion 



What is cha- ... , 



meleon miner- with nitre, the black oxide of manganese 

 may be still further oxidized, and converted 

 into an acid. The new acid at the same time com- 

 bines with the potassa of the nitre to form manga nate 

 of potassa. This salt has been called chameleon min- 

 eral, from the spontaneous change of color which 

 takes place in its solutions. 



832. PREPARATION. The experiment 



How is chame- 



leon mineral may be made by filling a pipe stem with 

 prepare . a m j xture o f tne materials, and thrusting it 

 into burning coals. It may be made on a still smaller 

 scale before the blow-pipe, using a broken pipe-bowl to 

 support the materials. The compound dissolves in 

 water, forming a green solution, which on standing 

 is gradually changed to a beautiful red. 



