M. Berzelius on Vanadium. 335 



acid be Baturated widi hydrate of vanadium, a very concen- 

 trated solution is obtained, which furnishes by evaporation a 

 crystallized neutral salt, and also a gummy mass which appears 

 to be a subsalt. Alcohol acts upon the arseniate in the same 

 manner as upon the phosphate. 



Borate of Vanadium.— K solution of borax precipitates the 

 salts of vanadium of a brownish gray colour. This precipi- 

 tate is dissolved by an excess of boracic acid. The solution 

 is blue, but it soon becomes green in the air. If an attempt 

 is made to restore the blue colour by passing a current of sul- 

 phuretted hydrogen into it, oxide of vanadium and subsul- 

 phuret are formed, which remain dissolved in the boracic 

 acid, and colour the solution of an intense brown. Sulphuric 

 acid quickly precijntates this solution, and the precipitate 

 consists of subsulphuret of vanadium. Subjected to spon- 

 taneous evaporation in the air, the solution soon becomes 

 green, and leaves at last a solid mixture, of a greenish brown 

 colour, of sulphate and vanadate of vanadium, sulphur, and 

 boracic acid in crystalline scales. 



Carbonate of Vanadium. — It appears that this salt cannot be 

 obtained in the moist way. I have stated above that the pre- 

 cipitate formed by the alkaline carbonates in the salts of vana- 

 dium consists of hydrate free from carbonic acid, or contains 

 only traces of it ; the presence of carbonic acid depends upon 

 accidental circumstances, as happens with the oxides of cobalt 

 and nickel. 



Silicated Vanadium. — Ttepared by double decomposition; 

 this salt forms a greyish precipitate, which becomes green by 

 drying. Water does not separate anything from the green 

 jiowder. 



Molybdate of Vanadium.— VJhen sulphate of vanadium is 

 mixed with molybdate of ammonia, both in solution, a liquid 

 of a fine purple colour is obtained similar to that of tungstate 

 of molybdenum. On this account I imagined that there was 

 an exchange of oxygen, and that vanadate of molybdenum was 

 formed. But when a molybdate is mixed with vanadate of 

 ammonia, it becomes yellow and not purple. The purple 

 colour disappears gradually in the air; it is at first replaced by 

 blue, then by green, and la'sdy by yellow, without the solution 

 becoming turbid. 



Tungstate of Vanadium.— Uns salt is precipitated in the 

 form of a brownish yellow powder. It dissolves in a suflicient 

 quantity of water, and when it is left in die liquid it dissolves 

 widiout the addition of water, in jiroportion as the oxide of 

 vanadium acidifies. The solution eventually contains a yellow 

 combination of the two acids. 



Chromate 



