328 M. Berzelius on Vanadium. 



quantity of water, it becomes of a green colour, which is beau- 

 tiful, but so deep that the solution appeares opake. The solu- 

 tion, when filtered and evaporated in vacuo, leaves a blackish 

 cracked residue, without any trace of crystallization, and which 

 is completely resoluble in water. This same combination is ob- 

 tained, when a solution of a neutral salt with abase of oxide of 

 vanadium is mixed with neutral vanadate of potash. If the 

 solutions are moderately concentrated, a great part of the new 

 green compound formed is deposited in the state of deep co- 

 loured powder; and if the solution is too dilute to give a 

 precipitate, one is obtained by dissolving sal ammoniac in it. 

 The precipitate is insoluble in absolute alcohol, but it dissolves 

 in alcohol of 0"86. The solutions of this substance diluted so 

 as to become perfectly transparent, have a very fine green 

 colour. A small quantity of alkali deepens the colour, but 

 does not destroy the green compound. The addition of a 

 caustic alkali in excess occasions in a short time a brown pre- 

 cipitate, which is a vanadate of the alkali added. The carbo- 

 nates of soda and potash change the green colour to brown, 

 without precipitating anything; an excess of carbonate of 

 ammonia does not destroy the colour. Vanadic oxide, mixed 

 and digested with vanadic acid, forms the same compound, 

 which may also be produced in the dry way by heating an 

 intimate mixture of lOy parts of oxide, and 23^^^ parts of va- 

 nadic acid. The mixture fuses, and gives a glass of a deep green 

 colour, the powder of which dissolves gradually in water. 



c. Bivanadate of Vanadium. — This compound is obtained 

 by mixing a neutral salt of vanadium with one of bivanadate 

 of potash ; this salt is solid and green like the preceding, the 

 tint of which is deeper ; its solution in water is of yellowish 

 green. It is less soluble than the preceding, and is more com- 

 pletely precipitated by sal ammoniac. 



d. Supervanadate of Vanadium. — All the purple and green 

 compounds oxidize in the air, especially when they are very 

 dilute. Their colour becomes first greenish yellow, and after- 

 wards orange yellow. By spontaneous evaporation, they yield 

 crystals of a pale orange yellow coloiu", which lose their water 

 and become green when heated in the fire; 22*5 parts of water 

 dissolve one part of this orange compound, consequently it is 

 much more soluble than vanadic acid alone. 



Sulphurets of Vanaditim. — The affinity of vanadium for sul- 

 phur is but weak at moderately high temperatures ; it may be 

 mixed with sulphur, and the mixture may be distilled without 

 undergoing combination ; and even when it is heated to red- 

 ness in an atmosphere of sulphur, vanadium is not sulphu- 

 retted. 



