M. Berzelius on Vanadium. 333 



Sulphate of Vanadium. — This salt is obtained by dissolving 

 vanadic acid or oxide (as obtained by the calcination of vana- 

 date of ammonia) in sulphuric acid, mixed with an equal 

 quantity of water, and by passing sulphuretted hydrogen into 

 the solution diluted with water, in order to reduce the last 

 traces of the vanadic acid dissolved. Oxalic acid may be used 

 for the same purpose ; the liquid is to be evaporated until the 

 excess of sulphuric acid begins to concentrate; the salt is then 

 deposited in the form of a transparent crystalline crust of a 

 dirty blue colour. The excess of acid is to be drained from 

 the salt, and then it is to be washed with absolute alcohol. 

 The salt gradually swells, and is reduced to a light crystalline 

 powder of an ultramarine blue colour; it is then washed with 

 alcohol, which it always renders of a blue colour, although 

 but a very small quantity is dissolved. It is afterwards dried 

 by being placed under a receiver, with a vessel containing 

 sulphuric acid or chloride of calcium. An essential difference 

 appears to exist between the salt which crystallizes in the 

 coicentrated acid and the blue pulverulent salt; but I do not 

 know in what it consists. It is probable that the former is a 

 supersalt ; for the blue powder which I analysed is neutral 

 sulphate. In this state sulphate of vanadium appears but 

 slightly soluble in cold water; it first diffuses itself through 

 it, and dissolves with extreme slowness, but in hot water it 

 tlissolvcs readily : the supersulphate is deliquescent in warm 

 moist air, and becomes of a syrupy consistence; while the same 

 quantity of sulphate, kept under water, remains almost en- 

 tirely insoluble. It is rather difficult to obtain this salt in 

 regular crystals. 



The best method of crystallizing it is to let the dry sulphate 

 deli(juesce, and to suffer it to remain for some weeks. A very 

 slight excess of acid often favours the experiment, which 

 never succeeds in moist weather. The crystals consist prin- 

 cipally of an aggregation of prisms; but I obtained some 

 which were very short simple right prisms with rhombic bases, 

 having small triangular oblique facets at the summit of each 

 acute angle. Their colour resembles the fine bkie of sulphate 

 of copper, but is perhaps rather deeper. This salt contains 

 17"9 per cent, of water, the oxygen of which is to that of 

 the base as 2 to I. This also is the composition of the pow- 

 der precipitated by alcohol. Sulphate of vanadium is decom- 

 posed by lieat; the oxide is converted into vanadic acid at 

 the expense of the sulphuric acid ; sulphurous and anhydrous 

 sul|)huric acid are disengaged, and fused vanadic acid re- 

 mains. If hydrate of vanadium be digested in a slightly con- 

 centrated solution of the sulphate, the l)ydrute is dissolved, 



and 



