M. Berzelius on Vanadium. 9 



water and evaporated with heat, when they have suffered a 

 certain degree of concentration, deposit an iincrystallized 

 I'eddish-brown mass, which is a kind of subsalt : many of 

 the persaks of vanadium become colourless when heated ; a 

 change which ajipears to be of the same nature as that which 

 occurs with many vanadates hereafter to be mentioned. The 

 persaks in solution, when exposed for some time to the air, 

 become gradually green, probably by the partial reduction 

 which vanadic acid sufiers by the dust of the air. The per- 

 salts of vanadium are rendered blue by a great many deoxi- 

 dizing bodies ; such as sulphuretted hydrogen, alcohol, sugar, 

 many vegetable acids, tannin, &c. ; the last mentioned gives 

 them so deep a blue colour that it appears black; but after 

 dilution with water, the solution is of a very pure blue colour, 

 although extremely deep. Ferrocyanate of potash gives a 

 green precipitate. 



Persulphate of Vanadium. — To prepare it in a neutral state, 

 vanadic acid is to be dissolved in sulphuric acid diluted with its 

 weight of water, heating the mixture slightly with a spirit-lamp, 

 and finishing by evaporating the excess of acid at the lowest 

 temperature possible. When the mass ceases to fume, it is to 

 be suffered to cool; the sulphate remains in the form of cry- 

 stalline scales of a reddish-brown colour ; it is extremely de- 

 liquescent, and in a few hours attracts sufficient moisture to 

 have the consistence of a syrup, which is transparent and red, 

 and which may be diluted with water or alcohol, and I'emains 

 clear. The solution in water is of a pale yellow colour ; heated 

 to ebullition, it deposits a red mass which is a subsalt; the 

 liquid portion when evaporated gives a syrupy red mass, con- 

 taining excess of acid. A soluble subsalt is obtained when 

 the neutral sulphate of vanatlium is dissolved in nitric acid, 

 and evaporated to dryness. The subsalt is deliquescent, and 

 its solution in water is nearly colourless. 



Persulphate of Vanadium and Potash. — This salt is obtained 

 by adding to a solution of vanadate of potash, the requisite 

 quantity of sulphuric acid. The double salt is deposited by 

 slow evaporation in small mammellated yellow grains, which 

 are soluble in water and insoluble in alcohol. 



Peniitrate of Vanadium. — Nitric acid dissolves but very 

 little vanadic acid ; it has a pale yellow colour. By sponta- 

 neous evaporation, the nitric acid separates almost entirel}^ 

 Nevertheless the dried mass yields a little pernitrate of vana- 

 dium to water. 



Perphosphate of Vanadium. — In order to obtain this salt, 

 phosphate of vanadium is to be dissolved in nitric acid ; the 

 solution is to be evaporated until it becomes of a deep red 



N.S. Vol. 11. No. 61. Jan. 1832. C colour, 



