12 M. Berzelius on Vanadium. 



in my laboraton*, without its becoming vanadate. The dried 

 mass, although ot" a deep colour, shines almost like the marga- 

 rine of soaps. It dissolves easily in water, and the solution is 

 of so deep a colour that it is scarcely translucid. Potash 

 precipitates vanadite of potash from water, in the state of a 

 brown powder. With the assistance of heat, the salt dis- 

 solves in the liquor, and afterwards crystallizes again. The 

 alkaline liquor retains a yellowish colour; in a few days it is 

 converted by exposure to the air into a colourless vanadate. 



Vanadite of Ammonia. — This salt is prepared like the last; 

 but it is so insoluble in a liquid which contains excess of am- 

 monia, that it precipitates perfectly, and leaves the liquor co- 

 lourless ; when separated from the mother-watei', it dissolves 

 readily in pure water and forms a brown solution. In vacuo it 

 appears to lose its ammonia ; for after drying in it, water does 

 not dissolve it. 



The vanadites of the earths and metallic oxides are inso- 

 luble, and precipitate in the state of a brown powder, when a 

 neutral solution of them is mixed with a neutral solution of 

 crystallized vanadite of potash. They soon become green 

 when washed upon a filter. As it is extremely difficult to 

 precipitate vanadium from solutions containing it, so as to de- 

 termine its weight, advantage is taken of the insolubility of the 

 vanadites to effect this purpose, by precipitating oxitle of 

 vanadium in combination vidth other oxides, particularly with 

 peroxide of mercury. With this intention a solution of a 

 vanadite is mixed with one of perchloride of mercury, and 

 precipitated by ammonia. The precipitate consists of a mix- 

 ture of pervanadite of mfercury and muriate of ammonia and 

 mercury ; when this is heated in a platina crucible, vanadic 

 acid remains, containing a little peroxide of mercury. They 

 are separated by dissolving the acid in ammonia. 



Vanadates. — These salts may exist of various degrees of 

 saturation. In the neutral vanadates, the oxygen of the base 

 is to that of the acid as 1 to 3 ; in bivanadates as I to 6 ; but 

 there are supervanadates in which the proportion of the acid 

 to the base is still greater. The neutral vanadates with stronger 

 bases, such as the alkalies, alkaline earths, the oxides of lead, 

 cadmium and zinc, are colourless. The bivanadates are orange- 

 coloured, and the supervanadates are brownish red. 



With respect to colour, the vanadates have this peculiarity, 

 — they are originally yellow, but they lose this colour sponta- 

 neously. The vanadates of the fixed alkalies lose it in some 

 hours, and those of the other bases in twenty-four hours ; this 

 change occurs in some cases in a few seconds, when heated 

 to 212° Fahrenheit. This loss of colour appears to be an 



isomeric 



