616 VANADIUM. 



semblance in properties to chromium. It combines with oxygen 

 in three proportions, forming the protoxide of vanadium, VO, 

 peroxide, VO 2 , and vanadic acid, VO 3 . 



Protoxide of vanadium, VO, 956.9 or 76.66, is produced by 

 the action of charcoal or hydrogen upon vanadic acid, It is a 

 black powder of semi-metallic lustre, and when made coherent 

 by pressure, conducts electricity like a metal. It does not com- 

 bine with acids, and exhibits none of the characters of an alka- 

 line base. It is readily oxidised when heated in the open air, 

 and passes into the following compound. 



Peroxide of vanadium, VO 2 , 1056.9 or 84.66 is produced by 

 the action of sulphuretted hydrogen and other deoxidating 

 substances upon vanadic acid. When pure, it is a black pul- 

 verulent substance, quite free from any acid or alkaline reaction. 

 It dissolves in acids, and forms salts, most of which are of a 

 blue colour. These salts give a precipitate with a slight excess 

 of carbonate of soda, of a greyish white hydrate, which becomes 

 red by oxidation. They are also precipitated black by infusion 

 of nutgalls, like the salts of iron. Peroxide of vanadium is also 

 capable of acting as an acid, and forms compounds with alkaline 

 bases, some of which are crystallizable. 



Vanadic acid, VO 3 ; 1156.9 or 92.66. It is in this state that 

 vanadium occurs in the slag of the iron of Taberg, and in the 

 vanadiate of lead. It is obtained by dissolving the latter mineral 

 in nitric acid, and precipitating the lead and arsenic, with which 

 the vanadium is accompanied, by sulphuretted hydrogen. A 

 blue solution of peroxide of vanadium remains, which becomes 

 vanadic acid when evaporated to dryness. Vanadic acid fuses 

 but retains its oxygen at a strong red heat. It is very sparingly 

 soluble, water taking up only l-100th of its weight of this com- 

 pound, acquiring a yellow colour and an acid reaction. It acts 

 the part of a base to stronger acids. An interesting double 

 phosphate of silica and vanadic acid was observed in crystalline 

 scales, of which the formula is 2SiO 3 ,PO 5 + 2VO 3 ,PO 5 -f 6HO. 

 Vanadic acid forms with bases neutral and acid salts, the first 

 of which admit of an isomeric modification, being both white 

 and yellow, while the acid salts are of a fine orange red. Va- 

 nadic and chromic acids are the only acids of which the solution 

 is red, while they are distinguished from each other by the 

 vanadic acid becoming blue, and the chromic acid green, when 

 they are deoxidised. 



