50 



"Note on Meta-Vanadic Acid," hy Dr. B. W. Gerland. 

 Communicated by Professor RoscoE, F.KS. 



A solution of copper vanadiate in aqueous sulphurous acid, 

 after part of the latter is removed by boiling, deposits bril- 

 liant yellow cr^^stals, the description and analysis of which I 

 gave in the Journ. of Pract Chem., 1871, page 97. These 

 crystals are quite uniform in appearance and contain cupric 

 oxide, vanadic acid, and sulphurous acid. They rapidly 

 ciiano-e under the influence of air, their beautiful metallic 

 lustre soon disappears, and the colour becomes a dark green. 

 Although formed in a solution of sulphurous acid, they 

 nevertheless decompose when treated, after separation from 

 their mother liquor, with fresh sulphurous acid, so that two 

 kinds of crystals, brown and orange yellow, now appear 

 mixed together. An excess of sulphurous acid dissolves the 

 the former and leaves the latter intact. After filtration, 

 washing, and drying, they form microscopic scales of beauti- 

 ful lustre and a deep yellow orange colour ; they are free from 

 copper and sulphur, and perfectly unalterable in the air. 

 Heated to 100° C. and even to 130", they lose no weight, 

 but at a low red heat Avater is given off, and the residuum 

 consists of vanadium pentoxide, which fuses and crystallizes 

 after cooling. 



The composition of the substance, previously dried over 

 vitriol, is according to analysis the following : 



Water (loss by heating) 8.73 



Vanadium pentoxide 91.06 



Impurities 0. 2 1 



100.00 



These numbers correspond to the formula of the meta- 

 vanadic acid VHO3, which requires — 



Water 8.97 



Vanadic pentoxide 91.03 



100.00 



