50 
“Note on Meta-Vanadic Acid,” by Dr. B. W. Gerland. 
Communicated by Professor Boscoe, F.B.S. 
A solution of copper vanadiate in aqueous sulphurous acid, 
after part of the latter is removed by boiling, deposits bril- 
liant yellow crystals, 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 
change 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 water 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 VH0 3 , which requires— 
Water 8.97 
Vanadic pentoxide 91.03 
100.00 
