18 
PROFESSOR ROSCOE’S RESEARCHES OH VANADIUM. 
of vanadic acid have been fully described by Berzelius ; the only important addition to 
our knowledge of this oxide made since his time is the determination of the crystalline 
.form (rhombic prisms) made by Nordenskjold*. In the present communication I 
propose to discuss the properties and composition of vanadic acid and the vanadates only 
so far as is necessary for the purpose of elucidating the true atomic weight of the metal. 
Constitution of the so-called Monovanadates. — The analyses made by Berzelius of the 
ammonium and barium vanadatesf suffice to point out the true character of these salts. 
The formulse which he there gives, assuming the atomic weight of the metal to be 68-5, 
show that these compounds must be considered as metavanadates when the atomic 
weight of the metal is taken to be 5T3. 
Berzelius’s formulae. V= 68-5, 0=8. 
Vanadiate of ammonia, NH 3 V 0 3 +H O. 
Vanadiate of baryta, Ba O V 0 3 . 
New formulae. V=51-3, 0 = 16. 
NH.V Oo, ammonium metavanadate, or ^ ^ 4 1 0 9 . 
4 3 VO ) 2 
Ba V 2 0 6 , barium metavanadate, or 
Ba) 
2V0J 
In order to confirm Berzelius’s analysis of the ammonium salts, the following analyses 
were made of the white anhydrous salt obtained by blowing ammonia gas into water 
containing suspended vanadic acid, and repeatedly crystallizing. The ammonium salt, 
on careful roasting in a platinum boat in a current of oxygen gas, yielded vanadium 
pentoxide, which was fused and 
weighed. 
Weight of ammonium 
Weight of pentoxide 
Percentage of 
Calculated 
Nos. 
salt taken. 
obtained. 
pentoxide found. 
percentage. 
1 . 
6-8531 
5-3263 
77-72 
77-82 
2. 
2-0445 
1-5902 
77-78 
3. 
2-6129 . 
2-0314 
77-75 
Berzelius found 77*59 per cent, of vanadic acid. The analysis of the ammonium 
metavanadate, if accurately made, serves likewise as a check on the atomic weight deter- 
minations. If a represent the weight of the salt taken, and b that of the vanadium 
pentoxide obtained, the atomic weight of vanadium is found from the equation 
_ r 666— 40fit 
V= T 
a—b 
From No. 1. V= 50-65. 
From No. 2. V=5T06. 
From No. 3. V=50 - 82. Mean result 50-84. 
Constitution of the so-called Bivanadates. — The bivanadates obtained by the cautious 
addition of acetic acid to the monovanadates, according to Berzelius’s directions, have 
* Pogg. Ann. Bd. cxii. p. 160. + Ibid. Bd. xxii. p. 49. 
