PROFESSOR ROSCOE’S RESEARCHES 02s T VANADIUM. 
17 
0-8112; on March 25th the colour had become blue and the weight of the oxide was 
0-8267, showing a percentage increase of 10-13, or an absorption of nearly one atom of 
oxygen, as 100 of trioxide require 11-87 of oxygen for conversion into the pentoxide. 
On further exposure the blue oxide increases in weight, again changes colour to a dark 
olive-green, and a hydrated oxide is formed. 
Vanadium Tetroxide in solution . — Solutions of the salts of vanadium tetroxide are 
bright blue as described by Berzelius. They may be obtained (1) by the action of 
moderate reducing agents, such as sulphur dioxide and sulphuretted hydrogen (probably 
also oxalic acid, sugar, alcohol, &c.) upon solutions of vanadium pentoxide in sulphuric 
acid, (2) by the action of a current of air upon the acid solution of vanadium sulphate. 
(1) If sulphur dioxide or sulphuretted hydrogen be passed into the yellow solution of 
vanadium pentoxide in dilute sulphuric acid, the liquid becomes permanently blue, no 
green or violet colour being obtained by the continued action of these reducing agents. 
In order to determine the state of oxidation of the metal, these blue solutions were boiled 
in an atmosphere of carbonic acid until every trace of the reducing agent was expelled, 
and on cooling standard permanganate was added until the pink tint was noticed. 
Reduced by S 0 2 . 
Reduced by SH 2 . 
a 
r ~Q) (2~P 
(3) 
(4) (5) 
(6) 
Weight of V 2 0 5 taken . . 
Cub. centim. permanganate) 
0-1062 
| 
0T106 
0-1060 
0-1248 
0-1489 
0T239 
required (1 cub. centim. 
=0-0014130) . . . J 
6-7 
7-0 
6-8 
8-3 
9-5 
7-9 
Loss of oxygen on 100 pent-] 
oxide J 
\ 8-91 
8-94 
8-97 
9-39 
9-01 
9-00 
Giving a mean loss of 9-03, whereas theory requires a loss of 8 - 75. 
(2) When a current of air 
is passed through acid solutions of the dioxide 
a perma- 
nent blue colour is attained, two atoms of oxygen have been absorbed, and the solution 
contains tetroxide. 
(1) 0-1149 grm. vanadium pentoxide completely reduced by zinc, and the acid 
solution oxidized by a current of air passing through for fifteen hours, required 
9-5 cub. centims. of permanganate solution (1 cub. centim. = 0-001 320 grm. 
oxygen) for complete oxidation. 
(2) 0-0919 grm. vanadium pentoxide, treated in the same way, required 6*3 cub. 
centims. of the permanganate solution for complete oxidation. 
Hence 100 of vanadium dioxide has absorbed (1) 20-9 and (2) 23-4 parts of oxygen; 
in order to pass from the dioxide to the tetroxide 23-78 per cent, is needed. The sul- 
phate obtained by evaporating the blue solution containing this oxide was analyzed by 
Berzelius ( loc . cit. p. 18), and it may be regarded as a vanadyl sulphate, or sulphuric 
acid in which hydrogen is replaced by vanadyl. 
4. Vanadium Pentoxide (Vanadic acid, V 2 0 3 , molec. weight 182-6). — The properties 
mdccclxviii. d 
