PROFESSOR ROSCOE’S RESEARCHES ON VANADIUM. 
13 
The strength of the permanganate solution, prepared from the pure crystals, was accu- 
rately estimated by iron and oxalic acid ; 1 cub. centim. of standard solution was found 
to be equal to 0-001413 grm. oxygen as a mean of three well-agreeing experiments; the 
strength of this solution, as tested from time to time, was found not to vary during the 
course of the determinations. 
Reduction with Zinc . — 
Exp. 1. Exp. 2. Exp. 3. 
Weight of V 2 0 5 taken 0-1038 0-0963 0-1672 
Cub. centims. permanganate required . 19-4 18-2 31-6 
Loss of oxygen on 100 V 2 0 5 . . . . 26-4 26 - 6 26-6 
The calculated loss of oxygen on 100 vanadium pentoxide, when reduced to the 
dioxide V 2 0 2 , is 26 -3 ; the mean experimental number is 26-53. 
In order to control the foregoing results, a fresh solution of permanganate was pre- 
pared; 1 cub. centim. represented 0-001301 grm. oxygen; 0-1397 grm. vanadium pen- 
toxide dissolved in sulphuric acid and completely reduced by zinc required 27 -7 cub. 
centims. of this solution for complete oxidation, corresponding to a loss of 25 "8 on 100 
parts. In ascertaining the reliability of this method, it was further found that a solution 
containing 0-1 grm. of vanadium pentoxide dissolved in sulphuric acid became of a per- 
manent pink colour on the addition of 0'3 cub. centim. of permanganate solution; also 
that 5 grms. of zinc dissolved in sulphuric acid and diluted to the same strength as in 
the determinations, required only one drop of permanganate solution to produce the 
permanent pink tint. 
Reduction with Cadmium and Sodium Amalgam . — If solutions of vanadium pentoxide 
in sulphuric acid be reduced by cadmium (platinum scraps being added to facilitate the 
evolution of hydrogen), or by an amalgam of sodium, the ultimate result is the formation 
of the lavender-coloured solution of the dioxide. Thus : 
Reduction by Reduction by 
cadmium. sodium amalgam. 
Weight of V 2 0 5 taken 0-0897 0-0681 
Cub. centims. permanganate required (1 = -001413) 16-4 12-8 
Loss of oxygen on 100 V 2 0 5 25*8 26-6 
The mean of these six determinations gives 26-3 as the loss on 100 parts of vanadium 
pentoxide, exactly corresponding to the calculated numbers. 
The salt formed by the reducing action of hydrogen in presence of the above metals 
and sulphuric acid is doubtless a vanadium sulphate, that is, sulphuric acid in which the 
equivalent quantity of hydrogen is replaced by the metal. I have yet to determine the 
composition of these salts. When ammonia or caustic potash is added to the lavender 
solution, a brown-coloured precipitate, probably of vanadium hydroxide, is formed, and 
this instantaneously absorbs oxygen. 
On allowing the neutralized lavender solution to stand exposed to air for a few seconds 
