16 
PROFESSOR EOSCOE’S RESEARCHES ON VANADIUM. 
Hence 100 parts of vanadium dioxide have absorbed (1) 13‘05 and (2) 12*96 parts of 
oxygen; to pass to trioxide, 11*9 parts are required. 
If a few drops of acid are added to the brown solution, which does not undergo change 
even when air is passed through for several days, it immediately turns green, but does 
not undergo any alteration as regards its oxygen ; thus a brown solution was divided 
into two equal parts, the one which was oxidized whilst neutral and brown required 12*13 
per cent, of oxygen, the other, to which a few drops of hydrochloric acid were added, 
became at once green and required 10*82 per cent, of oxygen to raise it to V 2 0 5 . 
Action of Chlorine upon Vanadium Trioxide . — The action of chlorine upon this oxide 
led Berzelius to give to it the formula VO, (V=68*5) ; but, as has already been stated, 
the fact that one-third of the vanadium remains in combination with oxygen in the 
residual vanadic acid follows equally from the formula V 2 0 3 when V=51*3. 
Thus 3(V 2 0 3 )+6 C1 2 =V 2 0 5 +4 V O Cl 3 . 
Two experiments made in order to test the purity of the trioxide prepared by reduc- 
tion of vanadic acid in hydrogen gave the following results : — 
(1) 4*6004 grms. V 2 0 3 , treated with dry chlorine, gave a residue of 1*8307 grm. V 2 0 5 ; 
theoretically it should yield 1*8597 grm. 
(2) 0*2686 grm. V 2 0 3 yielded 0*992 V 2 0 5 , instead of 1*0858 grm. 
The composition and constitution of the salts forming the green solution still remain 
to be ascertained. 
3. Vanadium Tetroxide , V 2 0 4 = 166*6 (the vanadic oxide of Berzelius). — The 
anhydrous tetroxide was obtained by Berzelius (Pogg. Ann. Bd. xxii. p. 19) by preci- 
pitating the hydrated oxide from a sulphate by sodium carbonate, washing, and igniting 
in vacuo to free it from water. On reducing in hydrogen Berzelius found that 0*762 
grm. yielded 0*691 grm., or 90*67 per cent, of his “suboxide” (V 2 0 3 , V = 51*2) ; and 
hence he legitimately concludes that “ vanadic oxide has lost as much oxygen as the 
suboxide contains, — that is, as much as he thought it contained, for V 2 0 4 yields 90*36 
per cent, of V 2 0 3 : 
V 2 0 2 +0 =V 2 0 3 , 
V 2 0 2 +0 2 =V 2 0 4 . 
The anhydrous tetroxide can also be prepared by the slow oxidation of the black tri- 
oxide at the ordinary atmospheric temperature. It possesses an indigo-blue colour, and 
under the microscope is seen to consist of brilliant blue shining crystals. This remark- 
able change occurs when the black trioxide is exposed for several weeks to the air, and it 
has been repeatedly observed. 1*1686 grm. of the blue crystals thus obtained were 
dried completely under the air-pump, yielded 1*2688 grm. vanadium pentoxide, corre- 
sponding to a percentage increase of 8*57 : 100 parts of the tetroxide require 9*59 parts 
of oxygen for conversion into the pentoxide. These blue crystals are anhydrous. A 
weighed portion of trioxide was exposed to the air and from time to time dried in vacuo 
and weighed. On November 13th, 1866, the weight of the black trioxide was 0*7507 ; 
on February 4th, 1867, the colour had changed to a bluish black, and the weight was 
