686 
PROFESSOR ROSCOE’S RESEARCHES ON VANADIUM. 
the peach-coloured trichloride is formed in the anterior portion of the tube, and the 
green crystals of dichloride collect in one spot and are fixed firmly to the glass. If the 
temperature be raised to a bright red heat during the preparation, the dichloride is 
further reduced, a black crystalline powder containing a mixture of lower chlorides 
and metal being produced, whilst the glass tube becomes opaque with formation of the 
silicon-vanadium compound. When heated for a long time in a platinum boat in a 
current of pure and dry hydrogen the dichloride loses all its chlorine, metallic vanadium 
being left in the form of bright greyish-white lustrous metallic grains. The dichloride 
prepared as above, gave the following analytical results : — 
Weight of 
dichloride 
No. taken. 
1. 0*3317 
Silver 
chloride 
found. 
0*7693 
Vanadium 
pentoxide 
found. 
0*2510 
Percentages of 
chlorine. 
57*40 
vanadium. 
42*53 
( 0*2490 
A '\ 0*2462 
0*5876 
— — 
58*37 
— 
— 
0*1832 
— 
41*80 
Hence we have for the composition of the chloride : 
Found. 
A 
V = 51*3 
Calculated. 
41*95 
'(1) 
42*53 
(2) 
41*80 
Mean. 
42*16 
Cl 2 = 71*0 
58*05 
57*40 
58*37 
57*88 
122*3 
100*00 
99*93 
100*17 
100*04 
Vanadium dichloride, when heated in hydrogen or in carbon dioxide, does not volatilize 
without decomposition. It is extremely hygroscopic, instantly absorbing moisture from 
the air, deliquescing to a brown liquid : a portion of this chloride exposed to the air for 
five minutes gained 4 per cent, in weight, and in standing for sixteen hours the increase 
amounted to 50 per cent. When thrown into water the dichloride does not at once 
dissolve, the scales floating on the water without becoming wet ; soon, however, they 
dissolve, forming a violet-coloured liquid identical in tint with the solution of hypo- 
vanadous sulphate obtained by reducing a solution of vanadic acid in sulphuric acid by 
hydrogen evolved from zinc or sodium. Like this latter liquid, the solution of the 
dichloride in water acts as a very powerful reducing agent, bleaching litmus and indigo 
solutions. 
A solution of hypovanadous salt obtained by dissolving 0*2875 grm. of vanadium 
dichloride in water required 8T8 cub. centims. of permanganate solution completely to 
oxidize it (1 cub. centim. =0*00066 grm. oxygen). Hence the percentage (on the 
dichloride) of oxygen needed to oxidize the solution was 18*78, whereas the formula 
2V Cl 2 + 0 3 + 2H 2 O = V 2 0 5 + 4H Cl requires 19*6 per cent. ; the difference between 
the found and calculated numbers is due to the great difficulty of preventing the solu- 
tion absorbing some little oxygen during the analysis, which must of course be con- 
ducted in an atmosphere of carbon dioxide. When the dichloride placed in a platinum 
