PROFESSOR ROSCOE’S RESEARCHES ON VANADIUM. 
681 
ness, the distillate possesses a port-wine colour, and it is only by frequent rectifications 
over sodium that the canary-yellow colour of the pure oxychloride is obtained. This 
coloration, though ascribed by Schafarik to the presence of traces of vanadic acid, is 
really due, as I have formerly pointed out, to the presence of a dark-coloured vanadium 
chloride produced in the reaction and decomposed on rectification over sodium. This 
observation, coupled with the fact already made use of to demonstrate the existence of 
oxygen in the oxytrichloride, viz. that this substance yields up oxygen to red-hot char- 
coal, points the way to the second method for the preparation of the tetrachloride. 
This consists in passing the vapour of the oxytrichloride, together with an excess of 
dry chlorine, slowly over a long column of pure sugar-charcoal heated to dull redness. 
This operation has to be repeated four or five times before the last traces of oxygen are 
withdrawn. Even after one distillation the product attains a dark reddish-brown tint, 
and boils at 152° ; but it still contains 1 per cent, of oxygen, and needs three or four very 
slow repetitions of the process in order to obtain it perfectly pure. The solid trichlo- 
ride is always found in the bulb from which the tetrachloride is distilled ; but this, if 
carefully heated, slowly burns away in the excess of chlorine. 
The portions of substance used for analyses 1, 2, and 3 were prepared from nitride, 
those in Nos. 4, 5, and 6 were obtained directly from the oxytrichloride. The chloride 
in analysis 4 was distilled three times over charcoal, and still contained a little oxygen ; 
after another distillation (analysis 5) the oxygen was reduced to 02 per cent., and after a 
fifth distillation (analysis 6) the whole of the oxygen had been removed. The determi- 
nations were made by breaking a bulb containing a weighed quantity of substance in a 
closely stoppered bottle containing water ; the chlorine was then estimated as silver-salt, 
nitric acid being added after the nitrate of silver, whilst the vanadium, either in the 
filtrate or in another portion of chloride, was weighed as pentoxide. 
Percentages 
Weight of tetra- 
chloride found. 
Silver chloride 
found. 
Vanadium pentoxide 
found. 
f 
of chlorine. 
-A. 
A 
of vanadium. 
0-4272 
1-2555 
— 
72-68 
— 
0-6645 
— 
0-3195 

27-02 
0-9644 
2-8560 
— 
73-24 
— 
1-0362 
— 
0-4890 
— 
26-52 
1-0438 
3-0441 
— 
72-14 
— 
0-9875 
— 
0-4632 
— 
26-36 
0-8935 
2-6266 
— 
72-73 
— 
1-1465 
— 
0-5440 
— 
26-65 
0-2940 
0-8667 
— 
72-95 
— 
0-4950 
1-5760 
0-2370 
72-83 
26-89 
0-4080 
1-2086 
0-1960 
73-28 
27-05 
