684 
PROFESSOR ROSCOE’S RESEARCHES ON VANADIUM. 
The calculated percentage gain of oxygen according to the equation 
2VCl 4 + 0 + 4H 2 0 = V 2 0 5 + 8HCl is 4*14. 
The solution of the tetrachloride in water does not bleach litmus-paper ; but if the 
vapours of the boiling tetrachloride are condensed in water, a liquid is obtained which 
contains free chlorine, as it bleaches litmus-paper and liberates iodine from potassium 
iodide. At higher temperatures, as, for instance, when the vapours are led through a 
red-hot tube, much larger quantities of chlorine are evolved. Vanadium tetrachloride 
acts violently upon both dry alcohol and ether, giving in the first case a deep green, and 
in the second a deep red-coloured liquid. I am at present engaged with the examination 
of the products of this action. 
Action of Bromine on Vanadium Tetrachloride . — Vanadium tetrachloride, heated with 
excess of bromine in a sealed tube to 180°, yielded a solid mass, which on drying in a 
stream of carbonic acid at 160°, presented the appearance of the peach-coloured tri- 
chloride, and subsequent analysis proved that this body was formed. It is thus seen 
that, heated in excess of both chlorine and bromine, the tetrachloride splits up into tri- 
chloride and free chlorine, so that vanadium does not readily form a pentad compound 
with the chlorous elements*. 
(2) Vanadium Trichloride , V Cl 3 =157‘8. — The trichloride is a solid body, crystallizing 
in splendid peachblossom-coloured shining tables, closely resembling in appearance the 
crystals of chromium sesquichloride. It is non-volatile when heated in hydrogen, and 
decomposes when heated in the air, red fumes of oxytrichloride being given off in small 
quantity, whilst the solid mass glows with absorption of oxygen, forming the pentoxide. 
Heated in hydrogen it loses, first, one atom of chlorine, forming the dichloride (V Cl 2 ), 
and afterwards, on exposure to a higher temperature, loses the whole of its chlorine, 
metallic vanadium being left as a grey lustrous powder. 
Vanadium trichloride is an extremely hygroscopic substance; it instantly changes 
colour on exposure to moist air, deliquescing to a dark-brown liquid, which on the 
addition of a drop of hydrochloric acid becomes green, containing a solution of vanadium 
trioxide (V 2 0 3 ), or rather of the corresponding hypovanadic salts. 
The trichloride is obtained (1) by the slow decomposition of the tetrachloride at the 
ordinary atmospheric temperatures, (2) by the decompositions of the tetrachloride at its 
boiling-point, ( 3) together with dichloride, when the vapour of the tetrachloride is passed 
mixed with hydrogen through a red-hot tube. Method No. 2 is that which yields the 
trichloride in largest quantity and in the purest state, large quantities of the peach- 
coloured crystals remaining behind in the bulb-retort ; and these only require heating in 
a current of carbon dioxide at 160° in order to yield the pure trichloride. The substance 
* The only other case of an element of a decidedly triad character yielding compounds of a tetrad nature, 
appears to be the nitrosyl-dichloride, NO Cl a , of Gay-Lussac, and the corresponding bromine compound, NO Br a , 
discovered by Landolt. 
