40 Dr. H. E. Roscoe's Researches on Vanadium, [June 17, 



The trichloride is extremely hygroscopic, deliquescing on exposure to air to 

 a brown liquid. The trichloride is best prepared by the quick decomposi- 

 tion of the tetrachloride at its boiling point, or by its slow decomposition 

 at the ordinary temperature of the air. The crystalline powder obtained 

 by either of these methods only requires freeing from adhering tetrachlo- 

 ride by drying in carbon dioxide at 1 60° in order to yield good analytical 

 results. 



Calculated. Mean of 4 analyses, 



V = 51*3 32-5 32-57 



Cl 3 = 106-5 67*5 67-42 



157-8 100-0 99-99 



The trichloride thrown into water does not at once dissolve; but, as soon 

 as the crystals get moistened, a brown solution is formed, which becomes 

 green on addition of a drop of hydrochloric acid, and contains a hypova- 

 nadic salt in solution. This green tint is identical with that got by re- 

 ducing a solution of vanadic acid in presence of magnesium. According to 

 the equation 2VC1 3 + 0 2 -f 3H 2 0=V 2 0 6 -f 6HC1 the solution of the tri- 

 chloride requires 10" 14 per cent, of oxygen to bring it up to vanadic acid, 

 whilst analysis showed that 10*1 per cent, was necessary. The specific 

 gravity of the trichloride at 18° is 3*00. 



3. Vanadium Bichloride VC1 2 = 122*3. — The dichloride is a solid cry- 

 stallizing in fine bright apple-green micacious plates. It is prepared by 

 passing the vapour of vanadium tetrachloride mixed with hydrogen 

 through a glass tube heated to dull redness. If the heat be pushed 

 further a blackish crystalline powder, consisting of a mixture of lower 

 chloride and metal, is obtained. The dichloride, when strongly heated in 

 hydrogen, loses all its chlorine, leaving vanadium in the metallic state in 

 grey crystalline grains. Analysis gave : — 



Calculated. Mean of 2 analyses. 



VC1= 51*3 41*95 42*16 



Cl 2 = 71*0 58*05 57*88 



122*3 100-00 100-00 



Vanadium dichloride is extremely hygroscopic ; when thrown into 

 water a violet-coloured solution is formed, identical in tint with the liquid 

 containing a hypovanadous salt obtained by reducing vanadic acid in solu- 

 tion in presence of zinc- or sodium -amalgam ; and like this latter liquid, 

 the solution of dichloride in water bleaches strongly by reduction. 



Oxidized by permanganate this liquid required 18*78 percent, of oxygen 

 (on the dichloride taken) to bring it up to vanadic acid, whereas the equa- 

 tion 2VCl 2 +0 3 + 2H 2 0=V 2 0 5 + 4HC1 requires 19*6 per cent. The spe- 

 cific gravity of vanadium dichloride at 18° is 3'23. 



Metallic Vanadium V = 51*3. — Although from what we now know of 

 the characters of vanadium it appeared unlikely that any compound con- 



