Prof. Koscoe on Vanadium. 63 



that the metal absorbs hydrogen. This conclusion has been fully 

 borne out by subsequent experiment ; and it appears that the amount 

 of absorbed or combined hydrogen taken up by the metal varies ac- 

 cording to the state of division, first, of the chloride (VC1 2 ) from 

 which the metal is prepared, and secondly, and especially, of the 

 metal itself. The metal containing absorbed hydrogen slowly takes 

 up oxygen on exposure to dry air, water being formed and the 

 metal undergoing oxidation to the lowest oxide, V 2 0. At this 

 point the oxidation stops, but in moist air it proceeds still further. 



The difficulty of obtaining metallic vanadium free from admixture 

 of oxide has been again rendered evident. Perfectly pure tetra- 

 chloride was prepared in quantity ; and from this, pure clichloride was 

 made. On heating this to whiteness in dry hydrogen for 48 hours 

 a substance was obtained which gained on oxidation 70*7 per cent* 

 (vanadium requiring 77'79 percentage increase), and therefore still 

 contained a slight admixture of oxide. 



The reducing action of sodium on the solid chlorides was next 

 examined ; in this case the reduction takes place quietly in an atmo- 

 sphere of hydrogen at a red heat, and is best conducted in strong iron 

 tubes. Explosions occur when sodium acts on the liquid tetrachlo- 

 ride. The substance thus obtained was found, after lixiviation, to 

 be free from chlorine, and on washing it separated into two portions 

 — (1) a light and finely divided black powder (trioxide), which 

 remains in suspension, and is soluble in hydrochloric acid, and (2) a 

 heavier grey powder, insoluble in hydrochloric acid, which soon de- 

 posits, and can, by repeated washing, be completely freed from the 

 lighter trioxide. This bright grey powder consists of metallic 

 vanadium, mixed with more or less oxide. If this metallic powder, 

 after drying in vacuo, be reduced at a low red heat in a current of pure 

 hydrogen, it takes fire spontaneously, even when cold, on exposure 

 to air or oxygen, water being formed, whilst the vanadium undergoes 

 oxidation, forming the blue oxide, V 2 4 . A portion of metal exposed 

 for some weeks to the air also slowly absorbed oxygen, passing into 

 the oxide, V 2 0. 



II. Vanadium and Bromine. 



1. Vanadium Tribromide, VBr 3 , molec. wt. = 291'3. — When ex- 

 cess of bromine is passed over vanadium mononitride heated to red- 

 ness, a vivid action occurs, and dense dark-brown vapours are formed, 

 condensing in the cooler portions of the tube to a greyish-black, 

 opaque, amorphous mass of the tribromide. The tribromide is a 

 very unstable compound, losing bromine even when kept sealed up 

 in glass tubes ; it is very deliquescent, and on heating in the air rapidly 

 loses all its bromine and takes up oxygen, with formation of vanadic 

 acid. On being thrown into water, the tribromide readily dissolves, 

 forming a brown liquid (in this respect resembling the trichloride), 

 which, on addition of a few drops of hydrochloric acid, turns of a 

 bright green colour, showing the presence of a solution of an hy- 

 povanadic salt. No free bromine or hydrobromic acid is given off 

 on dissolving the tribromide in water. That a more volatile higher 



