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Prof. Roscoe on Vanadium. 



, Apr. 7, 



III. Researches on Vanadium. — Part III. Preliminary Notice. 

 By Henry E. Roscoe, B.A., F.R.S. Received April 7, 1870. 



I. Metallic Vanadium** 



In the second part of " Researches on Vanadium," it -was stated that 

 the metal absorbs hydrogen. This conclusion has been fully borne out by 

 subsequent experiment ; and it appears that the amouut of absorbed or 

 combined hydrogen taken up by the metal varies according to the state of 

 division, first, of the chloride (VCL) 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 aud the metal undergoing oxidation to the lowest oxide, 

 V a O. 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 tetrachloride was 

 prepared in quantity, and from this pure dichloride 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 per- 

 centage 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 atmosphere of hydrogen 

 at a red heat, and is best conducted in strong iron tubes. Explosions occur 

 when sodium acts on the liquid tetrachloride. The substance thus ob- 

 tained 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 hydro- 

 chloric acid, and (2) a heavier grey powder, insoluble in hydrochloric acid, 

 which soon deposits, 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 0 1 . A portion of metal exposed for some weeks to the air 

 also slowly absorbed oxygen, passing into the oxide, V, O. 



II. Vanadium and Bromine. 



1. Vanadium Tribromide, VBr 3 , molec. wt.= 291*3. — When excess of 

 bromine is passed over vanadium mononitride heated to redness, 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 bro- 



* Phil. Trans. 1869, p. 679. 



