1869.] Dr. H. E. Roscoe's Researches on Vanadium. 



41 



taining oxygen would yield the metal by direct reduction, the author has 

 repeated the experiments of other chemists on this subject, but without 

 success. There is no doubt that the metal cannot be obtained by any 

 of the processes described in the books. The only methods which pro- 

 mised possible results were : — 



1 . The reduction of a vanadium chloride (free from oxygen) in hydro- 

 gen gas, either with or without sodium. 



2. The reduction of the mononitride at a white heat in hydrogen. 



The first of these methods has proved to be successful, whilst the 

 second does not appear to yield metal, inasmuch as the nitride exposed for 

 3 1 hours in a platinum tube to the action of hydrogen at a white heat, 

 lost only 8 per cent., whereas it must lose 21*4 per cent, on conversion 

 into metal. 



Notwithstanding the apparent simplicity of the method, the author has 

 found it exceedingly difficult to obtain the metal perfectly free from oxy- 

 gen. This arises from the fact that whilst vanadium is quite stable at the 

 ordinary temperature, it absorbs oxygen with the greatest avidity at a red 

 heat, and that therefore every trace of air and moisture must be excluded 

 during the reduction. Another difficulty consists in the preparation of the 

 solid chlorides in large quantity and free from oxygen or moisture, as also 

 in the length of time needed to reduce these chlorides in hydogen, during 

 which time unavoidable diffusion occurs and traces of oxygen enter the 

 tube. Again, the reduction can only be effected in platinum boats placed 

 in a porcelain tube, as the metal acts violently on glass and porcelain, and 

 tubes of platinum are porous at a red heat. 



A description of the apparatus employed is then given, the main points 

 being to guard against diffusion, and to introduce the powdered dichloride 

 into the platinum boat in such a way that it shall not for an instant be 

 exposed to moist air. After all precautions are taken the tube is heated to 

 redness, torrents of hydrochloric acid come off, and the evolution of this gas 

 continues for from 40 to 80 hours, according to the quantity of dichloride 

 taken. After the evolution of any trace of hydrochloric acid has ceased to 

 be perceptible, the tube is allowed to cool, and the boat is found to contain 

 a light whitish grey-coloured powder, perfectly free from chlorine. 



Metallic vanadium thus prepared examined under the microscope re- 

 flects light powerfully, and is seen to consist of a brilliant shining crystal- 

 line metallic mass possessing a bright silver-white lustre. Vanadium does 

 not oxidize or even tarnish in the air at the ordinary temperature ; nor 

 does it absorb oxygen when heated in the air to 100°. It does not de- 

 compose water even at 100°, and may be moistened with water and dried 

 in vacuo without gaining weight. The metal is not fusible or volatile 

 at a bright red heat in hydrogen ; the powdered metal thrown into a 

 flame burns with the most brilliant scintillations. Heated quickly in 

 oxygen it burns vividly, forming the pentoxide ; but slowly ignited in air 

 it first glows to form a brown oxide (possibly V 2 0), and then again ab- 



