Mr Johnston on Vanadium. 319 



paration of the phosphoric and vanadic acids quantitively from 

 each other is attended with difficulties which I have not yet 

 been able wholly to overcome. The metal, however, may be 

 extracted by the following simple process: The mineral is dis- 

 solved in nitric acid, with which it forms a yellow solution. 

 From this acid solution the lead and arsenic are thrown down 

 by a current of sulphuretted hydrogen. The solution is now 

 of a beautiful blue, and contains the vanadium in the state of 

 oxide. It is filtered and digested for some time in a gentle 

 heat to separate the sulphuretted hydrogen, and a trace of sul- 

 phuret of arsenic remaining in solution. Evaporated to dry- 

 ness by a gentle heat, it changes from blue to green, and 

 leaves a beautiful deep red mass, which is chiefly vanadic acid. 

 This is boiled in successive portions of a perfectly saturated 

 solution of carbonate of ammonia. The colourless liquor is 

 filtered while hot, and deposits on cooling a white crystalline 

 powder in minute prisms, which is a vanadiate of ammonia. 

 This salt may be further purified by again dissolving in dis- 

 tilled water and crystallizing. By exposure to the air it be- 

 comes after some days slightly yellowish, probably from the loss 

 of a portion of ammonia. Heated in the open air, this salt parts 

 with its water and ammonia, and leaves oxide of vanadium, 

 which, by a continuance of the heat, combines with the oxy- 

 gen of the atmosphere, and forms vanadic acid. The yellow 

 powder thus obtained fuses by an increase of temperature into 

 a deep red liquid, and crystallizes on cooling into beautiful 

 prismatic radiating needles, sometimes of a deep red, but ge- 

 nerally of a steel gray colour, and high degree of lustre. Fused 

 in considerable quantity in a covered crucible and cooled gra- 

 dually, it gives beautiful large purplish transparent crysials 

 transmitting a brownish light. These crystals are pure vana- 

 dic acid, mixed when blue or grey with more or less oxide ol 

 vanadium. By heating the salt in close vessels or in an atmo- 

 sphere of carbonic acid, an indigo blue, or, wlien rubbed iii a 

 mortar, a dark olive brown powder i^ obtained, which is the 

 oxide of vanadium. 



II. Metallic Vanadium and it* propen 

 I have not been able to effect thfi reduction of the oxide In 



\i u SERIES, VOL. v- WO H- 0CT0B1 B 1881. \ 



