CHROMTTE. 187 



101. VANADINITE. (VANADATE OF LEAD.) 

 PbCl, + 3(3PbO,V0 3 ). 



There exist some varieties of this mineral, at 

 present very rare, which contain no chloride of lead. 



This mineral, when treated with nitric acid, first 

 becomes red, then dissolves. If the solution be mixed 

 with ammonia, and afterwards with an excess of 

 sulphide of ammonium, sulphide of lead is precipitated, 

 and a dark red solution obtained, from which acids 

 precipitate the dark brown sulphide of vanadium. The 

 precipitate is' roasted in air, and afterwards converted 

 into vanadate of potassa by fusion with a small 

 quantity of nitre. This salt is dissolved in a little 

 water, and vanadate of ammonia precipitated from the 

 solution by sal-ammoniac. (See No. 100.) 



The mineral is only imperfectly decomposed by 

 sulphuric acid. The decomposition, however, is com- 

 plete if it be fused with bisulphate of potassa. On 

 treating the mass with^water, the lead remains behind 

 as sulphate, while vanadic acid is dissolved. 



Or the mineral may be decomposed by a mixture of 

 concentrated hydrochloric acid and alcohol, the chloride 

 of lead is washed with alcohol, and the excess of acid 

 evaporated from the blue solution of chloride of vana- 

 dium. This solution is treated with an excess of 

 caustic soda, and the oxide of vanadium is converted 

 into vanadic acid by a current of chlorine gas. 



102. CHROMITE. (CHROME-IRON-ORE.) 

 FeO, Cr 2 O 3 . 



I. For the mere qualitative separation, the very fine- 

 ly powdered ore is fused for at least half an hour, at 



