182 WULFENITE. 



solved in hot water ; the small quantity of lead 

 carried into solution is precipitated from the latter, 

 \vhile hot, by a mixture of ammonia and carbonate of 

 ammonia, the solution filtered, acidified with nitric acid, 

 evaporated to dryness, the nitrate of soda extracted 

 from the mass with water, and the molybdic acid tho- 

 roughly washed. 



III. In order to avoid the perforation of the crucible, 

 which occurs frequently in this process, the ore may 

 be fused with an equal weight of carbonized bitartrate 

 of potassa, when the lead separates in the metallic state, 

 without any reduction of molybdic acid taking place. 



IV. The powdered ore is fused with an equal weight 

 of calcined bitartrate of potassa and as much sulphur; 

 the sulphomolybdate of potassa thus produced is dis- 

 solved in water, and the sulphide of molybdenum 

 precipitated from the solution by dilute sulphuric acid. 

 When this precipitate is washed, dried and ignited in 

 a covered crucible, it leaves a crystalline gray sulphide, 

 from which molybdic acid may be prepared by the 

 method employed in treating molybdenite. 



Also by heating the finely pulverized mineral with 

 caustic soda and sulphur, which converts the molybdic 

 acid into a sulphide, which is then precipitated by an 

 acid as MoS 2 . There still remains in solution some 

 molybdenum which may be precipitated by hydro- 

 sulphuric acid. 



V. The finely powdered mineral is digested, with 

 constant stirring, with 1| parts of concentrated sulphuric 

 acid, until it is perfectly white. The heat is then 

 raised to incipient volatilization of sulphuric acid the 

 mixture allowed to cool, and the blue pasty mass stirred 

 up with much water, in order to separate the sulphate 

 of lead ; the solution containing the molybdic acid is 

 decanted, filtered and evaporated in a porcelain dish 

 with addition of some nitric acid, until the sulpu- 

 ric acid begins to evaporate; the mixture should be 



