82 BOURNONITE. 



weighed bulb-tube, and heated in a stream of hydrogen 

 gas, at first very gently, and ultimately to the fusing 

 point of the antimony,, from which the sulphur is thus 

 completely separated. 



Or, instead of the hydrogen, a stream of carbonic acid 

 gas free from air may be passed through the tube, and 

 the precipitate heated in it until it does not lose any 

 more sulphur, and is converted into black tersulphide 

 of antimony. 



A more accurate method consists in converting the 

 sulphide of antimony into the antimoniate of the oxide 

 of antimony (Sb 2 O 3 , Sb 2 5 ), complete oxidation being 

 produced by fuming nitric acid. To prevent too rapid 

 action it should be moistened first with a few drops of 

 weak acid. 



The oxidation is made in a weighed porcelain cru- 

 cible. By digesting for some time the decomposition 

 is complete, and the pulverulent precipitate of sulphur 

 separates. The acid is then carefully evaporated and 

 the residue ignited. 



56. BOURNONITE. 

 8 Cu 2 S, Sb a S 3 + 2 (3 PbS, 



The powdered mineral is gradually and carefully 

 oxidized with concentrated nitric acid, the mass mixed 

 with ammonia, and digested for some time, in a closed 

 vessel, with yellow sulphide of ammonium. The so- 

 lution is then treated as directed in No. 55. 



The residue containing sulphide of copper and sul- 

 phide of lead is dried in the funnel, detached as far as 

 possible, from the filter, the latter incinerated, and the 

 sulphides afterwards oxidized, in a dish, by the gradual 

 addition of fuming nitric acid. Some sulphuric acid 

 is then added, the whole of the nitric acid expelled by 



