340 



On Chemical Tests. 



[Oct. 



off the oxygen of the acid, and of the base, and leaves a metallic sul- 

 phuret. They are all decomposed by charcoal at a red heat, and most 

 of them are thus converted into sulphurets ; carbonic acid, and carbonic 

 oxide being at the same time evolved. 



* 



117. SULPHURETS. It is well known that certain oxides possess 

 the property of precipitating others from their solutions, by combining 

 with the acid of the dissolved oxide ; and this process has been adopted 

 for the separation of certain metallic oxides. 



Metallic sulphurets, prepared in the usual way, may be employed in 

 the same way as the oxides, for precipitating oxides from their solu- 

 tions ; the latter are then converted into sulphurets, whilst the metal 

 of the sulphuret continues in the state of oxide with the acid, previous- 

 ly united with the metal precipitated ; this action of the sulphuret s 

 frequently possesses advantages in chemical analysis. 



The results obtained by employing eight metallic sulphurets will be 

 stated ; they were prepared either by precipitation with sulphuretted 

 hydrogen or an alkaline hydrosulphate. In operating on the solution 

 of a salt by a sulphuret, the sulphuret was always used in excess, 

 and the mixture was exposed to a boiling heat for about a quarter of 

 an hour. 



Sulphuret of lead precipitates nitrate of silver, sesquichloride of iron, 

 nitrate of copper; it does not precipitate nitrate of cobalt, nitrate of 

 cadmium, nitrate of manganese, sulphate of nickel. 



Sulphuret of cobalt precipitates acetate of lead, sesquichloride of iron, 

 sulphate of cadmium, sulphate of copper, nitrate nickel, nitrate of silver ; 

 it does not precipitate sulphate of manganese. 



Sulphuret of iron precipitates nitrate of lead, sulphate of cadmium, 

 sulphate of copper, nitrate of silver; it does not precipitate nitrate of 

 cobalt, sulphate of manganese, nitrate of nickel. 



Sulphuret of cadmium precipitates nitrate of lead, sulphate of copper, 

 nitrate of silver; it does not precipitate nitrate of cobalt, sesquichloride 

 of iron, sulphate of manganese, nitrate of nickel. 



Sulphuret of manganese precipitates acetate of lead, nitrate of cobalt, 

 sesquichloride of iron, sulphate of cadmium, sulphate of copper, nitrate 

 of nickel, nitrate of silver. 



Sulphuret of copper precipitates nitrate of silver ; it does riot preci- 

 pitate acetate of lead, nitrate of cobalt, sesquichloride of iron, sulphate 

 of cadmium, sulphate of manganese, nitrate of nickef. 



Sulphuret of nickel precipitates acetate of lead, sesquichloride of iron, 



