Copper and Nickel in quantitative analysis. 135 

 which, upon calculation, is equivalent to — 



Copper, 

 Sulphur, . 



Copper, 

 Oxygen, . 



Oxide of copper, 

 Sulphuric acid, 



0-229 

 0058 

 0-287 Cu 2 S 



1-537 

 0-387 



0-029 

 0-030 



1-924 CuO 

 0-059 CuO SO, 



2-270 



or an excess of -03 gr. above the quantities experimen- 

 tally found.* 

 As now the atomic equivalent of sulphur is exactly double 

 that of oxygen, that of the disulphuret of a metal will of 

 course be precisely the same as of its corresponding protoxide ; 

 and this fact consequently enables us at once to calculate the 

 amount of copper or nickel contained in a mixture of the 

 disulphuret and oxide, however variable the relative propor- 

 tions of these compounds may be, and it becomes only neces- 

 sary to remove the small amount of sulphuric acid present in 

 the incinerated sulphurets, in order to determine the amount 

 of the one or other metal present. 



The addition of a small amount of pulverised carbonate of 

 ammonia to the incinerated sulphuret (as soon as cold), and 

 then carefully heating until all ammoniacal salts are expelled, 

 seems completely to effect this object, as will be seen from 

 the following results obtained experimentally : — 



(a) 4-30 gr. metallic copper, precipitated by the electro- 

 type, were dissolved, precipitated by sulphuretted hydro- 

 gen, and treated as above with all precautions. The 

 mixture of CuO + Cu 2 S obtained, amounted to 5*37 

 gr., whereas by calculation it should have been 538 gr. 



(b) 1*76 gr. same copper, similarly treated, yielded 2-21 gr. 



CuO + Cu 2 S, whereas by calculation it should have 

 afforded 2-204 gr. 



* The equivalents for nickel and copper employed in the preceding calcula- 

 tions have been Ni = 2957, Cu == 3166, = 8, S = 16. 



