L36 Determination of Copper and Nickel. 



(c) 17 89 gr. of an alloy containing by calculation 4949 



per cent, copper, treated as above, yielded 11-12 gr. 

 CuO + Cu 2 S, equivalent to 8-878 Cu or 49-62 per cent, 

 copper. 



(d) 761 gr. pure metallic nickel, precipitated from its solu- 



tion by hydrosulphuret of ammonium, and treated as 

 above, yielded 9*665 gr. NiO + Ni 2 S, or equivalent to 

 7*607 gr. nickel. 



(e) A solution of 499 gr. nickel and 3*73 gr. copper was 



treated with sulphuretted hydrogen to separate the 

 copper ; the nickel afterwards thrown down by hydro-sul- 

 phuret of ammonium, and both determined as,above, gave 



6-34 gr. NiO + Ni 2 S = 4-98 gr. metallic nickel, 

 and 4-70 gr. CuO + Cu 2 S = 3-75 gr. ... copper. 



As these results appeared extremely satisfactory, it seemed 

 not unlikely that this process could also be extended to 

 the determination of cobalt ; and in consequence, 525 gr. 

 pure metallic cobalt were dissolved in nitric acid, and neu- 

 tralised by ammonia, then precipitated by hydrosulphuret of 

 ammonium. The precipitated sulphuret, after washing, in- 

 cineration, and ignition with carbonate of ammonia, weighed 

 8-98 gr., and even after being several times successively 

 heated with carbonate of ammonia, it weighed 8'68 gr., 

 whereas by calculation it should only have yielded 667 gr. 

 The residue, which was expected to have consisted of oxide 

 and di sulphuret, appeared quite pink, and aggregated to- 

 gether on each ignition, evidently containing a large amount 

 of sulphate of cobalt, which seemed most strongly to resist 

 decomposition, and therefore it does not appear probable that 

 this method could be employed in the determination of cobalt. 



From the results obtained with copper and nickel, it may 

 be concluded that the process here described may safely be 

 used in estimating these two metals ; and, in a very large 

 number of determinations of nickel, it has been found to 

 afford the most accurate and satisfactory results. 



In the case of copper, however, more attention must be 

 paid to the details of the operation, as the protosulphuret of 

 copper, especially in cases where free sulphur has been pre- 



