COLORIMETRIC ESTIMATION OF NICKEL AND COBALT. 417 



If after titrating, the final weights of mixed metals 

 present differ largely from those in the standard neutral 

 solutions, repeat on a fresh portion so that the weight of 

 mixed metals in each solution is approximately the same. 



Example. 

 Weight of Ni + Oo in solution = '022 gm. 



Colour — pink 

 Diluted to 50 cc. 



25 cc. taken = 'Oil gm. Ni + o 



Standard Ni (N0 3 ) 3 solu-^i 



tion added to give [> = 3*7 cc = *037 gm. Ni 



green colour j 



Standard Oo (N0 3 ) 2 solu-^ 



tion required to bring [ .45 cc . = '00135 gm. Oo 

 to standard neutral { & 



tint ) 



Total metals in 50 cc. = '04935 gm. Ni + Oo 



Then 76°/° of '04935 is Ni. 



' 0493 1 5 0Q X 76 = '03751 gm. Ni 

 Ni added = '037 



Ni in the 25 cc. of solution taken — '00051 



2 



50 cc. „ „ = '00102 gm. 



Co + Ni = '022 gm. 

 Ni = '00102 „ 



Oo = '02098 „ 



Probably increase of accuracy would be obtained if a 

 colorimeter were used in which the colours to be compared 

 could be brought into juxtaposition. 



In conclusion I desire to express my warmest thanks to 

 Professor Schofield for pointing out this work and also for 

 the kindly interest he has shown during the course of these 

 experiments. 



Aa— Dec. 7, 1904. 



