COLORIMETRIC ESTIMATION OF NICKEL AND COBALT. 



415 



In the above experiments the solution under examination 

 was compared with a standard containing about the same 

 total weight of nickel and cobalt, selected from a series of 

 various total nickel and cobalt contents, e.g. '03 gm, *04 

 gm, '05 gm, '06 gm, '07 gm in 50 cc, in the proportion of 

 76 + Ni to 24°/° Co. 



The results are more uncertain when the amount of nickel 

 present is as low as If. The large proportion of cobalt 

 necessitates the addition of a correspondingly large amount 

 of Ni before titration ; the amount of metals originally 

 taken must therefore be about '01 gm. (see No. 6 in table) 

 in order that the total weight of metals permissible (about 

 '05 gm.) in 50 cc. of solution is not exceeded. 



The following table gives the results of experiments on 

 solutions containing approximately 99°/° Oo and If Ni. : — 



No. 



Mixed metals 

 taken 



Ni added 

 to give 

 green 

 colour. 



Total 

 Ni + Co 



Co required 



to match 

 standard tint 





Grams 



Grams 



Grams 



Grams 



5 



•05045 









iused 



•025225 



•0895 



•114725 







again 



halved 



•057362 



•C0135 



5a 



•05045 



•0895 



•114725 









halved 



•05736 



•0015 



56 



•05045 









^used 



•01261 



•043 



•05561 



•0015 



6 



•01015 



•034 



•04415 



•000825 



6a 



•01015 



•036 



•04615 



•001125 



7 



•0203 



•078 



•0983 









halved 



•04915 



•00255 



7a 



•0203 



•078 



•0983 









halved 



04915 



•00225 



Total j 

 metals in I 



50 cc. i Taken 



Co 

 •05871 Ni 



Co 

 •05886 Ni 



Co 

 •05711 Ni 



Co 

 •044975 Ni 



Co 

 •047275 Ni 



Co 



•0517 I Ni 



jCo 



•0514 ! Ni 



•04995 



•0005 



•04995 



•0005 



•04995 



•0005 



•01005 



•0001 



•01005 



•0001 



•0201 



•0002 



•0201 



•0002 



Found 



Error 



Grams 



Grams 



•05096 



+ -ooioi 



•00051 



- -00101 



•05048 



+ -0005 



•00003 



- -0005 



•04884 



- -00111 



•00161 



+ -00111 



•00997 



- -00008 



•00018 



+ -00008 



•01022 



+ -00017 



•00007 



- -00017 



•01972 



- -00038 



•00058 



+ -00038 



•02017 



+ '00007 



•00013 



- -00007 



Percent- 

 ige error 

 ou weight 

 of mixed 

 metals 

 taken 



2 

 1 



\ 2 

 \» 



1 -35 



The method finally recommended is as follows : — 

 Solutions required — 

 Standard Ni (N0 3 ) 2 solution containing '01 gm. Ni in 1 cc. 



Co (NO 3 ), 



•003 



Co in 1 cc. 



Standard solutions of neutral tint containing various total 



weights of Ni and Co (in the proportion of 76°/° Ni to 24°/- Co) 

 in 50 cc. e.g., 



