COLORIMETRIC ESTIMATION OF NICKEL AND COBALT. 



Aqueous 



HN0 3 





Solution. 



Solution. 



Result. 



H 2 added 



HN0 3 added 





20 CC. 



20 cc. water 



identical tints 



1 



1 CC.HNO3 



no apparent difference 



2 



2 



ditto 



3 



3 





ditto 



4 



4 



u 



ditto 



5 



5 





P 



6 



6 





a doubtful difference 



7 



7 



> 



a very faint pinkish tint 



8 



8 



, 



more pronounced pinkish tint 



9 



9 



„ 



a faint pink 



10 



10 



t 



ditto, more marked 



15 



15 



, 



faint pink still more markpd 



Prom these results it appears that the presence of more 

 than 5 cc. strong HNOs in the solution would have a decided 

 influence on the estimation. 



The next series of experiments were carried out under 

 conditions similar to those which would be used in actual 

 practice. 



The given nitrate solutions were evaporated over water- 

 bath with concentrated H 3 S0 4 to get rid of HN0 3 diluted 

 with water, (NHi) 2 S0 4 and excess of NH^OH added, and 

 solution electrolysed under usual conditions without any 

 particular care, since the method used is only an approxi- 

 mate one. The precipitated metals were dissolved in HNO 3 

 evaporated to pastiness, diluted to definite bulk and a pro- 

 portion taken for estimation. The following table shows 

 the results : — 





Mixed Metals 



Colour 



Ni or Co added 



Total 



metals iu 



50 cc. 



grams 



Given 



Found 



Error 



Percent- 

 age error 



2 



Given 



Deposited by 

 ■Electrolysis 



cc. 



Grams 



on weight 



of mixed 



metals 



1 



2 

 3 

 4 

 5 



•1010 



£ taken 



•1185 



| taken 



•1010 



£ taken 



•1000 



| taken 



•072 



\ takpn 



•1001 



•1176 



•1006 

 •0996 

 •072 



pink 

 drab 

 pink 

 green 

 green 



2-75 



diluted 

 matched 



2-925 



1-95 

 1-15 



•0275 Ni 



to 50 cc. this 

 standard. 



•02925 Ni 



•00585 Co 

 •00345 Co 



•05253 



•0588 



•0544 



•05565 

 •03945 



Ni -050 

 Co -051 

 Ni-09 

 Co -0285 

 Ni -050 

 Co -051 

 Ni -085 

 Co -015 

 Ni -06 

 Co -012 



•04967 

 •05043 

 •08938 

 •02822 

 •04838 

 •05222 

 •08459 

 •01501 

 •05996 

 •01204 



- -0003 



- -00057 

 + -00062 



- -00028 



- -00162 

 + -00122 



- -0004 



+ -ooooi 



- -00004 

 + -00004 



•3 



y -56 



•5 



1-6 



yv2 



•4 



j-01 



J -05 



Maximum error (No. 3) -00162 gm. in -101 gm. 



16% 



