414 



E. W. CHALLINOR. 



Reference to the preceding tables of results shows that 

 when the solution was green the errors were as a rule 

 smaller than when it was pink. The reason is obvious, 

 assuming that the change in colour near the neutral point 

 i* equally sharp when equal volumes of either Ni or Co 

 solutions are added. When the Co solution is used only one 

 third of the weight of metal is being added as would be 

 added if the same amount of Ni solutiou were used. 



To further test this, another series of experiments were 

 tried with varying quantities of Ni and Co. A known 

 excess of Ni being added till the solution was pale green, 

 it was then diluted to a definite volume and a portion taken 

 and titrated back with Co solution to the neutral tint. 



The results arc shown in the following table : — 



SERIES I. — Adding known excess of Nickel if necessary. 





1 

 pink 



2 

 pink 



3 

 pink 



4 

 green 



5 

 green 



6 

 pink 





N i added 





( .. added 



T-tal 









Mixed metal* 







t" match 



metiils in 













N i + Co 



standard 



50 cc. 



Given 



Found 



Error 



< 





Drama 



Crams 



Qnuna 



(.mm* 



G ranis 



Grams 



•00484 





•05 



•18 



•23 



11 cc. 





Ni 005 



- -00016 



| taken 







= 0033 



0608 



Co 045 



•01516 



+ -00016 



049 



08 



129 



■s cc. 





Ni 025 



•02534 



+ -0003 



] taken 







= 0024 



03465 



Co -024 



•02366 



- 0003 



0505 



•02 



•0705 



•6 cc. 





Ni -037 



•03632 



- -00068 









= 0018 



03705 



Co 0135 



•01418 



+ -00068 



05 





05 



'2 (i DC. 





Ni 0495 



04985 



+ -0003 



\ taken 







= -0078 



•0328 



Co 0005 



00015 



- -0003 



0221 





•0221 



1*4 cc. 



0263 



Ni 02 



•02001 



+ -ooooi 









s= -0042 





Co 0021 



•00209 



- -ooooi 



•041 



055 



096 



•45 cc 





Ni 02 



02001 



+ -ooooi 



taken 







•00135 



04935 



Co -021 



02099 



- -ooooi 



Percent- 

 age error 

 on weight 

 of mixed 

 metals 



}« 



1-35 

 •6 

 •05 

 •02 



Maximum error (No. 3) 'OUU68 gm, in "0505 gm. = 1'3% 

 SERIES II.— Adding known excess of Nickel. 



Colour. 



Mixed mettle 



taken 



1 



pink 



2 



pink 



3 

 pink ; 



4 I 

 pink 1 



031 



^ taken 



•022 



| taken 



the other 



half 



•01715 



o taken 



the other 



half 



•02555 



.V taken 



the other 



half 



Ni added Co required 



1 to match 



green Ni t Co standard tiut 

 colour. 



Grams 



Grams 



Grams 



•045 

 •037 

 •034 

 •033 

 •044 

 •05 



•101 



•0505 -0021 



•056 -0039 



•048 ! "00135 



•04257 -00255 



•04157 '0021 



•05677 '00158 



•06277 -00345 



Total 



metals in 



50 cc. 



0526 



0599 



04935 



04513 



04367 



05835 



06622 



Grams 



0o-021 

 Ni'01 

 Co -021 

 XiiOOl 

 Co -021 

 Ni -001 

 C.-01665 

 Ni -0005 



o -01665 

 Ni-0005 

 Co -02505 

 Ni'0005 



'o -02505 

 N T i -0005 



Grams 



•02105 



•00995 



•02095 



•00105 



•02099 



•00101' + 



-01656 I - 



•00059 + 



•01675 | + 



•00396 



•02486 



•00069 



0249 



•00065 



•00005 

 •00005 

 •00005 

 ■00005 



•ooooi 



•00001 

 •00009 

 •00009 

 •00014 

 •00014 

 •00019 

 •00019 

 •00015 

 •00015 



Percent- 

 ige error 

 on weight 

 of mixed 

 metals 

 taken 



!• 



10 



f 



•23 



•05 



•53 



Maximum error (No. 3) -00014 gm. in '01715 gm. = -8%. 



