364 



Peters — Volumetric Estimation of Copper. 



23 



24 



25 



26 



27 



28 

 29 

 30 



nitric acid in excess. The results show the solubility of copper 

 oxalate in ammonium nitrate and exclude the possibility of 

 such a procedure in this work. 



'Some experiments were made to show the time necessary for 

 the complete precipitation, both in the presence and absence of 

 nitric acid. Following is the record of such work. 



Tarle III (continued). 



CuO 



taken as 



CuS0 4 . 



gms. 



Oxalic 

 acid, 

 gms. 



HN0 3 

 sp. gr. 



1-40. 



cm 3 . 



Yolume 

 at precipita- 

 tion. 

 cm 3 . 

 D 



50 



u 



CuO 

 found, 

 gms. 



Error, 

 gms. 



Details 



of 

 filtration. 



0-1990 

 0-2030 



2-0 

 u 







0-1984 

 0-2025 



— 0-0006 



— 0-0005 



j Filtered hot 

 | immediately 

 j Filtered hot 

 ( immediately 



0-1990 



1-0 







a 



0-1990 



±0-0000 



f Filtered after 

 j cooling ; 

 j stood 15 

 [ minutes 



c< 



u 







E 



0-1987 



— 0-0003 



( Filtered after 

 •j cooling; stood 

 ( 15 minutes 













f Filtered after 



u 



2-0 



5-0 



55 



0-1943 



— 0-0047 



j cooling ; 

 j stood 1 5 

 (^ minutes 



u 

 (< 



u 



K 



a 

 u 



CI 



u 

 u 



u 



0-1969 

 0-1973 

 0-1989 



— 0-0021 



— 0-0017 



—o-oooi 



Stood 2% hours 

 Stood 6 hours 

 Stood 16 hours 



The results in section D would seem to show that a solution 

 containing copper may be precipitated hot as the oxalate and 

 filtered either hot or after cooling with a very slight loss. 

 Tests of the filtrates made with potassium ferro-cyanide con- 

 firmed these results. When nitric acid is present, however, 

 the mixture must stand after the addition of the precipitant. 

 In section E the gradual decrease of the minus error is noticed, 

 as the time of standing is extended, the precipitation being 

 practically complete upon standing over night. 



Separation from Cadmium. 



Bournemann* has used nitric acid for a rough separation of 

 copper from cadmium. This method was tried for a quantita- 

 tive separation in the presence of 6-10 per cent strong nitric 

 acid. The results are found in section F of the table to follow. 



* Loc. cit. 



