Peters — Volumetric Estimation of Copper. 



363 



Table III (continued). 





CuO 





HN0 3 



Volume 









taken as 



Oxalic 



sp. gr. 



at precipi- 



CuO 







GuS0 4 . 



acid. 



1-40. 



tation. 



found. 



Error. 





gms. 



gms. 



cm 3 . 

 B 

 5-0 



cm 3 . 



gms. 



gms. 



10 



0-1860 



0-5 



55 



0-1859 



—o-oooi 



11 



« 



« 



u 



it 



0-1860 



±0-0000 



12 



0-1990 



2-0 



a 



a 



0-1989 



— 00001 



13 



u 



3-0 



a 



a 



0-1990 



±0-0000 



14 



a 



2-0 



10-0 



60 



0-1971 



-0-0019 



15 



a 



3-0 



a 



a 



0-1987 



— 0-0003 



16 



<( 



(C 



C'C 



tt 



0-1985 



— 0-0005 



17 



a 



5-0 



12-0 



130 



0-1977 



— 0-0013 



18 



a 



C( 



a 



cc 



0-1975 



— 0-0015 



19 



a 



<( 



25-0 



it 



0-1837 



— 0-0153 



20 



K 



c« 



a 



cc 



0-1831 



— 0-0159 



21 



it 



c. 



5-0 



(C 



0-1983 



— 0-0007 



22 



u 



a 



a 



a 



0-1988 



— 0-0002 



23 



a 



2-5 



C 

 5-0* 



65 



0-1971 



— 0-0029 



24 



a 



2-0 



it 



« 



0-1981 



— 0-0019 



the copper does come down completely in the presence of the 

 large amount of the nitric acid upon the addition of more 

 oxalic acid, as seen in experiments 15 and 16. In experiments 

 17 and 18 with a larger volume of water and a larger absolute 

 amount, though approximately the same percentage, of nitric 

 acid present as in experiments 10-13, there is a slight loss of 

 copper; but in experiments 21 and 22 when the amount of 

 nitric acid is reduced to 5 cm3 in the larger total volume the 

 results are normal. Experiments 19 and 20 show the increased 

 loss when still larger amounts of nitric are present. These 

 facts would make it seem best to limit the absolute amount of 

 nitric in solution to about 5 cm3 . 



One observation may well be noted here ; namely, that while 

 one-half gram oxalic acid is all that is needed for the complete 

 precipitation of the copper in the presence of 5 cm3 strong nitric 

 acid, still the oxalic acid may be added up to the point of satu- 

 ration of the solution. More than this causes difficulty owing 

 to the fact that a large amount of water is necessary to wash 

 the precipitated oxalate. About 2 # gms. of oxalic acid to 

 50 cm3 of water is a convenient proportion. 



In experiments 23 and 24, 5 cm3 of nitric acid were neutral- 

 ized with ammonium hydroxide before adding the 5 cmS strong 



* About 9 gms. of ammonium nitrate present in addition to the 5 cm3 of nitric 

 acid. 



