424 R. L. Ward — Oxalate- Permanganate Process. 



The experiments .of the second part of the table were per- 

 formed similarly, except that the active mass of the oxalic acid 

 was increased by the addition of more of the crystals before 

 extraction. It will be noticed that when the concentration of 

 the oxalic acid is slight, even the smaller amounts of nitric acid 

 cause considerable errors and that these errors increase with the 

 percentage of nitric acid present. When, however, oxalic acid 

 is added nearly to the saturation point of the liquid, the losses 

 are not large and do not increase materially even when very 

 large quantities of nitric acid are used in the extraction. It is 

 evident, also, that about one milligram of copper goes into 

 solution and the process is only accurate up to this amount. 









Table I. 









The Effect of 



Desiccation and Extraction with Nitric Acid. 



Copper- 

 taken 



Volume 

 at precip- 

 itation 



Volume of 



liquid 



used in 



extraction 



Nitric 

 acid 



Oxalic 

 acid 



Copper 

 found 



Error 



grm. 



cm 3 



cm 3 



cm 3 



grm. 



grm. 



grm. 







Small Amounts of Oxalic Acid 







0-0504 



50 



50 



1 



1 



0-0497 



— 0-0007 



0*0504 



50 



50 



2 



1 



0-0492 



— 0-0012 



0-0504 



50 



50 



3 



1 



0-0487 



— 0-0017 



0-0504 



50 



50 



4 



1 



0-0479 



— 0-0025 



0-0504 



50 



50 



5 



1 



0-0469 



— 0-0035 







Large Amounts of Oxalic Acid. 







0-0504 



50 



50 



3 



6 



0-0495 



— 0-0009 



0-0504 



50 



50 



4 



6 



0-0495 



— 0-0009 



0-0504 



50 



50 



5 



6 



0-0491 



-0-0013 



0-0504 



50 



50 



5 



6 



0-0495 



— 0-0009 



0-0504 



50 



50 



10 



6 



0-0486 



— 0-0018 



0-0504 



50 



50 



15 



6 



0-0486 



— 0-0018 



0-0504 



50 



50 



20 



6 



0-0487 



— 0-0017 



0-0504 



50 



50 



25 



5 



0-0491 



— 0-0013 



0-0504 



50 



50 



25 



5 



0-0491 



— 0-0013 



0-0504 



50 



50 



40 



5 



0-0494 



—o-ooio 



The 



Separation of Cop) 



jer from 



\ Cadmium as Oxalate. 



It was found that the procedure outlined above does not 

 secure a complete separation of copper from cadmium, as some 

 of the latter element is included with the copper and cannot 

 be dissolved even on treatment with concentrated solutions of hot 

 nitric acid. If, however, nitric acid is added before precipita- 

 tion, the oxalate of cadmium separates out only on evaporation, 

 when it readily dissolves on treatment with more acid. 



