II L. Ward — Oxalate- Permanganate Process. 429 









Table VII. 







The Separation of Copper and Iron by Precipitation in 

 ing Large Amounts of Acetic Acid. 



a Solution Contain- 







Volume 



at 

 precipi- 

 tation 









Copper 

 present 



Iron 

 present 



Oxalic Nitric Acetic 

 acid acid acid 



Copper 

 found 



Error 



grm. 



grm. 



cm 3 



grm. cm 3 cm 3 



grm. 



grm. 



0-0511 



o-ioo 



50 



2 .. 25 



0-0524 



+ 0-0013 



0*0511 



o-ioo 



100 



2 ._ 50 



0-0524 



+ 0-0013 



0-0510 



0-188 



100 



4 _. 50 



0-0514 



+ 0-0004 



0-0510 



0-188 



100 



4 2 50 



0-0511 



+ 0-0001 



0-0510 



0-188 



100 



4 5 50 



0-0499 



-0-0011 



0-0511 



o-ioo 



100 



2 10 50 



0-0475 



— 0-0036 



0-0511 



o-ioo 



100 



4 10 50 



0-0489 



— 00022 



0-0510 



0-188 



100 



4 10 50 



0-0487 



— 0-0023 



0-0510 



0-188 



110 



4 10 50 



0-0468 



— 0-0042 



It appears, however, that when the precipitation is made in 

 a solution just acid with acetic acid and a large excess of this 

 acid is added after cooling to throw out the last traces of 

 copper, the oxalate contains very little iron. The most success- 

 ful procedure is to treat the solution with potassium hydroxide 

 to faint alkalinity, then to make it just acid with acetic 

 acid to precipitate at the boiling temperature with a large 

 excess of oxalic acid. After cooling, about two volumes of 

 acetic acid are added and the oxalate allowed to settle over 

 night. Filtration and titration are made in the usual manner. 

 Results of this procedure are given in Table VIII. 







Table VIII. 









Separation of Copper from Iron by Precipitation in Nearly Neutral Water 

 Solution with Subsequent Addition of Acetic Acid. 



Copper 

 present 



Iron 

 present 



Volume 

 at pre- 

 cipitation 



Oxalic 

 acid 



Acetic 

 acid 

 added 



Copper 

 found 



Error 



grm. 



grm. 



cm 3 



grm. 



cm 3 



grm. 



grm. 



0-0051 



0-31 



50 



6 



100 



0-0049 



— 0-0002 



0-0051 



0-45 



50 



6 



100 



0-0046 



— 0-0005 



0-0543 



0-15 



50 



6 



100 



0-0544 



+ 0-0001 



0*0543 



0-21 



50 



6 



100 



0-0542 



—o-oooi 



0-0543 



0-31 



50 



6 



100 



0-0546 



+ 0-0003 



0-0543 



0-45 



100 



12 



200 



0-0538 



— 0-0005 



0-1629 



0-45 



50 



6 



100 



0-1649 



+ 0-0020 



0*1629 



0-45 



100 



12 



200 



0-1629 



±0-0000 



Should much free acid be present originally it should be 

 removed by evaporation before neutralizing the remainder with 

 the potassium hydroxide ; and if potassium oxalate crystallizes 

 out, as may happen if much potassium salt is present with the 

 large amount of oxalic acid, it is best dissolved in a mixture of 



