4:54 Gooch and Ward — Copper Oxalate in Analysis, 







Table IV. 







The Effect of Alcohol. 



Copper 

 taken 



Volume 



of 

 liquid 



Per cent 



of 

 alcohol Oxalic Nitric 



in acid acid Copper 

 liquid used present found 



grm. 



Error 



Precipitation in absence of nitric acid. 



0502 



100 



20 



1-0 







0-0492 



—o-ooio 



0*0502 



100 



20 



2-0 







0-0491 



— 0-0011 



0-0502 



100 



40 



2-0 







0-0491 



— o-ooii 



0-0502 



50 



50 



2-0 







00499 



— 0-0003 



0-0202 



50 



50 



2-0 







0-0499 



-0-000.3 







Nitric acid 



B 

 present 



in the liquid. 





0-0502 



100 



20 



1-0 



5 



0-0493 



— 0-0009 



0-0502 



100 



20 



2-0 



5 



0-0491 



—o-ooii 



0-0502 



100 



40 



4-0 



5 



0-0497 



— 0-0005 



0-0502 



50 



40 



2-0 



2 



0-0497 



— 0-0005 



solution is to prevent the formation of a basic salt, it would 

 seem that the alcohol not only makes the precipitate more 

 insoluble but checks hydrolytic action as well. In a volume 

 of 100 cm3 containing 20 per cent of alcohol the error approxi- 

 mates— 0-0010 grm. ; and for a volume of 50 cm3 containing 50 

 per cent alcohol the error is still negative though reduced to 

 — 0*0003. The effect of nitric acid accompanying the alcohol 

 is not marked. 



In further experiments it was found that the addition of 

 acetic acid, as proposed by Classen,* is even more effective 

 than the use of alcohol, or of alcohol with nitric acid. In 

 Table V are given the details of experiments in which the 

 precipitation of copper oxalate was made in presence of con- 

 siderable amounts of acetic acid. When considerable amounts 

 of copper are present the precipitates formed in solutions con- 

 taining acetic acid are apt to be very finely divided and conse- 

 quently difficult to filter. A better condition of the precipitate 

 is obtained, however, if, with the acetic acid, there is also 

 present a moderate amount of nitric acid. The results of 

 experiments in which both acetic acid and nitric acid were 

 used are given in the table. The results of experiments in 

 which sulphuric acid was present with acetic acid are also 

 appended. 



From these results it is apparent that acetic acid when present 

 to the amount of 25 per cent of the liquid produces in volumes 



*Ber. Dtsch. Chem. Gesellsch., x. b, 1316. 



