

Gooch and Ward- 



-Copper 



Oxalate in Analysis. 455 







Table V 









The Effect of Acetic Acid. 







Per cent 











Volume of 



Stronger 



Oxalic 





Copper 



of acetic 



acid 



acid Copper 





taken 



liquid acid 



used 



used found 



Error 



grm. 



cm 3 . 



cm 3 . 

 A 

 in presence 



cm 3 . grm. 



grm. 





Precipitation 



of acetic acid. 





0-0511 



100 25 



.._.' 



2-0 0-0502 



— 0-0009 



0-0511 



100 33 







2-0 0-0504 



— 0-0007 



0-0511 



100 50 







4-0 0-0510 



—o-oooi 



0*1533 



100 50 







4-0 01530 



— 0-0003 





Precipitation in presence of acetic acid and nitric acid. 





0-0511 



105 50 



5 



4-0 0-0510 



— 00001 



0-0511 



110 50 



10 



4-0 0-0506 



— 0-0005 



0-0511 



100 50 



10 



4-0 0-0510 



—o-oooi 



0-1530 



100 50 



10 



4-0 0-1529 



— 0001 



0-1530 



100 50 



10 



4-0 0-1530 



—o-oooo 



Precipitation in presence of acetic acid and sulphuric acid. 



0-0511 100 50 5 2-0 0'0508 —0*0003 



0-0511 100 50 10 2-0 0-0413 — 0'0098 



0-0511 100 50 10 4-0 0-0512' +0*0001 



0-0511 100 50 10 4-0 0-0513 +0'0002 



of 100 cm3 about the same effect as alcohol, and when present to 

 the amount of 50 per cent it diminished still further the solvent 

 power of the medium for the oxalate. The presence of nitric 

 acid to 10 per cent of the entire volume does not materially 

 affect the solubility. Sulphuric acid to 10 per cent of the 

 volume of the liquid is without apparent effect upon the 

 solubility of copper oxalate, provided the oxalic acid is also 

 present in the proportion of 4 grm. to 100 cm3 of the liquid. 

 Treatment by oxalic acid in a medium consisting of acetic acid 

 of half-strength, with or without nitric to the extent of 10 per 

 cent by volume, is plainly the best of the procedures studied 

 for the complete precipitation of copper oxalate in ideal condi 

 tion ; provided, however, that the copper is present in amount 

 sufficient to break up the condition of supersaturation, let us 

 say to the amount of 0'0500 grm. 



The Prevention of Supersaturation. 



Various means have been tried in the effort to break up 

 supersaturation of the precipitating medium with small amounts 



