Gooch and Ward — Copper Oxalate in Analysis. 457 



Table VI (continued). 

 The Precipitation of Small Amounts of Copper. 







Acetic 



Nitric 









Volume Alcohol 



acid at 



acid at 







Copper 

 taken 



of Oxalic at precip- 

 liquid acid itation 



precip- 

 itation 



precip- 

 itation 



Copper 

 found 



Error 



grm. 



cm 3 . grm. cm 3 . 



cm 3 . 



cm 3 . 



grm. 



grm. 



The effect of precipitation in acetic acid. 

 Volume 50 cn ' 3 : 50 per cent acetic acid. 



0-0010 



50 



2 







25 



_ 



o-ooio 



o-oooo 



0*0020 



50 



2 







25 







0-0021 



-f o-oooi 



0-0031 



50 



2 







25 







0-0027 



— 0-0004* 



0-0041 



50 



2 







25 







0-0041 



o-oooo* 



0-0051 



50 



2 







25 







0-0049 



— 0-0002* 



0-0102 



50 



2 



. 



25 







0-0098 



— 0-0004* 



0-0204 



50 



2 







25 







0-0098 



— 0-0006* 



0-0511 



50 



2 







25 











____f 



o-ooio 



50 



2 







25 



5 



o-ooio 



o-oooo 



0-0020 



50 



2 







25 



5 



0-0021 



+ 0-0001 



0*0031 



50 



2 





25 



5 



0-0033 



+ 0-0002 



0-0041 



50 



2 







25 



5 



0-0042 



+ 0-0001 



0-0051 



'50 



2 







25 



5 



0-0043 



— 0-0002 



0-0102 



50 



2 







25 



5 



0-0103 



+ 0-0001 



0-0204 



50 



2 







25 



5 



0-0204 



+ 00000 



0-0511 



50 



2 







25 



5 



0-0512 



+ 0-0001 







Volume 100 cm3 



50 per 



2ent acetic acid. 





o-ooio 



100 



4 







50 



3 



o-ooio 



o-ooooj 



0-0020 



100 



4 





50 



3 



0-0021 



+ 0-0001 J 



0*0031 



100 



4 





50 



5 



0-0031 



o-oooo 



0-0041 



100 



4 







50 



5 



0-0041 



o-oooo 



0-0051 



100 



4 







50 



5 



0-0051 



+ 00002 



0-0102 



100 



4 







50 



5 



0-0103 



+ 0-0001 



0-0204 



100 



4 







50 



5 



0-0196 



— 0-0008§ 



0-0511 



100 



4 







50 



5 



0-0510 



—o-oooi 







Volume 150 cm 



two-thirds acetic acid. 





o-ooio 



150 



4 







100 







0-0013 



+ 0-0003 



o-ooio 



150 



4 







100 



5 



0-0012 



+ 0-0002 



* Filtration im 



perfect. 





f Filtration 



impossible. 





X Precipitation 



formed 



slowly. 



§ Filtration 



imperfect. 





From these results it appears, first, that by precipitating at 

 a volume of 50 cm3 , freezing, melting, and boiling, the condition 

 of supersaturation may be broken up, the oxalate obtained 

 being soluble in the proportion of about 0-0011 grm. to 50 cm3 

 of liquid ; secondly, that by precipitation at a volume of 50 cm3 , 

 evaporation to dryness, and extraction with the same volume 

 of water, the copper may be recovered to an amount within 



