> 



E 



c 



O 



<v 

 o 



— 

 UJ 



-9 



o 



o 



-10 



12 3 4 



Time (hrs) 

 Figure 4-4. Effects of dissociation of Ca-EDTA on short term 

 cupric ion activity after addition of 10"^-^M Cu(N03)2. 



Note: Background electrolyte 0.5 m KNO3, pH 8.25 (2 x lO'^M NaHC03 

 bubbled with air), 10"'*-2m EDTA, temperature 23°C. A Radiometer 

 selectrode (F 3000), an Orion d/j" reference electrode, and an Orion pH 

 electrode were used. In both experiments, the cupric ion activity (M) was 

 calculated using the Nernst equation and data from lO'**, 10'^ and 10"°M 

 Cu(N03)2 solutions at pH 4:00 in 10"^N KNO3 background electrolyte. A) 

 Calcium (lO'^M) in equilibrium with EDTA prior to copper addition; B) No 

 calcium present. 



47 



