120 
•f 
c\j 
o 
o» 
o 
10 
Figure 4-4. Effects of dissociation of Ca-EDTA on short term 
cupric ion activity after addition of lO'^M Cu(N 03 ) 2 - 
Note: Background electrolyte 0.5 m KN 03 , pH 8.25 (2 x 10"^M NaHC 03 
bubbled with air), 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 10'^, 10'^ and 10'^M 
Cu(N 03)2 solutions at pH 4:00 in 10'^N KNO 3 background electrolyte. A) 
Calcium (10‘^M) in equilibrium with EDTA prior to copper addition; B) No 
calcium present. 
47 
