Table 9.

Calcium ion association constants to various anions (Hawley 1973; Martell and Smith 1974) for the formation of ion complexes at the listed ionic strengths and adjusted to the ionic strength of the extraction (calculated by Eq. 5)

	Citric	Carbonica	Oxalicb	Succinic	Hydroxide	Acetic	Chloric
Ion valency	−3	−2	−2	−2	−1	−1	−1
Log Ca2+ association constant in the literature reference	3.45	2.21	2.46	1.25	1.0	0.57	−0.14
Ionic strength in the literature reference	0.1	0.72c	0.1	0.1	0.1	0.1	1c
Ionic strength at extraction	0.6c	0.45	0.45	0.45	0.3	0.3	0.3
Log Ca2+ association constant at ionic strength of extraction	2.72	2.28	2.03	0.82	0.83	0.40	−0.06

^aNo association constant in proximity to the ionic strength at extraction was found for the carbonate ion in Martell, and Smith critical stability constants, and thus, a value from another publication was used

^bValue obtained at 37 °C instead of 25 °C as for all other values

^cThe Davies equation, used for the calculation of the calcium ion association constant at the ionic strength of the extraction, is developed for ionic strengths below 0.5 but can be used above with less reliability