Table 1.

Determination of pK_s0 for Mg and Ca phytates^a

Cation	H+ added (μmol)	[M2+]tot (mM)	[InsP6]tot (mM)	[H+]tot (mM)	[M2+]free (M)	[H2L10−]free (M)	pKs0
Mg	4.89	0.781	0.156	0.556	4.01 × 10−4	1.29 × 10−16	32.87
	19.6	1.84	0.369	1.71	1.28 × 10−3	3.41 × 10−19	32.93
	19.6	1.83	0.366	1.70	1.28 × 10−3	3.32 × 10−19	32.95
	19.6	1.83	0.366	1.70	1.28 × 10−3	3.32 × 10−19	32.95
Ca	193.7	9.83	1.97	15.3	7.88 × 10−3	2.22 × 10−29	39.2
	193.7	9.48	1.90	15.2	7.61 × 10−3	1.57 × 10−29	39.4
	193.7	10.0	2.00	15.4	8.02 × 10−3	2.43 × 10−29	39.1
	193.7	9.31	1.86	15.1	7.48 × 10−3	1.35 × 10−29	39.5
	193.7	9.95	1.99	15.4	7.98 × 10−3	2.27 × 10−29	39.1
	193.7	9.38	1.88	15.2	7.53 × 10−3	1.39 × 10−29	39.5

^a“H⁺ added” represents the amount of protons in the volume of acid added at the start of the saturation runs. [M²⁺]_tot is the total concentration of Mg or Ca determined in the saturated solution. [InsP₆]_tot corresponds to 1/5 the amount of M²⁺, while [H⁺]_tot is calculated as [H⁺]_added plus two times the total amount of InsP₆, both according to the stoichiometry of the solid phytates previously determined. [M²⁺]_free and [H₂L¹⁰⁻]_free correspond to free equilibrium concentrations calculated using HySS software. The pK_s0 values are valid for I = 0.15 M NaClO₄ and 37 °C.