BERYLLIUM(II) PHOSPHATE COMPLEXES IN AQUEOUS-SOLUTION

The complexation equilibria between Be2+ and phosphate ions have been studied at 25 degrees C in 3 M (Na)ClO4 ionic medium by potentiometric titrations with a glass electrode. [Be(II)] was varied between 5.10(- 4) and 0.03 M, whereas 0.5[Be(II)]less than or equal to[P(V)]less than or equal to 3[Be(II)]. The hydrogen ion concentration ranged from 3 [ Be(II)] to its value at the incipient precipitation of the phosphates, which was [H+] approximate to 10(-3.9) 9 M, for [Be(II)] = 5.10(-4) M , and 10(-2.1) M, for [Be(II)] = 0.03 M. The data have been explained with the formation of species BeH2PO4+, Be(H2PO4)(2)(aq), Be2H-2(H3PO4 )(2+),Be3H-6(H3PO4)(3)(aq), Be3H-8(H3PO4)(6)(2-) and Be3H-5(H3PO4)+ or Be3H-6(H3PO4)(aq). Equilibrium constants with standard deviations are given in Table 1. The effect of medium changes on the consistency of the model with the data is described in some detail.