Studies of metal carbonate equilibria

The complex-formation equilibria in the system Be11-H2O-CO2(g) have been studied by e.m.f. techniques in 3.0 mol dm-?3 (Na)C104 at 25 0C in the range 2.0 < = log h < = 6.2 where h is the free hydrogen-ion concentration. The total metal concentration, B, has been varied from 1 to 80 mmol dm-?3 and the partial pressure of CO2 from 0.1 to 0.97 atm. The stability constants of the mixed complexes are as follows: log β331 = -8.90 +- 0.02, log β561 = -17.24 +-0.04, log β692 = -29.46 +- 0.06 and log β121 - 10.4 +-0.1. The Raman spectra of concentrated solutions containing the different mixed complexes have been recorded. From these results tentative structures for the mixed hydroxo-carbonato complexes are proposed and discussed. The (1,2,1), (3,3,1), and (5,6,1,) complexes are suggested to possess stoicheiometries BeCO3, [Be3(OH)2(HCO3)]3+, and [Be5(OH)4(CO3)]4+ respectively. (author)