Thermodynamic data for the solubility of tin(IV) in aqueous cementitious environments

The solubility of Sn(IV) in cementitious systems is directly related to the presence of dissolved Ca. In the presence of typical Ca concentrations, so lid Ca[Sn(OH)(6)] (s) is precipitated, resulting in dissolved tin(IV) conce ntrations that are about four to six orders of magnitude lower than observe d in alkaline, Ca-free systems. From different experiments carried out in i nitially oversaturated and undersaturated solutions, solubility products ha ve been evaluated. A constant of 10(9.85) at I = 0 has been derived for the formation of fresh Ca[Sn(OH)(6)] (precip) according to the reaction Ca2+ + Sn(OH)(6)(2-) doub le left right arrow Ca[Sn(OH)(6)](s). A constant of 10(10.93) has been deri ved in undersaturation experiments for the equilibrium with crystalline Ca[ Sn(OH)(6)] (cr).