The incomplete dissociation of thallous hydroxide

Abstract

The thallous ion and silver ions are unique among univalent cations in forming fairly strong complexes with univalent anions. A review of previous evidence (involving measurements of solubilities, conductivities and reaction kinetics) indicates that thallous hydroxide is incompletely dissociated, having a thermodynamic dissociation constant of about 0.15. New data are reported on the effect of thallous ions on the velocity of the fast reaction between nitroethane and hydroxyl ions. These lead to a similar value for the dissociation constant if it is assumed that the species TIOH does not react. Measurements have also been made of the ultra-violet absorption of solutions containing thallous and hydroxide ions. The results show clearly the presence of two distinct absorbing species, and although it is not possible to derive unambiguously a dissociation constant for TIOH, the data are consistent with the value given above. The nature of the binding in TIOH is discussed in the light of the above findings.