The Amphoteric Properties of' Tellurium Dioxide

The Oxides and Oxyacids of Tellurium

“…Hot, aqueous solutions of sodium borate and sodium and ammonium fluorides are reported to dissolve tellurium dioxide, but no quantitative data are given (98). Kasarnowsky (72) reports a series of solubility values for various concentrations of hydrochloric acid at 18°, which agree well with the value of the minimum solubility of tellurium dioxide in 1 V HC1 at the isoelectric point of pH 3.8 (64).…”

“…The solubility in water is very slight, about 3 X 10-6 mole/1. at 18° ( 34,64). This is a factor of 10 less than the value of 3.75 X 10-5 mole/1.…”

“…The first and second dissociation constants of tellurous acid were found from conductivity and neutralization curves to be 2.7 X 10~3 and 1.8 X 10~8, respectively (10). Issa and Awad (64) report that tellurium dioxide is amphoteric with an isoelectric point at pH 3.8. Thus tellurous acid has an acid dissociation constant of 1.4-4.3 X 10~6 and a basic dissociation constant of 3.1 X 10-11.…”

The periodic, electrochemical codeposition of cadmium and tellurium

“…The solubility of TeO 2 , which limits the rate of CdTe electrodeposition in aqueous, sulfuric acid solutions, was investigated by Schuhmann {1925), who postulated the species in solution to be HTeO 2 + and electrode reaction ii of Table 1. Issa and Awad (1954) studied the solubility of TeO 2 in aqueous HCl and buffered solutions.…”

“…Because of the low solubility of TeO 2 in aqueous solutions -the maximum concentration of HTeO 2 + is :::::::: 0.001 M (Issa and Awad, 1954) -the Cd 2 + ion concentration may also be chosen to be sufficiently low (:::::::: 0.1 M) so that dilute-solution transport theory (Newman, 1973) can be applied.…”