Gold selenites

Bakeeva, Pashinkin, Bakeev, and Buketov [73BAK/PAS] measured the selenium dioxide pressure over gold selenite in the interval 489 to 599 K by the dew point method. The pressure was calculated from the dew point temperature by the relationship for the saturated vapour pressure in [69SON/NOV]. The data in the deposited VlNITl document (No. 4959-72) have been recalculated with the relationship selected by the review. The enthalpy and entropy changes obtained from the temperature variation of the equilibrium constant are A //° ((V.123), 544 K) = (576.8 13.0) kJ-mol and A,S° ((V.123), 544 K) = (899.4 + 24.0) J-K -mor. The uncertainties are entered here as twice the standard deviations from the least-squares calculation. 

No experimental data have been found, which would permit a proper calculation of the enthalpy and entropy changes at 298.15 K. Pashinkin and Gospodinov [94PAS/GOS] report (Au2(Se03)3, cr, 298.15 K) = (290.0 28.0) J K mol from an evaluation of the data. The auxiliary data used are not furnished. Bakeeva et al. estimated A C° , to be - 29.3 J-K -mor and assumed that it was constant in the temperature interval in their extrapolation of the data. On this assumption the review obtains Af/7°(Au2(Se03)3, cr, 298.15 K) = -(916.4 15.7) kJ mol and (Au2(Se03)3, cr, 298.15 K) = (273.3 29.0) J-K -mor with selected auxiliary data. The results calculated by the review are not selected due to the uncertainty about the extrapolation procedure. 

The value of the standard enthalpy of formation of gold(lll) selenite reported in [73BAK/PAS] is a misprint. 

No other data for gold selenites have been found. 

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BAK/PAS3] Bakeeva, S. S., Pashinkin, A. S., Bakeev, M. I., Buketov, E. A., Dissociation pressure of gold selenite, Russ. J. Phys. Chem., 47, (1973), 275. From a citation in this Bibliography... 

Reaction of Na2S03 with [Au(OH)4] gives [Au(S03)4]5- and the salt Na5[Au(S03)4]-5H20 has been isolated.51 This contains S-bonded sulfite, and can be reduced by excess sulfite to [Au(S03)2]3-. Selenite complexes of gold(III) are O-bonded, however.525... 

Selenites are likewise reduced to selenium. If, however, the solution of the selenite in concentrated sulphuric acid is treated with sodium sulphite, selenium separates but the tellurite is unaffected the latter can be detected in the solution after eliminating the sulphur dioxide. Salts of silver, copper, gold, and platinum must be absent for they are reduced to the metal by the reagent. 

The thermal dissociation of gold(lll) selenite proceeds by the reaction... 

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