Yttrium selenites

Additional data for hydrogenselenites and oxide selenites were found in Section 29.3.4 and 29.3.5, on pp. 428 and 431, respectively. 

Precipitation from Aqueous Yttrium Selenite Systems 

The microscopically heterogeneous compound is obtained by mixing aqueous solutions of YCI3 and Na2Se03. It becomes crystalline by heating to 490°C (= crystallization temperature) [3]. The formation of a hydrate by reaction of YCI3 and Na2Se03 in aqueous solution at 25°C is also reported by [1]. It is insoluble and partly hydrolyzes. 

Gospodinov and Stancheva [94GOS/STA] investigated the system Y203-Se02-H20 at 

15 K by solubility measurements over the interval 0 to 85 mass-% of selenious acid in the liquid phase. Solids of composition Y2(Se03)j-4H20 and Y2(Se03)3-H2Se03-5H20 were identified in the phase diagram from the tie lines and by chemical and X-ray analysis. The primary solubility data are available. 

Suponitskii, and Karapet yants [68MAI/SUP] prepared crystalline Y2(Se03)3 and made a calorimetric determination of its enthalpy of dissolution in HCl(aq, 1 18.5). The review has recalculated the data and obtains Af //° (Y2(Se03)3, cr, 

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Crystalline yttrium selenite was prepared and its enthalpy of dissolution in the solvent HCl(aq, 1 18.5), denoted sin, as well as the enthalpy of dissolution of selenious acid in the same solvent were determined. The enthalpy of dissolution in the medium of yttrium chloride, which is needed as an auxiliary datum, was not measured. The review has therefore estimated the enthalpy change of Reaction 3 in Table A-63 from dissolution data of YCl3(cr) in HCl(aq) in [88X1A/ZHU] and [970PP/EHR]. The evaluation also uses the mean value of the enthalpy of formation of YCl3(cr) in these references. 

MAI/SUP] Maier, A. I., Suponitskii, Y. L., Karapet yants, M. K., Enthalpy of formation of scandium and yttrium selenites, Izv. Akad. Nauk SSSR, Neorg. Mater., 4, (1968), 921-924, in Russian, English translation in [68MAI/SUP2]. Cited on pages 354, 356, 498, 522, 528. 

Precipitation from Aqueous Yttrium Selenite Systems... 

Ternary rare earth selenites are also known, although the number of studies on them is still very limited. Giesbrecht and Giolito (1967) reported the precipitation of amorphous sodium yttrium selenite NaY(SeOj)2-3H20 by mixing yttrium chloride and sodium selenite solutions. A systematic study of the formation of the sodium, potassium, and ammonium compounds was carried out by Erametsa et al. (1973). Besides the composition of the MR(Se03)2 H20 (M = Na, K, or NH4 n = 2 or 2 ) phases they recorded the X-ray powder diffraction patterns for the different structural types and studied the compounds by IR spectroscopic and thermoanalytical techniques. A detailed study on the formation of scandium... 

The double alkali sulfates are used in separating tho yttrium and cent groups. The ethyl sulfates are very useful in certain separations, but th are rather difficult to form and they must be handled very carefully becai they decompose easily, even at room temperature. Sulfites, thiosulfat dithionates, selenites, and selenates of most of tho metals have been p pared. 

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