Cerium Selenates

Data for Ce2(Se04)3 and additional data for Ce2(Se04)3-nH20 are found in Section 29.4.1 and 29.4.2, on pp. 453 and 454, respectively. 

The electrical conductivity of an aqueous 1.25x10 M 002(8004)3 solution Indicates the existence of five ions in solution, Gomez Madrazo et al. [1]. 

The compound was prepared from Ce(OH)4 and hot H2Se04. The insoluble product was filtered and washed with alcohol. X-ray powder diffraction patterns (interplanar spacings and line intensities are tabulated) show it to be orthorhombic, isomorphous with Zr(Se04)2-4H20 and the sulfates, space group Fddd-D (No. 70) with a = 27.31 0.02, b = 12.38 0.01, c = 5.736 0.006 A V = 1940 A, Z = 8. Measured and calculated density 3.47 and 3.41 g/cm, Nabar, Ajgaonkar [3]. 

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A number of ionic compounds decrease in solubility with increasing temperature. Calcium sulfate, CaS04, and calcium hydroxide, Ca(OH)2, are common examples. They are slightly soluble compounds that become even less soluble at higher temperatures. Cerium selenate, Ce2(Se04)3, shown in Figure 12.11, is very soluble at 0°C but much less soluble at 100°C. 

A. Benoit, J. X. Boucherle, J. Flouquet, F. Holtzberg, J. Schwelzer, C. Vettier, Thulium Selen-ide and Cerium Compounds Properties, Valence Fluctuations Solids St. Barbara Inst. Theor. Phys. Conf., Santa Barbara, Calif., 1981, pp. 197/207. 

For the element ceritrm, the mixed valent acidic selenate (H30)Ce2(Se04)4 has been described (Iskhakova and Tursina, 1989). The assignment of the different oxidation states of cerium can be done by irrspection of the Ce-0 distances. Both species, Ce + and Ce", are eightfold eoordinated by oxygen atoms. The distances for Ce + range from 2.41 to 2.55 A while the respective values for Ce + are foimd to lie between 2.25 and 2.41 A. In the three-... 

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