engleski

Calcium Hydrogenurate Hydrates Formed via Ca(C_5H_3N_4O_3)2L_3 Complexes, L=(CH_3)_2SO, (CH_3)_2NCHO

Oxygen donor complexes  1 of calcium hydrogenurate of the composition Ca(C_5H_3N_4O_3)_2L_3, L=(CH_3)_2SO, (CH_3)_2NCHO, if exposed to moist atmosphere, shortly washed with water or organic solvents containing small amount of water were transformed to hydrates Ca(C_5H_3N_4O_3)2 nH_2O, n=2, 3. The X-ray powder diffractograms as well as the thermogravimetric decomposition curves indicated distinct difference between dihydrate and trihydrate. Yet, thermally and structurally the trihydrate was more stable than dihydrate and the latter if exposed to moist atmosphere slowly transformed to trihydrate. If suspended in water the dihydrate and trihydrate recrystallize at room temperature to the most stable hydrate form of calcium hydrogenurate, the hexahydrate Ca(C5H3N4O3)2 6H2O. The solubility product constants for this hydrate were determined at different temperatures. Completely anhydrous, stable in inert atmosphere, nearly amorphous form of calcium hydrogenurate, Ca(C5H3N4O3)2 was obtained by the appropriate thermal treatment of Ca(C5H3N4O3)2L3 or Ca(C5H3N4O3)2 nH2O, n=2, 3, 6. Factors influecing formation of a particular hydrate form, structural, thermal and spectroscopic properties of all these calcium hydrogenurates are correlated. 1. N. Brničević, V. Babić-Ivančić, and H. Füredi-Milhofer, J. Inorg. Biochem., (1991) in press.

calcium hydrogenurate hydrates; complexes; transformation; solubility product

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