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Speciation 98: Abstracts
Zhonghua Wang1, Jürgen Seidel2, Gert Wolf 2 and Erich Königsberger1
1 Department of Physical Chemistry, University of Leoben, A - 8700 Leoben, Austria ;
2 Department of Physical Chemistry, Technical University Bergakademie
Freiberg, D - 09596 Freiberg, Germany
Anhydrous uric acid and its dihydrate are frequently found as constituents of renal calculi, whereas xanthine is only detected in less than 1% of all kidney stones. Given that exact solubilities data of these substances are required to estimate the risk of stone generation, it is most remarkable that these quantities were not very precisely known, particularly for conditions most pertinent to urolithiasis.
Therefore, a comprehensive solubility study in the uric acid sodium urate water system was performed at 25, 32, 37 and 42 oC [1]. The measurements were carried out in various salt solutions and artificial urine of ionic strength 0.15 0.30 mol dm3. Since the temperature dependence of the reported solubility data scatters considerably, the enthalpy of dissolution at pH = 7.5 of the two uric acid phases was determined calorimetrically for the first time.
Only one solubility study on xanthine as a function of pH and temperature was reported in literature [2]. Thus a systematic re-determination of xanthine solubilities was carried out and the results were correlated with calorimetrically measured enthalpies of dissolution.
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