[Preparation and analysis by x-ray diffraction of three crystalline forms of calcium oxalate in a mixture]

The present work describes a method for analysing, quantitatively, mixtures of the three calcium oxalate hydrates which are the most important components of human kidney stone. The method consists in measuring and comparing the relative intensities of X-ray diffraction peaks obtained by means of the so-called powder method. We first give the composition of the solutions from which the three hydrates were grown separately. Second, we briefly describe the principle of the X-ray quantitative phase analysis and give the results we obtained by analysing binary and ternary mixtures of the three solid phases of calcium oxalate. We show that the proportion of either phase can be estimated with an accuracy of about 2 or 3 wt%.