Phase Transitions of Calcium Oxalate Trihydrate and Epitaxy in the Weddellite-Whewellite System

Authors

Sergio Deganello, University of Chicago

Abstract

The phase changes calcium oxalate trihydrate-weddellite, weddellite-calcium oxalate monohydrate and calcium oxalate trihydrate-whewellite are individually examined at the atomic level from a theoretical point of view; concomitantly the topological requirements necessary for phase stability are clarified for each structure type. In solution a sequential series of phase transitions according to the steps calcium oxalate trihydrate-weddellite-whewellite is not likely to be energetically favoured; direct conversion of calcium oxalate trihydrate to whewellite should be, instead, ordinarily expected.

It is formally demonstrated that along two axial directions a set of atoms is in essentially identical positions in both weddellite and whewellite. This notwithstanding, it is concluded that epitactic catalysis cannot and should not be considered a common mechanism for the formation of whewellite from weddellite (and vice versa) or of kidney stones in general.

Recommended Citation

Deganello, Sergio (1986) "Phase Transitions of Calcium Oxalate Trihydrate and Epitaxy in the Weddellite-Whewellite System," Scanning Electron Microscopy: Vol. 1986: No. 4, Article 45.
Available at: https://digitalcommons.usu.edu/electron/vol1986/iss4/45