Phase transitions of calcium oxalate trihydrate and epitaxy in the weddellite-whewellite system.

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.

• Authors: S Deganello
• Journal: Scanning electron microscopy (Scan Electron Microsc) Issue Pt 4 Pg. 1721-8 ( 1986) ISSN: 0586-5581 [Print] United States
• PMID: 3810035 (Publication Type: Comparative Study, Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Calcium Oxalate

Topics

• Calcium Oxalate
• Crystallography
• Models, Molecular
• Molecular Conformation