Calcium oxalate trihydrate

Aquilano, D. and Franchini-Angela, M., 1985. Twin laws of calcium oxalate trihydrate (COT). Journal of Crystal Growth, 73, 558-562. 

Gardner, G.L. (1976) Kinetics of the dehydration of calcium oxalate trihydrate crystals in aqueous solution. Journal of Colloid and Interface Science, 54, 298-310. 

FIG. 6 Kinetic analysis of solution-mediated phase transformation of in situ precipitated calcium oxalate trihydrate (COT) into calcium oxalate monohydrate (COM), (a) Solution analysis Variation of ion activity product vs. time, (b) Solid phase analysis Total crystal volume (curve 1) and volume fractions of COT (curve 2) and COM (curve 3) vs. time. 

Donnet, M., Jongen, N., Lemaitre, J. and Bowen, P., 2000. New morphology of calcium oxalate trihydrate precipitated in a segmented flow tubular reactor. Journal of Materials Science Letters, 19, 749-750. 

Both calcium oxalate monohydrate and dihydrate - whewellite and weddelite - contain eight-coordinated Ca2+ in distorted square-antiprismatic geometry, but there is one coordinated water in the former, two in the latter. Whewellite has a layer structure through the sharing of three edges of each coordination square-antiprism with three adjacent polyhedra weddelite has a chain structure (128). The trihydrate also contains eight-coordinated Ca2+ (129). 

Calcium oxalate (723) occurs as the monohydrate (whewellite, the thermodynamically stable form under ambient conditions (724)), the dihydrate (weddellite) in plant calcium stores and in sap, or the trihydrate (725). Calcium oxalate also plays a structural role in plants. Oxalate, for example from excessive amounts of rhubarb or spinach, inhibits absorption of Ca2+ from the GIT precipitation of calcium oxalate is the reason for the toxicity of oxalates. Calcium oxalate may also occur in man, where it can appear as minute star-shaped crystals in the urine. It is the main constituent of the majority of urinary calculi in man (726,727). The relationships between dietary calcium... 

A special type of aging occurs in calcium oxalate, which at room temperature is precipitated as a mixture of dihydrate and trihydrate. Upon digestion at higher temperatures these products become metastable with respect to the monohydrate. As a result of the drastic recrystallization, coprecipitated impurities are largely removed by digestion. 

Calcium oxalate crystallizes in the form of three different hydrates. The thermodynamically stable monohydrate, CaC204 H2O (COM), crystallizes in the form of monoclinic (-101) plates [38]. Two other, metastable, crystal forms are known, the tetragonal calcium oxalate dihydrate [CaC204 (2 -1- x) HjO, x < 0.5 (COD)] and the triclinic trihydrate [CaC204 (3 - x) H2O, x < 0.5 (COT)]. COM and COD are important as the main constituents of kidney stones [39] and occur in many plants [40], and COT has been extensively investigated in the laboratory [41-44]. 

Sodium acetate trihydrate Sodium arsenate Sodium phosphate dibasic anhydrous Sodium stannate Tannic acid Titanium sulfate mordant, dyeing/printing fabrics Nickel sulfate Nickel sulfate hexahydrate mordant, dyeing fabrics Nickel sulfate Nickel sulfate hexahydrate mordant, dyeing leather Pyrogallol Titanium potassium oxalate mordant, dyeing textiles Albumen Aluminum diacetate Calcium acetate Chromium potassium sulfate Copper chloride (ic)... 

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