The preparation of calcium oxalate dihydrate crystals

Abstract

Two simple related methods for exclusively preparing well-developed tetragonal bipyramidal crystals of calcium oxalate dihydrate at moderate supersaturations and at ambient temperature are reported. These crystals have an average length of 5.7-7.2 pm and are easy to wash and filter. One of the methods is suitable for studies of the kinetics of spontaneous precipitation and crystal morphology of the oxalate in the presence and absence of additives. A tentative mechanism is given to account for the sole formation of this particluar hydrate.At 70 "C a mixture of the monohydrate and dihydrate phase were formed with various crystal shapes and sizes. These phases were also identified in the presence of sucrose at this temperature, although some of the crystals contained tetragonal habit as obtained at ambient temperature.

Solubility of the Three Calcium Oxalate Hydrates in Sodium Chloride Solutionsand Urine-Like Liquors

“…Therefore, the method to prepare COD given in Ref. [13] is recommended being simpler than that of Ref. [12].…”

The effects of silica and sugar on the crystallographic and morphological properties of calcium oxalate

“…COD crystals were also found to exhibit stellate shape (Figs. 8B and F), a habit previously observed under high temperature and sucrose concentration [18]. The crystal habits of COT, on the other hand, displayed triclinic platelets at low SiO 2 SS and a mixture of flattened platelets and needles at high SiO 2 SS (Figs.…”

Sequestration of Sr(II) by calcium oxalate—A batch uptake study and EXAFS analysis of model compounds and reaction products

“…The incident Xray beam was detuned 50% at 16,320 eV to minimize beam harmonics, and beam size at the sample was reduced to 2 Â 20 mm using vertical and horizontal slits. SrOx anhydrate powder, synthesized using the method of Doherty et al (1994) for CaOx synthesis, was heated at 200°C for 24 h to ensure formation of the anhydrous phase, which was confirmed by XRD to be greater than 99% pure. Sr K-edge EXAFS spectra of a third model compound, SrSnO 3 , were collected in transmission mode at the LURE synchrotron radiation facility (Orsay, France) using a Si(331) double crystal monochromator.…”

“…The method of Doherty et al (1994) was used to prepare calcium oxalate monohydrate (CaOx), and phase purity was determined to be greater than 99% by powder X-ray diffraction (XRD) using a Rigaku powder X-ray diffractometer. The N 2 -BET surface area of the synthesized CaOx particles was measured using a Micromeritics ASAP 2020 Automatic Physisorption Analyzer and was found to be 6.2 ± 0.1 m 2 g À1 .…”