Melamine-promoted crystal growth of calcium oxalate monohydrate from calcium nitrate and oxalic acid

The influence of melamine with different concentrations on the spontaneous batch crystallization of calcium oxalate monohydrate was investigated. The self-assembly of different sizes of calcium oxalate monohydrate crystals was achieved by layering a mixture of ethanol–water solutions of calcium nitrate and oxalic acid with different concentrations of melamine at room temperature. The presence of melamine accelerated the growth of large-sized calcium oxalate crystals but inhibited the total weight of the crystals. Precise EDX, IR and powder X-ray diffraction analyses of the product permitted its chemical composition to be determined. Such analyses lead to the finding that the reactions produced calcium oxalate monohydrate, that their average size increases from 1.5 × 10− 3 to 4.4 × 10− 3 cm3, while the total weight decreases from 3.6 to 1.5 mg with an increase of the amount of melamine. This finding is particularly significant for the renal and kidney failure due to the growth of large calcium oxalate monohydrate crystals in the presence of melamine.