DISSOLUTION KINETICS OF CACO3 IN COMMON LABORATORY SOLVENTS

The dissolution of calcium carbonate with both organic and aqueous sol vents was examined quantitatively and kinetically. Neither ethanol and nor acetone at 25-degrees-C dissolved appreciable aragonite or calcit e, even after nearly ten days. Bleach (sodium hypochlorite) was a much less effective solvent than deionized water, producing little or no n et calcium in solutions in contact with calcium carbonate. Although ex posure to sodium hydroxide solutions also yielded relatively small con centrations of calcium in the fluid, characterization of the exposed c arbonate grains by X-ray powder diffraction and by light microscopy re vealed extensive replacement of the CaCO3 by Ca(OH)2, calcium hydroxid e (portlandite). A solution of Alconox(TM), a commercial laboratory an ionic detergent, was about half again as potent as deionized water, an d hydrogen peroxide proved to be many times more corrosive of calcium carbonate than deionized water. These results are consistent with publ ished and anecdotal observations of the effects of laboratory preparat ion protocols on calcium carbonate. Our quantitative data permit the r esearcher to assess the potential for a treatment procedure using any of these solutions to compromise the integrity of a sample of calcium carbonate.