A new rapid approach for evaluating limestone quality by an automanometric isothermal apparatus
1991
SAJWAN, K. S. | Evangelou, V. P. | LUMBANRAJA, J.
Presently, agricultural limestone quality is determined by employing dry sieving and acid dissolution followed by analyses with atomic absorption. These procedures are lengthy and costly. A rapid technique has been developed employing automanometric-isothermal analysis based on acid dissolution of limestone samples in 1.5 mol·L HCl. This technique has shown that there is a linear relationship between the natural logarithm of the first-order acid dissolution constant and the mean particle diameter or surface area for calcite and dolomite. This linear relationship extends from mean particle diameter of 0.2 mm to 1.5 mm or from a surface area of 0.03 m·g to 0.01 m·g. For particles with mean diameter less than 0.2 mm, or surface area greater than 0.03 m·g, the rate of dissolution and its dissolution constant remains relatively unchanged. The rate of dissolution of limestone particles with a surface area greater than 0.03 m·g appears to be an intrinsic property of the crystal for calcite and dolomite. However, there is a 2.3-fold minimum difference and an 18.2-fold maximum difference in the dissolution constant between calcite and dolomite. The evaluation of a number of unknown limestone samples from quarries of western Kentucky and West Virginia shows that these samples have surface areas greater than 0.17 m·g (mean diameter less than 0.2 mm), and thus their agricultural limestone value depend primarily on their crystallinity and chemical composition. The study demonstrates that automanometric analysis can be used as a rapid means to evaluate lime quality or can offer additional lime quality information to that obtained by chemical analysis and dry sieving.
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