A Collaborative Study of the Ethylenediaminetetraacetate (EDTA) Method for Rating Agricultural Limestones. I. Reproductibility of Ratings and Correlations with Chemical and Physical Characteristics of Materials¹

Abstract

Synopsis The reactivities of 39 liming materials as rated by 12 laboratories indicate that the EDTA procedure holds considerable promise as a means of obtaining a simple numerical rating of limestone reactivity.

Use of the Intercept Method in Determining the Calcite‐Dolomite Ratio for Rating Agricultural Limestones1

“…The coefficients were similar to those of pH vs. CaCOa and pH vs. MgC0 3 (3). Theoretically, the rate of dissolution is a function of surface area in systems where the H-ion concentration and rate of di1fusion are not limiting factors (8,9), and, it has been found that the rate of solution of calcite is approximately 1000 times that of dolomite ( 8).…”

“…Sample 35 was coarser than sample 3 7, yet its surface area was larger, 1726 as compared to 1531 cm. 2 per g. (3). This larger surface area is reflected in a faster rate of solution for sample 35 and explains the apparently anomalous faster rate of solution of the dolomite in the coarser sample.…”

“…The identification, chemical composition, particle size surface area and reactivities of the samples 3…”

“…The difficulty with most analytical methods is that calcite and dolomite dissolve at different rates, that the rates of solution are dependent upon particle size and that evaluation of the combined effect is difficult by any single method. A recent collaborative study (3,10) on the rating of 40 liming materials showed that the total CaC0 3 gave good correlations with the reactivity of the materials. It has been suggested (7), however, that the calcite content might be a good measure of reactivity.…”

“…To measure the reactivity of the liming materials, Hunter et al mixed the limestones with a suspension of acid soil and measured the pH after reaction (2, 3). This suspension pH is used here as a measure of reactivity and the correlation coefficients with certain properties are shown in Table 2 for comparison with those of Hunter et al ( 3). The pH increased significantly with increasing calcite content but decreased as the proportion of dolomite increased.…”