Co-Authors:
Stern, R., Soil and Irrigation Research Institute, Private Bag X79, Pretoria, 0001, South Africa
Alperovitch, N., Inst. of Soils and Water, ARO, P.O. Box 6, Bet Dagan, 50250, Israel
Levy, G.J., Soil and Irrigation Research Institute, Private Bag X79, Pretoria, 0001, South Africa
Abstract:
The presence of gypsum in soils has complicated the determination of particle-size distribution (PSD) due to the difficulty in dispersion of the soils. A technique for rapidly removing gypsum from highly gypsereous soil samples is presented here, using the resin method. A mixture of Na and Cl resins enhances the complete dissolution of appreciable amounts of gypsum in salt solutions within 6 h. The dissolved calcium and sulfate exchange with the sodium and chloride on the resins, resulting in a solution containing primarily Na and Cl ions. The increase in electrical conductivity of the gypsereous soil solution is indicative of the amount of gypsum initially present. Thus, from a calibration curve, the amount of gypsum present in a soil sample is accurately determined. After the excess soluble salt has been removed, a stable clay and silt suspension is obtained, enabling a PSD determination using the pipette method. Removing gypsum from soil samples using the resin method has no significant effect on the particle-size distribution of the soils studied. © 1989 Williams & Wilkins.