A MICRO-PIPETTE METHOD FOR WATER DISPERSIBLE CLAY

The clay percentage determined by mechanical means in distilled water without the removal of organic matter and soluble salts and use of a c hemical dispersant, is referred to as water dispersible clay (WDC). In this study, a ''micro-pipette'' WDC method is developed and described . The method increases laboratory production, i.e., number of samples per day, and yet requires less laboratory space and time. In addition, this method yields, for most soils, WDC values comparable to those va lues obtained by the standard SCS ''macro-pipette'' method. Statistica l analysis of variance (ANOVA) for determination of WDC percent indica tes nonsignificant effects at alpha = 0.05 for both method and method times soil but significant effects for method times soil interaction t erm at alpha = 0.10. In order to characterize the particle-size distri butions, a moment analysis was run on each of the 14 soils. In this st udy, the distributions of most soils measured by the ''macro-pipette'' method are not significantly different by the ''micro-pipette'' metho d. This abbreviated method may represent a significant savings for bot h high-volume characterization laboratories and research and developme ntal work. This application of the measurement of WDC may also be modi fied for use in the soil survey field office.