Abstract
The particle size distribution of a fine portion of soils is usually determined using sedimentation principles and hydrometer method. Some hydrometer test methods, such as South African Standard (SANS3001, 2014) and Guidelines laid by International Soil Reference and Information centre (ISRIC, 2002) make provision for the effect of the dispersing agent in the solution on readings recorded during the test. Test methods that do not make such provision may be incorrectly yielding inflated fines (including clay) contents. This paper discusses the results of an investigation into the effect of dispersants when applying TMH1 (1986) test method. The results have been compared using phosphate dispersants such as Calgon, sodium pyrophos-phate decahydrate and sodium tetra pyrophosphate in various concentrations. The use of dispersants in higher concentrations produced anomalous increases in the hydrometer readings and the results indicated the im-portance of understanding the effect of dispersants on fine soil particle size distribution analyses.