Since 1901, when G. G. Stokes published his equation for drag force on a uniform sphere settling in a liquid, researchers have searched for a modification of this equation that would predict particle settling behavior in concentrated suspensions such as sludges. During the 1960’s, researchers such as Michaels and Bolger (1962) and Javaheri and Dick (1969) developed an index of the relative amount of water associated with a floc particle that appeared to have broad application in predicting sludge settling behavior. The objective was to attempt to apply various direct laboratory methods of wet particle density to the analysis of sludge floes. The second objective was to use the analysis of Javaheri and Dick (1969) to evaluate the thickening characteristics of four non-biological sludges including the relevance of particle size, density, and water content to thickening rates. Aggregates of sludge floes do not appear to retain their integrity during mechanical dewatering, although they do over the linear portion of the batch thickening curve. It appears that the floc density rather than the aggregate density may represent the highest bulk density achievable by mechanical dewatering. The aggregate volume index (AVI) of Javaheri and Dick (1969), which can be used to determine aggregate size and density, predictively described the settling behavior of the four chemical sludges evaluated. This indicates that the analysis of Javaheri and Dick (1969) may be the first mathematical description of settling of slurries broadly applicable to the settling of water and wastewater treatment sludges.