The application of interface settling rates in hindered settling to the determination of the mean particle radii

The settling behaviour of concentrated suspensions of glass ballotini in water and in glycerine-water mixtures is determined. A nominal diameter could be assigned to the various grades of glass ballotini, so the calculation of the diameter from the settling mass of suspended material and the clear supernatant could be checked. The nominal diameters were based on optical microscopy experiments. The value of the diameter can be calculated either by extrapolation of data to infinite dilution conditions or by the use of various formulae which can be represented as modifications of Stokes' Law. It is shown that reasonable results can be obtained in a number of cases. The behaviour of some of the algebraic functions in these calculations is a subject of a detailed analysis. In one set of experiments the data are collected on a monosized dispersion of ballotini but the work is extended to cover suspensions of different sizes.