Smoothing and interpolation of float/sink data for coals

Washability data for a coal generally consists of triplets of values of three inter-related variables:- relative density, mass and ash content. Although the M-curve incorporates details of only mass and ash content, it can be used in combination with the relationship between ash content and relative density to smooth the experimental data and to interpolate as required. The method of representation and the curve fitting procedures are described and details are given of the initial proving of the technique. Practical experience in the use of the technique is reported together with an analysis of seventy-three sets of data. Examples are given to illustrate good and poor overall fitting.