Four coal samples having different lump densities were sorted out and from each one of them ten ranges of particle-size and the corresponding bulk densities of each of them were determined. Empirical relations involving the bulk densities and the particle-size in microns have been developed for all the four samples. Fraction-wise variation of lump densities with bulk densities is also shown. The study not only affords to determine the load withdrawn from or produced per unit area and the volume required for a given mass of pulverized coal for its transportation and storage but also to provide a detailed picture of the fluctuation of lump densities with bulk densities of various particle-size-ranges usually encountered in problems of dust-air ignition
