Wetting of powdered coals by alkanol-water solutions and other liquids

The wetting rates of powdered coals by alkanol-water solutions have been measured. A critical concentration of each alkanol is needed before any wetting occurs and this critical wetting concentration is lower for alcohols with longer carbon chains. A critical surface tension of 0.033 J m^?2 for Pocahontas No. 3 coal is estimated from the measured wetting concentrations. Studies with a Calvet microcalorimeter show that the heats of immersion of powdered coal in water-methanol mixtures vary smoothly with changing concentration, reaching a maximum value of 16 J g^?1 at 30 mol % methanol. Both for alkanols and other liquids, the heat of immersion of coal dust is released over long periods of up to nine hours.