Coals as Colloid Systems

Abstract

IN a memoir on the geology and coal resources of Korea State, Central Provinces, published in 1914 (Memoirs, Geological Survey of India, 41, p. 180), I suggested that the bright coal of the Barakar series “judging from its brilliant conchoidal fracture is of the nature of a colloidal substance.” I find that H. Potonié had noted the colloidal nature of humus in 1911, whilst Drs. Stopes and Wheeler, in their paper on the “Constitution of Coal,” mention H. Winter as believing in the colloidal nature of coal in 1913, the reference quoted (Glülckauf) not being, however, accessible to me. Later authors have referred to the same point, but I have not noticed accounts of any research specifically directed towards the study of coals as colloid systems. It may be useful, therefore, to refer briefly to data derived from a study of certain Indian coals that appear to provide definite evidence on this question.