IF coal be regarded as a conglomerate of two main types of compounds, the one readily yielding inflammable gases and vapours on heating to a comparatively low temperature, the other requiring a higher temperature of m0r0 prolonged duration to decompose it freely, it can be understood that variations in the proportions in which these different types exist in different coals should cause corresponding variations in the chemical and physical properties of the coals. A property, common to all

more »

... which would appear to depend essentially on the proportion of readily-decomposed constituents present, is their " inflammability " when in the form of dust. The author has made a number of determinations of the relative inflammabilities of dust8 from different coals of known composition, which form the basis of t,he Second Report of the Explosions in Mines Committee of the .Home Office. I n the present paper the results recorded in that Second Report are discussed from a different point of view. A t the concIusion of Part 11. of this research (T., 1911, 99, 649) it was showr, that one coal may contain a higher percentage of " volatile matter " than another, and yet not yield so great a volume of paraffin hydrocarbons on distillation at a low temperature; and, further, that for dusts of the same degree of fineness the ease with which their inflammation was effected appeared t o depend on the percentage of paraffin-yielding constituents present, and not on the percentage of volatile matter. That there should be no relationship between the inflammabilities of different coal dusts and their contents of volatile matter, as