Effect of carbonate minerals on volatile matter of coals

Coals high in carbonate minerals show abnormally high VM on dmmf basis. This abnormality has been shown to be due to the presence of iron carbonate. Effects of the presence of different carbonate minerals on VM have been estimated, and a formula is advanced for estimating VM on dmmf basis of a coal having a particular distribution of carbonate minerals: $\text{VM}\text{on dmmf basis}\text{=}\text{As analysed}\text{VM ? 0.1 Ash ? 1.3 CO}{}_2\text{100 ? (MM + Moisture)}\text{× 100}$