Sets out a method whereby the carbonate carbon of higher rank coal is determined gravimetrically. Hydrochloric acid is added to the coal in a reaction tube and the carbon dioxide gas given off is dried and absorbed on soda asbestos. The change in mass of the absorption tube is then determined. The carbonate carbon content of the mineral carbonates of a coal is required to correct the determined percentage of total carbon and volatile matter when calculating organic carbon and organic volatile matter respectively.