The effect of nitric acid leaching on the sulphur distribution in Emma and Mequinenza coal was studied here, as previous work demonstrated that nitric acid was able to remove more than just inorganic sulphur under certain experimental conditions. In contrast with standard methods, in which nitric acid is used to remove pyritic sulphur, atmospheric pressure-temperature programmed reduction (a.p.-t.p.r.) was used to specify which organic sulphur functionalities are easily removed by nitric acid treatment, and which are more difficult to remove. (C) 2000 Elsevier Science Ltd. All rights reserved.