Gypsum accounts for sulfate sulfur and pyrite for pyritic sulfur, are occurring in coal; dissolution of their model samples were carried out using RuCl3 solution. The extent of soluble calcium from gypsum at 25 degreesC was 97.67-98.26% in 15-60 min while the extent of soluble iron from pyrite was 0.35-0.65% at 25 degreesC and 3.90-6.31% at 80 degreesC in the same time period. The rate constants for gypsum dissolution are exceedingly higher (1.12-4.23) 10(-3) s(-1), than those observed for pyrite, (1.58-3.92)10(-6) s(-1). It is observed that RuCl3 is a suitable reagent for the removal of gypsum by dissolution process. (C) 2003 Elsevier Science B.V. All rights reserved.