Determination of sulfate sulfur in coal has been done by using organic acids, namely: acetic acid, oxalic acid and tartaric acid. The results have been compared with those of the ASTM HCl method. It is found that 0.5 M tartaric acid is a suitable reagent by which sulfate sulfur can be effectively extracted. Minor increases of sulfate sulfur in the tartaric acid extraction over that of HCl extraction may be correlated with the solubility of sulfate minerals which seem to be unleached with the mineral acid. This has been verified by studying the solubilities of gypsum and pyrite in the tartaric acid solution. Increased solubilities of gypsum and of sulfate obtained from pyrite have been found as the concentration of tartaric acid is increased. The variation of sulfate sulfur content in the extractions of 0.5 M tartaric acid and 4.8 M HCl is not significant. As the mineral acid could degrade the organic sulfur (which can affect its determination, calculated by difference), the use of tartaric acid is strongly recommended for the determination of sulfate sulfur in coal.