A thin film infrared cell technique has been developed employing an aqueous system for the rapid analysis of the sulfate content of calcined limestones which have been reacted with SO₂ in a flue gas. Accurate analyses can be reproducibly conducted by dissolving the reacted limestone material in tetrasodium EDTA (ethylenediaminetetraacetic acid) saturated aqueous solutions and obtaining spectra of those in a 0.003 mm infrared liquid cell. For the infrared deterrminations an identical cell, containing a saturated EDTA aqueous solution, is placed in the reference beam of the spectrometer. Results obtained are in good agreement with determinations made independently by different techniques. It has been demonstrated that similar analysis can also be conducted for the carbonate and hydroxide contents of limestone with the use of EDTA saturated D₂O as the solvent. The general approach should be useful for many solids analyses. -- AATA