A methodology for identifying inorganic compounds in particulate emissions from fossil fuel combustion processes is described. Samples collected from power plants burning coal and oil fuels of different compositions provided a typical range of fly ashes for the investigations. Elemental (cation/anion) determinations of these samples were used to guide the compound methodology work. Fourier transform infrared (FT-IR) was the main technique used for compound identification. Water extractions of the samples proved to be effective for separating soluble sulfate compounds from insoluble oxides and silicates, and this reduced the complexity of the compound forms remaining in the water soluble and water insoluble phases. A library of FT-IR reference spectra, prepared and stored for ready recall, was found essential for identification of compound species.