The principal objective of the research was to validate the following wet chemical methods for sulfur oxides: the barium chloranilate procedure, the barium ion-thorin procedure, and lastly, a simplified method, which is not specific for sulfate, which was also used to analyze aliquots of the SO2 samples. The first phase of the program evaluated the collection and analysis methods. During second phase, the revised chemical methods were tested at uncontrolled coal, uncontrolled oil, and controlled coal-fired power plants. A modification to the program enabled the data collected in the field to be utilized in preparing the national emission standards for sulfur oxides. The results obtained in fossil fuel-fired power plants and in the Walden pilot plant are given in Section 1. Section 2 discusses the results for the other (noncombustion) stationary sources. For each source tested, a brief description of the process is provided. The appendix contains a detailed write-up of the analytical methods used, the Pb titration method developed under this contract and data obtained on solid sorbents for collection of sulfur oxides.