Report issued by the Argonne National Laboratory discussing the performance of magnetohydrodynamic generators. As stated in the abstract, "an experimental study was made of the performance characteristics of a liquid metal MHD generator utilizing single-phase sodium-potassium and two-phase sodium-potassium-nitrogen fluids. The purpose of this study was to compare the generator performance with theory for single-phase flow and to determine the effects of the introduction of the gaseous phase on the generator output and efficiency" (p. 9). This report includes tables, illustrations, and photographs.