A simple model is formulated to determine the effect of temperature on the filtering ability of HGMS devices. An optimum temperature range is observed to exist for which the capture of ash-forming minerals and inorganic sulfur in liquid coal is at a maximum. Model will serve as a framework for analyzing experimental data in future. In the past, some pertinent, independent variables such as particle size, slurry velocity and applied magnetic field which affect the performance of HGMS de-Vices, have somewhat been investigated both theoretically and experimentally. The effects of these important variables have been well established. A program is currently underway at the M.I.T. Francis Bitter National Magnet Laboratory to study the applicability of HGMS to products from coal liquefaction processes. As part of this program, the effect of temperature on the performance of filtering ash-forming mineral impurities and inorganic sulfur from liquefied coal is being explored. This introduces an additional variable- temperature -which is to be investigated among other relevant variables of the system. In particular, by varying the operating temperature the trade-off, between the lowering of the viscosity of the fluid as the temperature is increased and the attendant decrease in the magnetization of magnetic particles, is to be studied. In view of these considerations, a simple model has been formulated to predict the effect of temperature on the filtering ability of HGMS devices.