A method is presented for transforming hysteretic magnetization curves into their corresponding reversible magnetization curves. This procedure permits the determination of the thermodynamic critical fieldHc; the lower critical fieldHc1; the upper critical fieldHc2; and the Ginzburg‐Landau parameters &kgr;1and &kgr;2, which are found to be equal for each corrected magnetization curve for samples containing up to 28 at.&percent; In. Large, composition‐dependent, hysteresis effects are noted in the magnetization curves of these Pb&sngbnd;In samples.