Mössbauer spectroscopy measurements were made to observe alloy formation and interaction of tin with the alumina support in two (\mathrm{Pt}-\mathrm{Sn} /) alumina catalysts. The catalysts were rich in tin with an atomic ratio of (\mathrm{Pt}: \mathrm{Sn}=0.7: 1). One was prepared by coimpregnation and the other by a sequential impregnation technique. Spectra of samples reduced in a stream of (10 % \mathrm{H}{2}) in argon gave evidence of a solid solution of tin in platinum with a composition approaching (\mathrm{Pt}{3} \mathrm{Sn}) for most reduction conditions. A large fraction of the tin, (70-80 %), interacted strongly with the alumina and did not alloy with the platinum. Two stannous species were identified in the nonalloyed fraction. One was produced by strong interaction with the alumina and the other was a surface ion. Steaming produced large stable crystallites including the intermetallic, (\mathrm{Pt}{3} \mathrm{Sn}), and (\mathrm{SnO}{2}). The spectroscopic data were supported by TPR measurements. The results show that platinum and some of the tin reduce between 400 and (700^{\circ} \mathrm{K}) with formation of the alloy. The remaining tin reduces to the stannous state between 800 and (850^{\circ} \mathrm{K}). 1993 Academic Press. Inc.