The electrochemical reaction of lithium with SnO and with SnO:0.25 B2O3:0.25 P2O5 glass was studied in-situ using Sn-119 Mossbauer effect spectroscopy in electrochemical cells equipped with beryllium windows. The experiments confirm our previous work that showed that the first two lithium atoms per formula unit react with the oxygen bonded to tin, forming-clusters of tin metal and Li2O, As further lithium is added, the tin clusters alloy with lithium. The alloy reactions are easily observed in Mossbauer spectroscopy, even in SnO:0.25 B2O3:0.25 P2O5 glass, where X-ray diffraction did not discern the Li-Sn alloy phases well. Most interesting, however, is the dramatic variation of the total Mossbauer absorption intensity as a function of the amount of lithium that has reacted with the electrode. Since the number of tin atoms in the sample is constant as the lithium content changes, such intensity variations can only be caused by changes in the fraction of Sn atoms undergoing recoil-free absorption. The recoil-free fraction depends on the mean square displacement of the tin atoms from their equilibrium positions. This, in turn, depends on the size of the grains of the Li-Sn alloys and upon the nature of the bonding in the alloy phases, as reflected in their Debye temperatures or in their melting points.