The alkali metal decamolybdate of ideal formura, A2O.10MoO3.nH2O, form a structurally related family.  The complete crystal structures of two members of which, A = K, Na, have been determined. [2, 3] For both, the framework structure consists of double chains of edge-sharing MoO6 octahedra linked by common corners which form wide (0.29nm diameter) tunnels occupied by the alkali metal ion (Fig. 1). For all these compounds the presence of wide one-dimensional tunnels suggest that there should be a rich intercalation chemistry and related properties to investigate. In this report, There are no published quantitative active energy data of decomposition available for Li and Na-decamolybdates and we present the determination of their active energies of decomposition here.