We ask for 3 days on GEM to study in-situ the decomposition of the Na-substituted LiNH2 phases, Li1-xNaxND2, LiNa2(ND2)3, Li3Na(ND2)4 and their reactions with LiD. LiNH2 is the fully absorbed end member of the Li3N-Li2NH-LiNH2 system. We have performed high resolution X-ray diffraction measurements on the LiNH2:NaNH2 system and shown that there are three main reaction products Li1-xNaxNH2, LiNa2(NH2)3 and Li3Na(NH2)4. The 'Na-doped' amides are less stable than LiNH2 and decompose at lower temperatures. It has also been observed that there is significant non-stoichiometric behaviour within the formation of these compounds. The high resolution of GEM coupled with the ISIS in-situ gravimetric analysis will allow us to monitor the different temperatures of destabilisation of the phases while monitoring the respective crystal structures with particular reference to hydrogen behaviour.