Technical report discussing that the deuterium concentration of heavy water can be determined by equilibrating the water with deuterium gas in the presence of a catalyst with subsequent analysis of the equilibrated gas on the mas spectrometer. The apparatus for equilibration analyses maybe be considered in three parts: 1) apparatus for introducing the ingredients into the reaction chambers; 2) the reaction chambers; 3) the mass spectrometer for analysis of the equilibrated gas. The isotopic composition of the deuterium gas to be used as the starting material is primarily governed by what gases are available. In general it is best to use gas within about one percent on either side of the final equilibrium composition. No reaction takes place between deuterium gas and water molecules in the absence of a catalyst. Platinum oxide is used as the catalyst.