Diphenyldiethynylsilane (DPS), diphenyldiethynylgermane (DPG), diphenylgermane (DG), e,~-dihydridopolyvinylenediphenylgermyl (PVG), and the copolymer (PVSG) consisting of regu- larly alternating vinylenedlphenylgermyl and vinylenediphenylsilyl units were prepared by the methods of (i, 3). The total impurity content (mole %) of these monomers, foundcalorimetri- cally from the melting point depression, was 1.00 0.01 in DPS, 0.236 0.003 in DPG, and 1.00 0.01 in DG. The elemental analyses of the monomers and polymers supported their for- mulas to within 0.5%. The number average molecular weights Mn, determined by ebulliometry, were 1400 for PVG and i0000 for PVSG. Heat Capacity and Thermodynamic Functions. We used an adiabatic vacuum calorimeter (4) for the measurements of the heat capacity (Cp ~ of DG; this provided an accuracy of 0.2% in Cp ~ in the solid and liquid states. We took the functions H~176 S~ and G~ - H~ in the 0-330~ range from published work for DPS (5), for DPG from (6), and for PVG and PVSG from (7). The calorimeter was charged with 5.3498,10 -3 kg of DG. In 22 series of measurements we got 113 experimental points of Cp~ their scatter about the averaging curve Cp ~ = f(T) did not exceed 0.2%. In this temperature range DG is in the crystalline and liquid states. Its melt- ing point Tm ~ = 239.78 0.01~ and its depression in the sample was AT = 0.341~ Three