Using solution calorimetry, the following heats of reaction were determined: (1) nacn(c) + 1/2cu2o(c) + 129h2o(1), -> cucn(c) + naoh.128.5H2o, ah = -13.44+/-0.10 Kcal/mole. (2) Hcn(1) + naoh.128.5H2o, -> nacn(c) + 129.5H2o(1), ah = -2.52+/-0.02 Kcal/mole. From these reactions, the heats of formation for cucn(c) and hcn(1) were calculated to be 22.7+/-0.4 Kcal/mole and 24.9+/-0.4 Kcal/mole, respectively. Reaction 2 was made to check the consistency of literature values for heats of formation of hcn and nacn. Adiabatic calorimetric measurements between 10 deg and 400 deg k showed the entropy and heat capacity of cucn(c) to be 21.51+/- 0.06 Eu and 14.58+/-0.04 Cal/mole deg, respectively, at 298 deg k. A broad anomaly in the heat capacity was found in the temperature range 285 deg to 320 deg k. The heat of transition associated with this anomaly was less than 1 cal/mole, the sensitivity of the measurements. Work done in cooperation with the University of Alabama.