The present Bureau of Mines investigation measured low-temperature heat capacities of nibr2 (8 to 302 k) and niso4 (9 to 70 k) by adiabatic calorimetry. The standard entropies (s deg, 298.15 K) of nibr2 and niso4 were calculated as 29.26 +/- 0.06 Cal/deg mole and 24.21 +/- 0.04 Cal/deg mole, respectively. (1 Cal = 4.1840 Joules.) Heat-of-solution measurements of anhydrous nibr2 were used to determine its enthalpy of formation (ahf deg, 298.15 K) as -50.64 +/- 0.31 Kcal/mole. High-temperature enthalpies of nibr2 and niso4 were measured by drop calorimetry to 1,150 k and 1,002 k, respectively. Enthalpies, heat capacities, and related formation functions are tabulated to 1,200 k.