Standard partial molal heat capacities of sodium perchlorate in water from 0-90.deg. and in anhydrous methanol from -5-55.deg.

Heats of solution of NaC104 have been measured calorimetrically in water at several temperatures ranging from near zero to 90°C and in anhydrous methanol from -1055°C at concentrations ranging from about to 1.2 X m. The data have been extrapolated to infinite dilution by means of an extended Debye-Huckel equation to obtain standard heats of solution at the various temperatures. These were treated by the integral heat method to evaluate standard partial molal heat capacities for this salt in the two solvents as a function of temperature. The heat capacity curve for NaClO4 (aq) shows the characteristic maximum exhibited by other aqueous electrolytes while the heat capacity curve for the methanolic NaC104 appears to be at a maximum at the lower end of the temperature range and decreases as the temperature is increased. This suggests that the behavior of the standard partial molal heat capacities in the two solvents is similar, but that the maximum occurs in methanolic solutions at much lower temperatures.