The Heat Capacity of Rochelle Salt Between -30° and +30°C

Abstract

The heat capacity of Rochelle salt has been measured in the temperature range -30° to +30°C by the method of adiabatic electric heating. Two samples of the salt have been investigated, one consisting of eleven single crystals of total weight about 123 grams, the other of small crystals, almost a powder, of total weight about 58 grams. The heat capacities of the two samples are nearly the same. They are well represented (mean deviation of individual points 0.3 percent) by the straight lines: $C_p=1.290+0.0031t \left(\mathrm{crystals}\right)$ $C_p=1.289+0.0034t \left(\mathrm{powder}\right).\mathrm{}$ The heat capacity is in joule/g.°C; $t$ is in °C. There are indications of anomalies at approximately -18° and possibly +24°C, but the maximum departure from the straight lines is less than 1 percent. The direction of the indicated anomalies and their order of magnitude is in agreement with theory. The small amplitude of the anomaly at +24° is not in agreement with the measurements of previous observers.