Note on the specific heat of water

Abstract

In a paper on the “Specific Heat of Water and the Mechanical Equivalent of the Calorie” were given the figures from 0° to 80°C. which resulted from our investigation. These figures agreed very fairly with those of some other observers, but differed considerably from the corrected figures of Callendar and Barnes. In our curve there was a minimum value of the specific heat at about 25°C., and a rapid rise afterwards from 25° to 60° of nearly the same magnitude as the fall from 0° to 25°. In the curve of Callendar and Barnes the minimum was not reached till 38°C., and thereafter the rise was much slower. Callendar soon after devised a novel method of “continuous mixture” by means of an ingeniously devised heat exchanger, and applied this apparatus to test his former results in this range between 60° and 100°. Water at about 100°C. from a heater was passed through the heat exchanger against water from a cooler at from 25° to 35°C. The result of these experiments indicated that the ratio of the mean specific heat from 69° to 100°C. to the mean specific heat from 25° to 56°C. agreed within 1 in 5000 with the ratio derived from Callendar’s formula based on the figures of Callendar and and Barnes. These results of this new method were published in Callendar’s Bakerian Lecture in 1912, and were made the basis of a criticism of our results and those of other observers.