XII. Thermal properties of carbonic acid low temperatures

Abstract

In a former paper (1) the authors described a series of measurements on the thermal properties of Co 2 and the construction of a θ ø chart embodying those results. It was pointed out that the superheated area of the chart was incomplete, the constant pressure lines being only approximately accurate and the total heat (I) lines omitted. It was also pointed out that throttling experiments on the superheated gas would form a valuable check on the accuracy of the chart, and the construction of an Iø chart was postponed till more accurate measurements should have been made on the superheated gas and the whole had been checked by throttling experiments. The present paper describes the additional experiments required to complete and check the θ ø chart, including a re-measurement of the total heat of the liquid for which some extrapolated values had been used before, and finally the construction of the Iø chart. This chart has been constructed graphically, as the θø chart was, directly from the observed data and its accuracy checked in various ways by thermodynamic equations. These equations apply quite generally to all Iø charts and are independent of tire particular properties of carbonic acid.