On an inversion point for liquid carbon dioxide in regard to the Joule-Thomson effect

• Published in: Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1914
• Subjects: Carbonic acid
• Online Access: http://dx.doi.org/10.1098/rspa.1914.0002; https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.1914.0002

In a paper published recently in the ‘Philosophical Transactions’ “On the Thermal Properties of Carbonic Acid at Low Temperatures,” Prof. C. Frewen Jenkin and Mr. D. R. Pye give, amongst other results, those obtained from a series of measurements of the Joule-Thomson effect for liquid CO 2 at various temperatures. These results are tabulated in Table V of their paper. They are of particular interest because, within the range of temperatures to which they correspond, they find an inversion point for the Joule-Thomson effect, i. e ., a temperature at which the effect changes over from being a cooling (at higher temperatures) to being a heating. As they themselves say: “No experiments on the Joule-Thomson effect for liquid CO 2 appear to have been published” previously; and as they admit that it is not easy to say what effect the presence of a trace of air (which was there) may have on their results, any method of testing them should prove of value. Such a test can be made by utilising the values of the specific volumes of liquid CO 2 which they give in a diagram on p. 78 of their paper. Method of Test . If the drop of pressure employed may be treated as a differential the Joule-Thompson effect is given by the equation C p (∂T/∂ p ) E+ px = T(∂ v /∂T) p - v = T 2 ∂/∂T.( v /T) p . The inversion point must therefore correspond to a minimum (or maximum) value of v /T.