THEEMAL PROPERTIES OF CARBONIC ACID AT LOW TEMPERATURES. 371 



curve, would be shifted almost exactly the same distance to the right, pivoting round 

 the point B' which has the same I as B on the pressure curve. 



I 



ENTROPY 



The constant I lines would hardly be shifted. They are set out from points on the 

 limit curve in the way explained on p. 80 of the former paper, and calculation shows 

 that they would only be shifted about one-tenth as far as the limit curve is shifted. 

 Thus on the 50 C. line they would only be moved about O'OOOo carnots to the ri^ht. 



APPENDIX IV. 



A Method of Plotting tlie Results of Throttling Experiments. 



In the following method the results of the throttling experiments are used to draw 

 all the constant-pressure curves but one ; the position of that one is assumed to be 

 known. The pressure curves drawn in this way should coincide, if the chart is 

 correct, with the curves drawn by means of the observed specific heat of the gas. 



Let CHAA' A" be the pressure curve _p,, assumed to be correctly drawn, on which 

 A, A' ... represent the starting points of a number of experiments throttling down to 

 a second pressure p a . Let A be the starting point of the experiment beginning at the 

 lowest temperature, and let the observed final temperature, when throttling down to 

 p. 2 , be K . Draw a horizontal line at this temperature. It is required to find the 

 point B on this line representing the final condition. 



3 D 2 



