THERMAL PROPERTIES OF CARBONIC ACID AT LOW TEMPERATURES. 361 



interchanger enabled the temperature of the liquid to be carried down to 50'6 C., 

 eleven degrees lower than before. The interchauger is made of two concentric copper 

 pipes, 10 feet long, coiled into a ring 9-inch diameter. It is the same piece of 

 apparatus which is described in the former paper on p. 92. By means of this 



e 



K) --05 



ENTROPY 



interchanger the liquid CO 2 was cooled before passing the throttle valve by the cold 

 gas leaving calorimeter II. , an arrangement which considerably increases the available 

 refrigeration ; it was only used for the last experiment at the lowest temperature. 

 The arrangement of the apparatus (including the interchanger) is shown in fig. 5. 



VOL. CCXV. A. 



3 c 



