74 PROCEEDINGS OF THE AMERICAN ACADEMY. 



tions of the change of volume at 20° gave for successive intervals of 

 500 atmos. 0.0509, 0.0278, 0.0233, and 0.0195 respectively, against 

 0.0404, 0.0289, 0.0227, and 0.0184 of Amagat. The agreement is 

 fair, except of course for the first interval. The recent work of 

 Richards gives 0.0370 for the change of volume at 20° and 500 kgm. 

 against 0.0429 given in the tables. It is evident that the work of 

 Richards and of Amagat is here in very essential disagreement. 



The volume of ethyl iodide as a function of pressure and tempera- 

 ture is given in Table XV and in Figure 19. 



When these computations were made there were no values of the 

 initial compressibility with which to compare the results. Accord- 

 ingly the value necessary to give the change of volume in the tables 

 was used in every case. The recent data of Richards give O.O49I for 

 the initial compressibility at 20°. This is considerably lower than 

 the value shown in the curves, O.OJOS. This simply means again 

 that Richards finds a much smaller compressibility than Amagat. 



Cp for ethyl iodide has apparently been determined only by 

 Regnault^^. He gives 13.19 at - 30°, 13.60 at 0°, 14.03 at 30°, and 

 14.44 at 60°. The increase with temperature is linear. 



V. Discussion of Thermodynamic Properties. 



In the following sections the general characteristics of the several 

 thermodynamic functions will be discussed. The discussion will 

 include suggestions as to what modifications it may possibly be neces- 

 sary to make in our conceptions of a liquid, or what features that we 

 have neglected at low pressures it may be necessary to emphasize 

 at high pressures. Incidentally in the course of the discussion, 

 suggestions will be made bearing on the theory of liquids, but any 

 detailed examination of the problems that confront us in trying to 

 frame a theory of liquids valid for high pressures will be reserved 

 for section VI. 



Volume. — The tables and diagrams of volume as a function of 

 pressure and temperature have already been given, but with little 

 comment. 



One of the significant facts about the change of volume is in regard 

 to the volume at infinite pressures, that is, the so-called volume of 

 the molecules themselves, which is one of the quantities entering 

 into nearly every theory of liquids. In particular, Tiunlirz^^ and 



56 Regnault, 1. c. (1862). 



57 Tumlirz, Sitz. k. Akd. Wiss. Wien, 118, 1-39 (1909). 



