PROCEEDINGS OF THE AMERICAN ACADEMY. 



I. Introduction. 



The experimental material of this paper consists of direct measure- 

 ments of the ^•olume of twelve liquids at different temperatures and 

 pressures. The pressure range is from atmospheric pressure to 

 12000 kgm. per sq. cm., and the temperature range from 20° to 80°. 

 The measurements were made at enough points to determine the 

 volume at any pressure and temperature. These data are presented 

 in the first part of the paper. The second part of the paper contains 

 a discussion of a number of quantities of thermodynamic significance 

 which have been computed from the data of the first part. The 

 discussion is concerned only with the more important thermodynamic 

 properties, namely the isothermal compressibility, thermal expansion, 

 work of compression, heat of compression, change of internal energy, 

 and the specific heats at constant pressure and constant volume. 



Apparently the only other work of similar character at even com- 

 paratively high pressures is that of Amagat,-^ published in 1893. 

 Amagat measured the volume of twelve liquids up to 3000 kgm. and 

 between 0° and 40° or 50°. Beside the volume he tabulated the 

 compressibility, dilatation, and pressure coefficient for some of the 

 liquids, but the tabulation was by no means systematic or complete. 



It is hoped that the material in this paper will afford the means for 

 a renewed attack on the problem of the nature of the mechanism of 

 a liquid. Theoretical speculation has been concerned hitherto chiefly 

 with phenomena of liquids at low pressures, such as the latent heat 

 of evaporization or the surface tension. At high pressures there are 

 effects of another order, just as significantly descriptive of the internal 

 mechanism, but as yet hardly touched by speculation. The data of 

 this paper cover four times any previous pressure range, and should 

 be sufficient to show the general nature of high pressure effects. 

 Furthermore, the systematic presentation of different thermody- 

 namic properties should afford different points of view for the attack. 



The actual state of affairs at high pressures was found to be exceed- 

 ingly complicated, contrary to what we might expect. We might 

 suppose that the molecules would become so closely packed at high 

 pressure as to allow less variety in their response to external changes, so 

 that a liquid would approximate to a solid, in which compressibility 

 and expansion change only slightly with pressure and temperature. 

 A hypothesis of this character, backed up it is true by some experi- 



1 Amagat, Ann. Chim. et Phys., 29, 68-208 (1893). 



