380 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



Discussion of the Data. 



TABLE V. 



VoLrME OF Hg at 0° AND 22° 



These data may be used in mapping out the p-v-t surface, and for 

 giving certain information about the thermodynamic behavior of liquid 

 mercury under pressure. The proportional changes of volume given 

 above were calculated in the usual way, by taking the volume under 



atmospheric pressure and at the 

 temperature in question as the unit 

 volume. To map the p-v-t surface, 

 correction must be made for the 

 change of volume with temperature 

 at atmospheric pressure. Thus, if 

 the volume when p = 1 and ^ = 0° 

 is taken as unity, the values given 

 by the process just mentioned for Ay 

 at 22° must be corrected by multiply- 

 ing by the ratio of the volume at 22° 

 and j!? = 1 to the volume at 0° and 

 /> = 1. The actual volume under 

 different pressures, and at 0° and at 

 22° is given in Table V. In this the 

 value for the total change of volume 

 between 0° and 22° was taken as 

 0.00398, as given by the most recent 

 work of Callendar and Moss ^i on the 

 expansion of mercury. It appears from 

 their work that the mean coefficient of 

 expansion at 0° is 0.0001805, while 

 the mean coefficient between 0° and 

 100° is 0.0001817. This gives for 



m. 



the value O.O724, which is 



evidently beyond the accuracy of this 

 work. That is, for the present pur- 

 pose, over the temperature and pres- 

 sure range involved, the isothermals may be assumed to be equally 

 spaced. This is sufficiently accurate at atmospheric pressure, and all 

 our experience with other more compressible liquids would lead us to 

 expect it to be all the more nearly true at higher pressures. 



^1 CaUendar aud Moss. Proc. Roy. Soc. Lon., A, 84, 59^-597 (1911). 



