384 



PROCEEDINGS OF THE AMERICAN ACADEMY. 





273 X O.O724 



= - O.O5655, 



Cp being expressed in ergs per cm.* and p in dynes per cm, 

 pressed in gm, cal. and kgm./cm.* this becomes 



Ex- 



m,- 



0.06154. 



This variation is so small that 

 over the pressure range here. 



TABLE VI. 



Cp AND Cv FOR Hg at 0°. 



we may assume it to remain constant 

 This would give a total change of Cp 

 of only 1/4 per cent for 7000 kgm. 

 Probably the change is actually 

 less than this. Table VI. shows the 

 values of Cp calculated with this 

 assumption, and also the values of 

 Cp found from the already calculated 

 values of Cp— C^. It is seen that while 

 Cp decreases with pressure, C^ in- 

 creases, the increase being more rapid 

 than the decrease. In computing the 

 date of the table, the value of Barnes 

 and Cooke ^^ for Cp at atmospheric 

 pressure and 0° was used, 0.03346 gm. 

 cal. per gm., or 0.4549 gm. cal. per 

 cm.^ 



There are several other quantities 

 of interest that may be deduced from 

 the given data. One of these is the 

 difference between the isothermal and 

 the adiabatic compressibilities. We 

 have the thermodynamic formula 



\dpjr \^pj<t> 





5 J; 



The results are shown in Figure 12. The adiabatic compressibility, 

 therefore, on the isothermal t = 0°, decreases less rapidly than the 

 isothermal compressibility. 



Intimately connected with the adiabatic compressibility is the tem- 

 perature effect of compression. For this we have 



" Barnes and Cooke, Phys. Rev., 16, 65-71 (1903). 



