BRIDGMAN. THERMODYNAMIC PROPERTIES OF LIQUIDS. 101 



tive specific heat is impossible. The only case where this condition 

 comes anywhere near making trouble is for amyl alcohol. The curve 

 for 80° shows a decrease of Cp of 21 kgm. cm. The data for atmos- 

 pheric pressure are discordant, but 25 kgm. cm. seems to be a fair aver- 

 age value at 80°. This would mean that the specific heat at 80° and 

 12000 kgm. is only 4 kgm. cm., about one sixth its initial value. It 

 is evident that the reversal in the efl^ect must come speedily. 



Figure 99 for the average change of C^ over the entire temperature 

 range for the twelve liquids shows much less variation from liquid 

 to liquid than one might expect from the irregular variations at the 

 different temperatures. The curves in general all show the same 

 characteristics ; at first a decrease of specific heat and then an increase 

 at higher pressures. The first minimum has already been commented 

 on in another connection. Beyond this minimum in Cp (maximum 

 on the curves) there is in general a continuous increase with rising 

 pressure, although there are several cases where Cp decreases again 

 slightly at the highest pressures. The three halogen compounds are 

 exceptional (and also acetone) for the rather large increase of Cp with 

 rising pressure. The increase is greater for the heavier members of 

 the series. 



The data of the previous paper on water show the same behavior, 

 a minimum in Cp for all temperatures (except at 0° where the curve 

 is broken off by the freezing) and then an increase with still further 

 increasing pressure. The pressure for the minimum is higher than 

 for these twelve liquids because of the abnormal behavior of water 

 at low pressures. 



So far as is known to the author, these are the only measurements 

 from which an attempt has been made to find the specific heat at 

 high pressures. The probable behavior of the specific heats does not 

 seem to have been suspected. Thus Tumlirz deduces from his em- 

 pirical equation for liquids that both the specific heats decrease with 

 rising pressure. For water, Tumlirz finds the limiting value of Cp 

 for infinite pressure to be about 0.5 gin. cal. He does not compute 

 it for the other liquids. We see from the above that we are to expect 

 for all liquids an ultimate increase instead of a decrease with rising 

 pressure. 



Specific Heat at Constant Volume. — The specific heat 

 at constant volume is shown in Folder VII, the curves of the dif- 

 ferent liquids at different temperatures in Figures 100 to 111, and 

 the collected averages for all the liquids in Figure 112. The treat- 

 ment of these curves is the same as for C„. 



