420 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



It is not claimed, however, that the absolute values at the high pres- 

 sures have quite so much accuracy as this self-consistency would in- 

 dicate, since probably the correction for the distortion of the upper 

 cylinder leaves room for greater uncertainty than this. 



S3.20 



S 



g3.IO 



CJ> 



3.00 



^2.90 



H 

 Z 2.80 



32.70 



-40 -30 -20 -10° 0" 10° 20° 

 TEMPERATURE 



Figure 23. The latent heat of solid mercury as a function of the equilib- 

 rium temperature. 



It is gratifying to notice that the point determined at atmospheric 

 pressure by an entirely different method agrees perfectly with the 

 points found above, making the accuracy of both determinations very 

 probable. 



P'rom these data the latent heat of transformation may be found at 

 every point of the melting curve by Clapeyron's equation, 



All= tAv 



dp 



All was calculated from this equation at intervals of 10° from — 40° 



dp 

 to -f 20°. -J- was found by adding to the constant value 196.4 kgm. 



UT 



per degree the correction found from the graphically constructed slope 

 of the curve showing the departure of the curve from linearity. The 

 results of this graphical construction are shown in Figure 22. The ab- 

 solute zero in the calculation was taken as — 278°.l C. The results in 

 mean gm. cal. per gm. of mercury are shown in Figure 23 and Table XII. 



