BRIDGMAN. — MERCURY UNDER PRESSURE. 



421 



The rise ofAE to a probable maximum is the most interesting feature. 



The course of this curve is to be explained by the increasingly rapid 



drop of A r at high pressures, this drop finally becoming more rapid 



dp 

 than the increase in -j-- and in the absolute temperature. 



ar 



TABLE XII. 



Change of Latent Heat on the Freezing Curve of Hg. 



It will be noticed here, as for the change of volume, that the curve 

 does not give the usually quoted value for the heat of transformation 

 at— 38°.85, but here also it seems that there is considerable chance 

 for error in the previous value. The value always given is 2.82, which 

 was obtained by Person *3 in 1847. As far as can be discovered, this 

 is the only determination of this quantity which has ever been pub- 

 lished. Person's method consisted essentially in dropping the frozen 

 mercury at a temperature of about —42° into the water or turpentine 

 of a calorimeter, and noting the fall of temperature. The usual cor- 

 rections for radiation and the heat capacity of the vessel were applied. 

 The actual heat given to the calorimeter was the sum of the heat 

 given out by the solid in cooling to the transformation point, the heat 

 of transformation, and the heat of the liquid in warming to the tem- 

 perature of the calorimeter. The value Cp = 0.0,333 was assumed to 

 hold for the liquid over the temperature range. This is probably 

 nearly correct, but the assumption that Cp for the solid is the same as 



« Person, Ann. de Chim. et Phys., 24, 257-264 (1848). 



