BEIDGMAN. — MERCURY UNDER PRESSURE. 



419 



the correction for the elastic deformation of the upper cylinder are 

 both applied. In the second and finally corrected column, the addi- 



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TEMPERATURE 



Figure 21. Shows the change of volume and of internal energy on passing 

 from the Uquid to the solid. The change of volume curve was directly observed, 

 and the experimental points are indicated. The change of energy curve was 

 calculated from the other data. 



tional correction for the variation of room temperature is applied. 

 The sign of this correction changes with the direction of variation. 

 As appears from the figure, these points are self-consistent, lying on a 



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 TEMPERATURE 



Figure 22. Shows the slope of the freezing curve as a function of the 

 equihbrium temperature. 



smooth curve to at least the order of accuracy given above, 1 part in 

 2500, except the point at 9° which is only 1/10 per cent out. The 

 total displacement of the piston during freezing was about 0.2 inch, 

 the quantity of mercury used being in the neighborhood of 350 gm. 

 To obtain the above accuracy, therefore, it was necessary to take ad- 

 vantage of the utmost capacity of the micrometer, making all the 

 readings to 0.0001 inch. That the single measurements do enjoy this 

 degree of accuracy is made evident by a later very much enlarged 

 figure drawn for the purpose of showing the impossibility of subcooling. 



