BRIDGIVIAN. — MERCURY UNDER PRESSURE. 351 



Change of State of the Transmitting Liquid 413 



Measurements of Piston Displacement 413 



Pressure Measurements 414 



The Data 414 



Methods of Computation 416 



The Latent Heat — New Value at Atmospheric Pressure . 420 



Recomputed Value for the Specific Heat of the SoUd . 422 



Rough Value for the Compressibility of the Solid .... 423 



d. Change of Volume at Atmospheric Pressure 423 



Probable Error in the Previous Results 424 



The New Method 424 



The New Value 428 



Recomputation of Quantities depending on the Value for 



the Change of Volume 428 



Density of the Sohd 428 



Dilatation of the Solid 428 



Direct Experimental Evidence on this Point .... 429 



e. Subcooling and Superheating 429 



IV. Conclusion 431 



Bearing on the Theory of Liquids 432 



Bearing on the Theory of the Change of State, Liquid-Solid . . 433 



Significant Behavior of Latent Heat and Internal Energy . . . 435 



V. Summary 437 



The P-V-T Surface of Mercury. 

 The Coynpressibility of Liquid Mercury. 



This first section of the paper is devoted to a determination of the 

 compressibility of mercury at 0° and at 22°. The question of exper- 

 imental method is important, since the compressibility of mercury is 

 small, and there are various effects which make determinations at high 

 pressures much more difficult than over a smaller pressure range. The 

 section comprises a discussion of the method and the various errors to 

 be avoided, an experimental determination of the compressibility of 

 the steel, which was needed in the computations, the actual data for 

 the compressibility of mercury, with a somewhat detailed discussion of 

 the way of adjusting them so as to give the best results, and finally, a 

 calculation from the data of the change of the various physical proper- 

 ties of mercury under pressure. 



One of the chief difficulties in the experimental investigation of the 

 properties of bodies under pressure is the determination of the correc- 

 tion for the distortion of the containing vessel. This is particularly 

 true in the case of compressibility, where the change of shape and vol- 

 ume of the containing vessel is an effect of the same kind as that being 

 measured, and may often constitute a large part of the total change. 



