CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL 

 LABORATORY, HARVARD UNIVERSITY. 



MERCURY, LIQUID AND SOLID, UNDER PRESSURE. 



By p. W. Bridgman. 



Presented by G. W. Pierce, Oct. 11, 1911. Received Oct. 6, 1911. 



Introduction. 



This paper is an attempt to present for the liquid and solid phases 

 of a single simple substance, mercury, data corresponding to the data 

 which have been collected for the gaseous and liquid phases of many- 

 substances. These latter data are the relations connecting temperature, 

 pressure, and volume of the gas together with the changes involved 

 when the gas passes to the liquid state. Out of these data have come 

 the theories of the molecular structure of gases and vapors, and the 

 various relations connecting the gaseous with the liquid phase, of 

 which the theory expressed by the equation of van der Waals is the 

 best known. The corresponding work for the liquid and solid phases, 

 that is, the mapping out of the pressure- volume-temperature surface of 

 the liquid and the determination of the quantities involved in the 

 change from the liquid to the solid state, has never been done. As a 

 result, the theory of liquids is entirely undeveloped, and the theory of 

 the relation between liquid and solid hardly begun. For instance, the 

 fundamental question as to the existence of a critical point for the 

 liquid-solid states analogous to that for the vapor-liquid is as yet 

 unsettled. 



The apparent reason for this neglect of the thermodynamic data for 

 the liquid and solid is merely experimental difficulty. Whereas for a 

 vapor the critical pressure never exceeds a few hundred atmospheres, 

 the pressures involved in a corresponding study of the liquid-solid 

 phases are of the order of tens of thousands of atmospheres. These 

 pressures are so high as to tax to the utmost the tightness of every 

 joint and the strength of the steel vessels. In this present work it 

 has been found possible by a special packing device, which secures ab- 

 solute freedom from leak, and by the use of the highest grades of steel 



