116 On the Internal Pressure of a Liquid. 



It has been shown, however, that between the critical 

 point and higher pressures the equation does not apply so 

 well as that of van der Waals. At very low temperatures 

 presumably the inverse fourth power law would be more 

 closely obeyed, but this cannot be tested directly down to 

 very low temperatures owing to solidification of the liquid — 

 unless solidification or crystallization is itself occasioned by 

 the molecules arranging themselves under the inverse fourth 

 power attraction into definite positions which give rise to 

 crystalline structure. 



Summary. 



1. The minimal values of the internal pressures of a large 

 number of liquids at 0° C. have been calculated employing 

 Young's data. 



2. The Obach-Walden relation regarding the approximate 

 direct proportionality between the internal pressure and the 

 dielectric constant has been shown to follow from the hypo- 

 thesis that molecular attraction is electromagnetic, not electro- 

 static in nature. 



3. As a corollary to (2) it has been shown that the sub- 

 stances with the larger internal pressures possess corre- 

 spondingly smaller values for the permeability. 



4. Pascal's relation, viz. that the product of the suscepti- 

 bility into the specific volume is a constant for a given 

 substance, is shown to involve constancy of orbit for the 

 revolving electrons, and this taken in conjunction with Bohr's 

 assumption of constant angular momentum leads to the con- 

 clusion that the vibration frequency of the absorption bands 

 in the visible and ultra-violet should be the same for both 

 liquid and vapour, a conclusion which is approximately but 

 not strictly in accordance with experiment. 



5. The effect of temperature in partially destroying the 

 orientation of the molecules appears to alter the inverse 

 fourth power law to the inverse cube as expressed in Dieterici's 

 equation 



(i>+^)0-&)=RT. 



In conclusion I wish to express my indebtedness to Mr. 

 James Rice, M.A., Lecturer in Physics in this University, 

 for his helpful criticism and suggestions in regard to this 

 paper. 



The Muspratt Laboratory of Physical and Electrochemistry. 

 The University of Liverpool, February 1914. 



