446 Dr. R. D. Kleeman on 



Now the writer has shown * that the radius of the sphere 

 of action of the force of attraction of different molecules is 

 the same fraction of their radius at the absolute zero. He 

 had also previously shown j" that the attraction between two 



molecules is given by the expression (X \/m^) 2 ^</>(^, j3h 



where 2) V^ m i denotes the sum of the square roots of the 

 atomic weights of the atoms composing a molecule, z is 

 their distance of separation, x c is their distance of separation 



T 



at the critical state, and P = m where T denotes temperature. 



From this it follows that at corresponding states, <fi I — , ft \ 



will be the same for all liquids, and the radii of the sphere 

 of action of different molecules at corresponding temperatures 

 therefore the same fraction of their radii at the absolute zero. 

 We shall therefore be on much safer ground if we compare 

 values of <r 1 or cr 2 at corresponding states. 



Let the relative values of o^ 2 be determined for a number 

 of different molecules and also their molecular volumes in 

 the liquid state, both at corresponding temperatures. Then 



y 

 if V denotes the molecular volume, the ratio — -» will be the 



same for all liquids if the molecules are spherical in shape, 

 for V is then proportional to o^ 3 . But if it is not spherical 

 in shape the ratios are not necessarily the same, and we shall 

 be nearer the truth in supposing the molecule an oblate 



Y 



spheroid of which — 5 is proportional to an axis of the 



*! y y o- 



generating ellipse. If we denote — % ^7 a 2> ^ en — 3 = ~ 



A set of calculations of this nature has been carried out, and 



the results are contained in Table I. They correspond to 



349*7 



^— — - T . The relative values of cr x were calculated bv 



oob'l , N19 J 



/ 711V \ / 



means of the equation cr 1 = ( j — ) , where m denotes the 



molecular weight, v the velocity of translation of a molecule, 

 and rj the coefficient of viscosity. In this equation, v was 



/t y/ 2 



put proportional to I — j , and then a x is proportional to 

 y 2 . The coefficient of viscosity corresponding to the 



* Phil. Mag. p. 480, June 1910. 



f Phil. Mag. pp. 788-792, May 1910. 



