230 



Dr. It, D. Kleeman on 



molecule, N is the number of molecules in unit volume 

 at atmospheric pressure, and L is the mean free path of a 

 molecule. Since N has the same value per unit volume for 

 all gases at the same temperature and pressure, the diametrical 

 sections of any two molecules are to one another as the cor- 

 responding values of Q. The tables contain also the values 

 of S?n 1/3 , the values of ra 1/3 used for their calculation being 

 given at the head of Table I. The last column of each table 

 gives the ratio of Q to 2«i 1/3 . 



Table I. 

 Cube roots of the atomic weights of a number of atoms : 

 H = l, C = 2-29, N = 2-4l, = 2-52, Fl = 2'67, S = ?>*18, 

 01 = 3-29, Br=4\31, I = 5'03, Hg= 5*85. 



Gas. 



Q. 



^ 1/3 



Q 



^ 1/3' 



CO 



18,700 

 27,000 

 18,600 

 27,100 

 19,200 

 17,400 

 22,200 

 43,500 

 49,300 



4-81 

 733 

 4-82 

 734 

 493 

 5-04 

 6 29 

 1310 

 12-87 



3,888 

 3,684 

 3,859 

 3,693 

 3,895 

 3,452 

 3,530 

 3,321 

 3,830 



co 9 : 



N, 



N 2 



NO 



0, 



CHj 



2 H 6 



2 H 6 C1 





H 2 



9,900 

 24,900 

 42,500 

 40,100 

 43,900 

 37,900 



2 00 

 541 



8-58 

 8-58 

 942 

 822 



4,950 

 4,603 

 4,953 

 4,673 

 4,660 

 4,610 



NH 3 



2 H 4 



CH 3 C1 



C N 



SO„ 





HCi 



25,100 

 38,800 

 24,900 

 29,300 



429 

 6-58 

 4-52 

 5-18 



5,851 

 5,896 

 5,509 

 5,657 



Cl 



h"o 



H 2 S 





If the atoms of a molecule all lie in a plane, then, as Meyer 

 has shown in his ' Kinetic Theory of Gases,' pp. 304-309, 

 the cross-section of a molecule ought to be approximately 

 equal to the sum of the cross-sections of the component atoms. 

 The cross-section of a molecule should therefore be an additive 

 quantity relating to its atoms, and this Meyer finds to be, 

 approximately the case. If, further, the shape of the atom 

 is spherical and its volume proportional to ra 1/2 , the cross- 

 section of a molecule will be proportional to 2w 1/3 , and the 



ratio 



Q 



will be constant. This, as will be seen from the 



SmV3 

 tables, is to a certain extent realized 



