232 



Dr. R. D. Kleernan on 



The deviations from constancy are more likely dne to the 

 values of Q not giving the true relative values of the sections 

 of the molecules, than to the atoms not being spherical in 

 shape, or their volumes not being proportional to ra 1/2 . The 

 value of Q must obviously include a certain amount of space 

 not occupied by the atoms, especially that situated near the 

 centre of the molecules. The amount of included space in a 

 molecule will depend on the arrangement of its atoms. 

 Probably the variation of Q with temperature is largely due 

 to a variation of the amount of unoccupied space included 

 in Q. 



The values of =rH« in Table I. show a distinct tendency 



to fall into three groups, the values of each group being 

 approximately constant. Each group probably corresponds 

 to a certain arrangement of the atoms corresponding to which 

 a certain proportion of external space is included in Q. 



The same tendency is exhibited by the values in Table II. 

 The values belonging to the same chemical group are approxi- 

 mately constant. This is best shown by the alcohols and 

 esters. In a few cases two values of Q for the same vapour 

 are given in the table corresponding to different observers. 

 The large differences that sometimes exist between the results 

 of different observers, which are probably due both to errors 

 of experiment and different methods of measurement, suggests 



Q 



that the deviations from constancy of the ratio ^r 

 a certain extent due to erroneous values of Q. 



Table III. 



1/3 



are to 





Q. 



x. 1/3 



Q 



V 1/3 



CLELBr, 



68,000 



63,000 

 74,000 

 49,900 

 74,600 

 42,300 

 51,400 



1720 

 1618 

 16-22 

 1461 

 23-19 

 10-32 

 5-85 

 1170 



3,954 

 3,894 

 4,562 

 3,415 

 3,224 

 4,100 

 8,788 

 4,391 



C 2 H 4 ClBr 



CHBr 3 



CJBM 



C 4 H q I 



CH 3 I 



fHg 



1 H^ 





Q 



for a few molecules 



Table III. contains the ratio of ^ 



Zm 1 ' 3 



which contain heavy atoms. It will be seen from the table 

 that if the mercury molecule is taken as monatomic the value 



