﻿

Balance Method of Measuring X-Rays. 1159 



Better agreement is scarcely to be anticipated, since the 

 values of P for any liquid are not known to any degree of 

 accuracy ; P for benzene, for example, varying from 1300 

 to 3810 atmospheres, according to the method employed for 

 its evaluation (Hildebrand, J. A. C. S. xli. p. 1072 (1919)). 

 The parallelism between the two sets of determinations and 

 the decrease in the molecular relaxation period or increase 

 in molecular "sensibility" with increasing polarity is, how- 

 ever, clearly marked. 



Summary. 



The rate of penetration of a liquid into a fine capillary 

 under its own forces is shown to be expressed by the 



2 7? O?*^ 



relationship t=- - as 2 — q— log sc. For relatively large 



capillaries the penetration coefficient is i/ J~. 



The experimental determination of the coefficient is shown 

 to agree with the calculated values. In the case of mixed 

 solvents the dynamic surface tensions and not the static 

 values are probably the governing factors. 



The reciprocal of the penetration coefficient is proportional 

 to the square root of the period of molecular relaxation as 

 defined by Maxwell, and on analogy with reactions in the 

 solid state is probably important in reactions taking place in 

 liquid media. 



The writer is indebted to Mr. R. L. Huntingdon for 

 assistance in the experiments detailed in this paper. 



Chemical Department, 



Cambridge University, 

 June 5th, 1922. 



CIX. On a Balance Method of measuring X-Rays. By 

 Professor S. Russ, JJ.Sc, and L. H. Clark, M.Sc, 

 Physics Department, Middlesex Hospital *. 



I^HE frequent and prolonged running of X-ray tubes 

 calls for some convenient method of recording con- 

 tinuously the intensity of the X-radiation emitted during the 

 period of excitation. The balance method described below 

 indicates at any instant this intensity and is capable of 

 giving a continuous record of it. It is suitable for the 

 measurement of the ionization produced by a powerful beam 

 of X-rays. 



* Communicated by the Authors, 



