468 



SCIENCE PROGRESS 



tremors and the special disadvantage of having the torsion 

 balance in a vacuum " ; and further to conclude that there is a 

 temperature effect of gravitation. " When one large mass 

 attracts a small one, the gravitative force between them in- 

 creases by about 1/500 as the temperature of the large mass 

 rises from, say, 15 C. to 21 5 C. At present the result is 

 provisionally stated as being + i'2 x io -6 per centigrade 

 degree ; but the readings are not steady enough to justify the 

 statement that there is a linear relation connecting the gravita- 

 tion constant and temperature." 



Dr. Shaw, in a short review of the previous work on the 

 constant of gravitation, points out that, though much of it 

 yields no evidence one way or the other on this point, yet a part 

 of it does lend some small weight to the view that there is a 

 positive temperature effect for gravitational attraction. 



PHYSICAL CHEMISTRY. By Prof. W. C. McC. Lewis, M.A., D.Sc, 

 University, Liverpool. 



Electrolytic Dissociation {continued). — Having considered the 

 behaviour of HC1, it is of interest to compare it with that 

 exhibited by KC1, especially since KC1 is supposed to be more 

 normal in its behaviour in respect of ionisation-values as 

 given by conductivity measurements. Accurate electromotive 

 force measurements of concentration cells, involving KC1, 

 have been recently carried out by Maclnnes and Parker 

 (/. Amer. Chem. Soc. 37, 1445, 191 5) at 25° C. which agree 

 well with those carried out by Jahn at 18 C. The following 

 table contains the values of a and 7 for this substance. The 

 assumption is made that at o'ooiN, a = 7. 



Activity Coefficients and Conductivity-viscosity Ratios 

 of KC1 at 18° C. OR 25°C. 



These results show that with KC1, just as in the case of 

 HC1, the activity coefficient decreases much more rapidly than 

 the conductivity ratio, a being 15 per cent, lower than 7 in a 



