JH4 



MR. W. R. BOUSFIELD AND DR T. M. LOWRY ON THE ELECTRICAL 



oolution* or by errors introduced in standardising the solutions by titration. We 

 have therefore redetermined the conductivities at 18 C., and although our electrical 

 measurements are probably not so accurate as those of KOHLRAUSCH, we consider 

 that the purity and accuracy of our solutions and the increased number of observa- 

 tions combine to render our measurements at 18 C. more 

 reliable than those previously recorded. 



(1.) The Solutions used for the electrical measurements 

 were similar to those employed in measuring the density, and 

 indeed in one series of dilutions the same solutions were used 

 for measuring the two properties. As it was likely that the 

 conductivity would be influenced more than the density if the 

 alkali should become partially neutralised by carbonic or 

 silicic acid, special care was taken to maintain as far as 

 possible the original purity of the solutions. The solutions 

 used in measuring the conductivity from 50 per cent, to 

 20 per cent, were kept in platinum vessels and only allowed 

 to come into contact with the glass of the electrode that was 

 introduced in measuring the conductivity. The solutions 

 below 20 per cent, were made up from standard solutions 

 which had been kept in platinum or stored in a glass bottle 

 as 50-per cent, solutions during periods ranging from a few 

 days up to two months, but as the density remained 

 unchanged at the end of ten weeks, and the maximum 

 conductivity measured at the end of five months was within 

 O'l per cent, of the value obtained before transferring to the 

 glass bottle, it is believed that no appreciable fouling had 

 resulted from the contact of the viscous 50-per cent, solution 

 with the glass. 



(2.) The Conductivity Vessel. No difficulty is experienced 

 in designing a conductivity apparatus of low resistance 

 capacity in which the liquid is allowed to come into contact 

 only with platinum surfaces, but it is very difficult, perhaps 

 even impossible, to design a simple apparatus of this kind in 

 which the resistance capacity is sufficiently large to give 

 satisfactory measurements with solutions of high conductivity. We were able, how- 

 ever, to effect a very satisfactory compromise by making use of the platinum vessel 

 already described and introducing into it an electrode shielded within a glass tube 

 of suitable shape. The total area of glass in the electrode was comparatively small, 

 and 300 cub. centims. to 400 cub. centims. of solution was used for each observation. 

 Under these conditions the fouling of the solution by contact with the glass of the 



* See footnote, p. 287. 



Fig. 5. 



