320 The Halogen Hydrides as Conducting Solvents. 



" The Halogen Hydrides as Conducting Solvents. Part III. The 

 Transport Numbers. Preliminary Notice." By B. D. 

 STEELE. Communicated by Sir WILLIAM KAMSAY, K.C.B., 

 F.K.S. Received November 29, Read December 15, 1904 



In continuation of this investigation* the transport numbers of 

 several substances have been measured when dissolved in liquefied 

 hydrogen bromide. 



The substances selected were ethyl ether, acetone, methyl hexyl ketone 

 and triethylammonium bromide, the first two of which have been 

 shown to form compounds with hydrogen bromide. 



As a preliminary to the main series of experiments the validity of 

 Faraday's law for solutions in hydrogen bromide was tested, and the 

 law found to hold within the limits of the errors of experiment of 

 the method employed, which consisted in the direct comparison of the 

 amount of hydrogen evolved during the electrolysis of various substances 

 in hydrogen bromide solution, with the weight of silver deposited at 

 the cathode of a silver voltameter. 



In one experiment the amount of hydrogen evolved was 19'7 c.c., 

 the hydrogen equivalent of the silver deposited being 19 '8 c.c. 



The transport numbers were determined by the method of Hittorf 

 at a temperature of - 81. 



Great difficulties were experienced in carrying out the analyses with 

 the required degree of accuracy, and the method of analysis finally 

 found to be successful was one depending on the direct weighing of 

 the whole solution to be analysed in a specially constructed absorbing 

 apparatus, and the subsequent determination of the hydrogen bromide 

 by titration, the difference giving the amount of dissolved substance 

 contained in the solution taken. 



The following mean values were found for the transport number of 

 the cation : 



n = concentration expressed in gramme-molecules per litre. 

 P = cation transport number. 



The experiments show that the cation transport number increases 

 with increasing concentration, and that the ether (or acetone, &c.), 

 functions as the cation or as a component part of it. 



* ' fr-'ee ' Roy. Soc. Proc.,' vol. 73, pp. 450455. 



