ON THE HALOGEN HYDEIDES AS CONDUCTING SOLVENTS. 



147 



SUMMARY. 



With the exception of Nos. I and 4, which unfortunately were lost, all the 

 experiments which have been made are given in the tables. The transport number 

 of each substance has been measured at two concentrations, the more conceTitrated 

 solution usually containing about twice as much solute as the other. It will be seen 

 that the cation transport number is always increased by increase of concentration and 

 that the amount of disagreement between parallel experiments, although in some 

 cases approaching 10 per cent., is never sufficient to leave any doubt as to the influence 

 of change of concentration. This change from analogy with aqueous solutions 

 indicates an increase in the complexity of the cation as the solution becomes stronger, 

 but the measurements of conductivity and of the molecular weight, which are given in 

 Part II., do not appear to confirm this conclusion. The significance of the change 

 will be discussed in Part IV. 



A special significance is to be attached to the results of Series 2, for the following 

 reasons : In the foregoing description of the method of analysis it has been explained 

 that after the solution was transferred to the absorber the hydrogen bromide was 

 allowed to evaporate and to become dissolved in the water. During the evaporation 

 the temperature of the liquid in A gradually rose until finally it reached that of the 

 atmosphere, when the liquid which remained was a saturated solution of hydrogen 

 bromide in ether. 



At this stage little or no decomposition occurred in a solution which had not been 

 electrolysed, or in a dilute solution which had, but in the case of the cathode portion 

 of a concentrated electrolysed solution the decomposition which occurred was sufficient 

 to give results so discordant as those tabulated in Series 2. This behaviour seems to 

 indicate the formation at the cathode of some extremely unstable substance during 

 the electrolysis of these solutions, and it is possible that a compound is formed by the 

 union of two or more discharged cations by a reaction similar to that by which 

 persulphuric acid results from the electrolysis of sulphuric acid. 



u 2 



