322 The Halogen Hydrides as Conducting Solvents. 



This behaviour is manifested by, amongst others, a solution of 

 hydrocyanic acid in hydrogen chloride, which gives the following 

 values for v and Ki/ 2 . 



v = 41-4 21-6 14-1 10-2 3-12 2'56 1-79 1-23 



aK = KV 2 = 2-11 1-96 1-40 1-20 1-15 1-15 1-04 0'94 



From these it will be seen that according to the foregoing explana- 

 tion, a increases with dilution, a variation which is that required by 

 the ionic theory. 



In the case of triethylammonium chloride dissolved in hydrogen 

 chloride a varies to a much greater extent, as the following figures 



show 



v = 37-0 16-1 9-43 6-13 4*25 3*64 



Kv 2 = aK = 66-7 43-7 34'3 31 '6 28'5 28-0 



In both the foregoing cases n is found to be equal to 2, or two 

 molecules of solute combine with the solvent to form the dissociating 

 substance. 



In other cases n = 3, or three molecules combine with the solvent, as 

 for example, acetone dissolved in hydrogen bromide, for which solution 



v = 8-33 5-00 3-23 1'64 1'35 1-07 0'75 

 Ki/ 2 = OLK = [7-00] 8-50 8-1 6-3 5-9 4-9 3-2 



Here again the increase of a with dilution is clearly indicated. 

 For substances dissolved in water n 1 and K = /A W , and since 

 KV = p,, the equation K = aKv n becomes 



and for purposes of comparison with the foregoing the corresponding 

 numbers for v and KV are given for a salt. (Cd S0 4 ) dissolved in 

 water. 



v = 100 50 20 10 5 2 1 

 KV = aK = 71-8 61-8 49-6 42*4 36'2 29*1 23-8 



Confirmation of these views is afforded by the results of the molecular 

 weight determinations, which show that in many instances the 

 molecular weight is greater than the normal, indicating that associa- 

 tion has taken place to some extent. 



