456 STUDIES IN GENERAL PHYSIOLOGY 



3. Can we now say that in these experiments we are deal- 

 ing only with the effects of the hydrogen ions? In order 

 to decide this question, we must see which fraction of the 

 molecules of acid is dissociated at the dilution employed. 

 If we designate that fraction of the molecules which are 



dissociated by a, then, as is well known, a = J-L. , where 



fj> v represents the molecular conductivity of the electrolyte at 

 the dilution z>, ^^ the molecular conductivity at infinite 

 dilution. 



" According to Ostwald, 1 the speed of migration of the H 

 ions at 25 =325, that of the Cl ions = = 70.2. According to 

 Kohlrausch's law /^-^ is for HC1 therefore = 395. In the 

 same way we find for HNO 3 , p^ - = 390. According to 

 Kohlrausch, the speed of migration of H ions at 18 =290. 

 That of SO 4 can be determined indirectly as about 132. 2 

 /-IJQ is therefore at this temperature 712 for H 3 SO 4 . 



When r==200, /* for HC1 = 377, for HNO 3 ==377. At 

 18, and when T =333, p v for H 2 SO 4 , according to Kohl- 

 rausch, - = 600.2. In our experiments V =400. For V 

 400, ^ v would lie between 600 and 610. 



In our solutions, therefore 



a = = 0.95 for HC1 (25'); 



a = ^ = 0.96 for HNO 3 (25); 



a = nf = 0.8 (inaccurate) for H 2 SO 4 (18). 



The effect which the presence of NaCl has on the dis- 

 sociation of the acids is neglected in these values. 



If we study the figures somewhat more closely, we see 

 that they are not far removed from unity; that, in other 

 words, about 95 per cent, of the hydrochloric and the nitric 

 acid molecules have dissociated into ions, and something less 



1 OSTWALD, Lehrbuch, 2d ed., Vol. II, p. 675. 



2 KOHLRAUSCH, Wiedcmann's Annalen, Vol. L. 



