2/0 Conductivity of Aqueous Solutions. Part VIII. 



The great effect of temperature in reducing the ionization of this acid 

 will he apparent from an inspection of these constants or of the ionization 

 values themselves given in table 114. 



The values given for sulphuric acid in tables 114 and 115 show the per- 

 centage of the total hydrogen which exists as hydrogen-ion under the two 

 limiting assumptions that the acid dissociates on the one hand only into 

 hydrogen-ion and sulphate-ion and on the other only into hydrogen-ion 

 and hydrosulphate-ion (HSCXf). It will be seen that the two limits do 

 not differ greatly from each other, except at the highest temperatures, 

 and therefore that the uncertainty as to the hydrogen-ion concentration, 

 which is really the most important datum relating to the acid, is not very 

 large. It is evident that this hydrogen-ion concentration decreases rapidly 

 with rising temperature ; for example, at 0.08 normal from about 66 per 

 cent at 18 to about 45 per cent at 100 and about 30 per cent at 30G, if 

 the mean values be taken. 



By this hydrogen-ion concentration, however, not much light is thrown 

 on the extent to which the two stages in the dissociation take place. It 

 might seem that additional information in regard to this could be derived 

 from the transference determinations made at 11, 23, and 96 by Bein* 

 and between 8 and 32 by Tower.f But calculation shows that the trans- 

 ference numbers of the cathion calculated under the two limiting assump- 

 tions of dissociation only into hydrogen-ion and sulphate-ion and of disso- 

 ciation only into hydrogen-ion and hydrosulphate-ion (HSG 4 ~) do not 

 differ from each other by much more than the possible experimental error 

 or than the error arising from the uncertainty in the values to be assumed 

 for the equivalent conductance of the separate ions.J The conclusion pre- 

 viously drawn by one of us from Tower's transference data that sulphuric 

 acid at 18 up to 0.2 normal does not contain an important quantity of 

 hydrosulphate-ion is therefore not justified in consideration of the effect 

 of the possible errors. 



Further light is thrown on the ionization relations of sulphuric acid 

 through a consideration of those of potassium hydrogen sulphate. Con- 

 clusions in regard to the hydrogen-ion concentration in solutions of this 

 salt may be drawn from its molal conductance (A), provided we make 

 certain approximate assumptions. For, designating by y 1 , y 2 , and y 3 the 



*Z. phys. Chem., 27, 52 (1898). fj. Am. Chem. Soc, 26, 10 (1904). 



JThus at 18 assuming Ah = 315, Aso 4 = 68, and Ahso 4 = 35, the two transference 

 numbers for the cathion are 0.822 and 0.800, while, if as concluded by Noyes & Kato 

 (see section 116, Part XI) Ah = 335 (for a 0.05 normal solution), the two transference 

 numbers become 0.831 and 0.811. Tower found 0.823 and Bein 0.813 at 18. The 

 value of Ahso 4 is also very uncertain. 



A. A. Noyes, Z. phys. Chem., 53, 251 (1905). 



