Prof. W. Ostwald's Electrochemical Researches. 107 



is as follows : — Let a vessel contain two parallel electrodes 

 at a distance of 1 centim. apart, and let there be used one 

 equivalent in grams of a specified acid ; then the conduc- 

 tivity of the acid, when diluted with a definite quantity of 

 water, is the equivalent-conductivity for that degree of di- 

 lution. It will afterwards be found more convenient to refer 

 the conductivities of the acids to molecular rather than to 

 equivalent weights. The molecular conductivity of an acid 

 is found in a similar way to that whereby the equivalent- 

 conductivity is determined. The degree of dilution is ex- 

 pressed by the number of litres of solution containing one 

 molecular weight, in grams, of any specified acid. It would 

 be more accurate to express the ratio of acid to water by 

 a molecular ratio, e. g. HC1 : 100 H 2 ; but, as only very 

 dilute solutions are considered here, no essential inaccuracy 

 will be introduced by adopting the more convenient method. 



If the dilution =0 (that is, if no water is present), the con- 

 ductivity of an acid is usually equal to, or is very little greater 

 than, zero. As water is added the molecular conductivity 

 increases, and approaches a maximum which is reached when 

 the dilution is infinite. There is no exception to this general 

 law. The conductivities of the stronger acids, HC1, HBr, HI, 

 HN0 3 , HCIO3, H010 4 , HBr0 3 , HIO3, &c, are nearly at their 

 maxima in moderately dilute solutions ; the molecular con- 

 ductivities of these acids vary but little with the dilution. 



The following table presents the conductivities of some of 

 the stronger acids when the dilution increases in the ratio of 

 the powers of 2. The unit, in terms of which the conduc- 

 tivities are expressed, is 4*248 times greater than the mercury 

 unit. 



V. 



HC1. 



HBr. 



HI. 



HN0 3 . 



H010 3 . 



HC10 4 . 



2 



77-9 



80-4 



80-4 



77-9 



77-9 



791 



4 



80-9 



83-4 



83-2 



80-4 



80-2 



82-2 



8 



83-6 



85-1 



84-9 



82-4 



82-3 



84-6 



16 



85-4 



86-6 



86-4 



84-9 



84-0 



86-2 



32 



87-0 



87-9 



87-6 



863 



85-4 



88-1 



64 



88-1 



88-9 



88-7 



87-4 



86-4 



89-2 



128 



88-7 



89-4 



89-4 



88-2 



87-9 



89-7 



256 



89-2 



89-6 



89-7 



88-4 



88-7 



89-9 



512 



89-6 



89-7 



89-7 



88-8 



88-7 



89-8 



1024 



89-5 



89-5 



89-3 



88-9 



88-6 



89-8 



The molecular conductivities of these acids are nearly the 

 same (Kohlrausch had already observed this for some of these 

 acids) ; they slowly increase and reach a maximum, equal to 



