356 KEPOET— 1886. 



for sp. gr. 1-25. M. Bouty finds that the ratio X attains a minimum for a concen- 

 tration about 1/500, as the following table shows : — 

 Initial concentration . i i ^ -Lj ^i- _i_ ^^ _i_ -i-^ 

 A 1-917 1-894 1-867 1-856 1-849 1-854 1-881 1-942 2-002 



' One does not see how to explain a variation of this kind except by a change 

 in the nature of the electrolyte {i.e., of the dissolved hydrate).' 



By making the hypothesis, which Bourgoin made, that the hydrate really 

 decomposed by the current was S„Og, 6H,p, M. Bouty considers that the anomaly 

 of electrolysis as expressed by Hittorf s values of «, and also that of conduc- 

 tivity, is explained. These are Hittorf 's values of n for dilute sulphuric acid. 



'S = -5574 1-4383 5-415 23358 97-16 161-4 



n =-400 -288 -174 -177 -212 -206 



Hydrochloric acid is in much the same condition as sulphuric acid : it conducts as 

 if its molecule contained three equivalents of basic hydrogen. One does not know 

 such a hydrate, but there is probably a mixture of hydrates present. 



Oxalic and picric acids are the best conducting organic acids. Other acids con- 

 d-uct hardly at all when strong, and dilution has an enormous effect upon them — 

 probably because they combine with water forming compounds analogous to salts. 



IX. Injluence of Temperature. — To study this, the U tubes of fig. 1 are turned 

 upside do svn and immersed in a bath. The result is that for normal neutral salts 

 the conductivity is a linear function of temperature. 



where h is the same constant for all the salts, and equal to about -0.337. This 

 agrees with Kohlrausch also. 



It is noteworthy that Poiseuille gives the quantity of water which flows 

 through a capillary tube, under a given pressure, as proportional to — 



1 + -03365!! + -00021 i!^ 



It is impossible not to be struck with the identity of the principal coefficient 

 in this formula, with h in the conductivity formula ; showing that resistance is of 

 the nature of a friction, as Wiedemann surmised. 



For abnormal salts the coefficient 6 is a little greater, and a parabolic formula is 

 required at higher temperatures. So, although these salts conduct worse than 

 normal ones to begin with, they improve faster when heated, and accordingly their 

 abnormality decreases with rise of temperature. 



For acids and bases the temperature-coefficient is rather less, being only -0119 

 for sulphuric acid, and -024 for liydrochloric. Probably warming breaks up some 

 good-conducting hydrate, and so spoils conductivity almost as fast as it otherwise 

 improves it. 



' To sum up : I believe I have established that the electrolysis of neutral salts 

 is a simple phenomenon, and that there is only one elementary law of conductivity 

 in harmony with the law of electro-chemical equivalents. Apparent exceptions 

 only reveal to us the complexity of certain solutions which are not directly com- 

 parable vpith those of KCl or K^SO^.' 



On ihe Employment of Alternating Currents for Measuring Liquid 

 Resistances. By MM. Bouty and Foussereau.^ 



The authors criticise the employment of alternating currents employed by Kohl- 

 rausch and many others in the hope of diminishing the effect of polarisation. They 

 point out that self-induction in the resistance-box is fatal to silence in the telephone 

 [naturally], and only succeed in getting good results when they replace wire in their 

 bridge by liquid resistances, describing for this purpose a liquid rheostat. Even 

 thus, however, they hardly get concordant results when they try to apply the method 

 to extremely weak solutions. 



' S means weight of water combined with one gramme of acid. 

 2 Jouriml de Phyiiqve, 2e ser. September 1885, t. iv. 



