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Prof. H. E. Armstrong. Electrolytic [Mar. 25, 



easily applicable to such cases as these. It also does not appear to 

 afford any explanation of the abrupt change in conductivity which 

 occurs in solid silver iodide and sulphide as the temperature is raised 

 (see p. 280) ; nor of the peculiar variation in conductivity on diluting 

 sulphuric acid with water (see p. 282). 



Again, I venture to think that the conductivity of a mixture of 

 compounds which themselves have little or no conducting power is 

 accounted for in but an unsatisfactory and insufficient manner by the 

 hypothesis put forward by F. Kohlrausch ("Pogg. Ann.," 1876, 159, 

 p. 233) ; there appears to he far too great a difference in the behaviour of 

 the pure compounds, water and liquid hydrogen chloride, for example, 

 and of a mixture — no decomposition apparently of either compound 

 being effected by any electromotive force short of that which produces 

 disruptive discharge, although the mixture of the two will not with- 

 stand an electromotive force of little more than a volt. Influenced 

 by these considerations, I am led to conclude that there is no satis- 

 factory evidence that the constituents of the electrolyte are either 

 free prior to the action of the electromotive force, or are primarily 

 set free by the effect produced by the electromotive force upon either 

 member separately of the composite electrolyte ; but that an additional 

 influence comes into play, viz., that of the one member of the com- 

 posite electrolyte upon the other while both are under the influence 

 of the electromotive force. This influence, I imagine, is exerted by 

 the negative radicle of the one member of the composite electrolyte 

 upon the negative radicle of the other member. Assuming, for 

 example, that in a solution of hydrogen chloride in water the oxygen 

 atom of the water molecule is straining at the chlorine atom of the 

 hydrogen chloride molecule, if when subjected to the influence of an 

 electromotive force the molecules are caused to flow past each other 

 — the phenomena of electric endosmose may be held to afford evidence 

 that in composite electrolytes the molecules are thus set in motion 

 — it is conceivable that this influence, superadded to that of the elec- 

 tromotive force upon the electrolyte, may bring about the disruption 

 of the molecule and conduction : in short, that a state may be induced 

 such as Clausius considers is the state prior to the action of the elec- 

 tromotive force. 



A large amount of most valuable information on the connexion of 

 dilution and electrical conduction in aqueous solutions has been 

 recently published by Arrhenius, Bouty, F. Kohlrausch and Ostwald. 

 In his most recent paper, Ostwald (" Journal fur praktische Chemie," 

 1885, 32, p. 300) has given the results of his determinations of the 

 molecular conductivity m* in the case of no less than about 120 different 



* m — Tcv, k being the specific conductivity as ordinarily defined, and v the volume 

 of the solution, i.e., the number of litres containing the formula weight in grams of 

 the acid. His results are expressed in arbitrary units. 



