482 Mr. W. Coldridge on the Electrical and 



nonconducting liquid acids and the conducting liquid hydro- 

 cyanic acid, in point of their physical properties, it may yet 

 be possible to distinguish it chemically : at least it is worthy 

 of note that 



(H, C, N)=- 28,400, 



for such a large endothermic formation is suggestive of a 

 tendency towards instability. 



The observations of Bleekrode and De La Rue (Proc. Roy. 

 Soc. xxv. p. 323), showing its power of electrolysing, are 

 worthy of confirmation, provided all possible precautions be 

 taken to ensure the use of an absolutely anhydrous specimen. 



In considering the phenomena presented by the fused salts, 

 it is necessary to recall the warning given by Prof. Armstrong 

 as to the scantiness of accurate data at the command of the 

 inquirer into the properties of fused pure substances. Having 

 noted this warning, a statement made by Faraday is very 

 apposite. In the first volume of his l Experimental Researches 

 in Electricity/ § 690, when he is discussing the results he 

 had obtained with fused antimony trichloride, he suggests 

 that the conductivity he had observed " might be due perhaps 

 to a true protochloride consisting of single proportionals 

 (SbCl)." In a word, Faraday surmised that the fused com- 

 pound was not quite homogeneous. A similar suggestion 

 may be advanced : that silver chloride, silver iodide, selected 

 as two of the best examples of Faraday's law of Liquido- 

 Oonduction, are not homogeneous compounds in the fused 

 state. Photo-salts — whether they be definite compounds or 

 mixtures is of no import — exist and are characterized by the 

 extreme facility of their formation. Probably with more 

 accurate information at command it will be possible to advance, 

 in explanation of the electrolytic conduction of fused sub- 

 stances, this view of the imperfect homogeneity, itself sup- 

 ported by separate and nonelectrical considerations ; and to 

 establish as an expression of a complete uniformity that no 

 homogeneous liquid is an electrolyte : electrolisability involves 

 an antecedent condition of heterogeneity. 



But in such a statement as that no homogeneous liquid is 

 an electrolyte it is necessary to accurately determine the sig- 

 nificance of the word " homogeneous.^ Without hesitation, 

 for example, pure liquid stannic chloride would be spoken of 

 as homogeneous. The statement would be accurate if the 

 whole of the stannic chloride were composed of precisely similar 

 unit molecules. But a view has been expounded in a pro- 

 found paper by Prof. Armstrong, "On Electrolytic Conduction 

 in relation to Molecular Composition; Valency and the Nature 



