318 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



formation of supersaturated solutions. Reactions between silver per- 

 chlorate and 'hydrochloric acid, mercuric chloride and trimethyltin 

 chloride take place instantaneously in benzene. 51 Small amounts of 

 water greatly influence the conductance of solutions of this type. 



While these results are in good agreement with the ionic hypothesis, 

 it cannot be said that reactions cannot take place between the un- 

 ionized molecules. For example, methyl iodide precipitates silver iodide 

 in solutions of silver perchlorate in benzene. If reactions of this type 

 are ionic, we must modify, somewhat, our notions relative to the nature 

 of organic compounds. Yet not a few facts are in excellent agreement 

 with such a view. 



Reactions of the electrolytic type, in which one metal is substituted 

 by another more electropositive metal, have also been studied in sol- 

 vents of low dielectric constants. 52 Such reactions often take place 

 readily. It appears not unlikely that they are in fact electrolytic. The 

 properties of solutions of substances of the electrolytic type in solvents 

 of low dielectric constant have received all too little attention. The 

 data so far are too fragmentary to warrant drawing conclusions of a 

 general nature, but it is not to be doubted that the study of such systems 

 will lead to important results. Electrolytic phenomena are not confined 

 to solvents of high dielectric constant. Evidence is constantly accumu- 

 lating which supports the view that all fluid media possess, in some 

 degree, the power of forming electrolytic solutions under suitable con- 

 ditions. 



9. Factors Influencing lonization. a. The Ionizing Power of Sol- 

 vents in Relation to Their Constitution. Since, as we have seen, the 

 ionizing power of a solvent is largely determined by its dielectric con- 

 stant, it follows that, in seeking to determine possible relations between 

 the constitution of a substance and its ionizing power, we should seek 

 for relations between the dielectric constant and the constitution of the 

 substance in question. Water, hydrocyanic acid and formamide have 

 the highest dielectric constants of substances so far investigated. 



The nature of the relation between the dielectric constant and the 

 constitution of liquid media is not clear. There is, however, an obvious 

 relation between the dielectric constant of the hydrogen derivatives of 

 the elements and their position in the periodic system. The hydrogen 

 derivatives of the first members of the various groups invariably exhibit 

 a dielectric constant much greater than that of the following members. 

 Similarly, the dielectric constant of the hydrogen derivatives of elements 



61 Observations by Messrs. Callis and Greer in the Author's Laboratory. 

 "Gates, loc. cit. 



