Chemical Properties of Stannic Chloride. 481 



question a review will now be made : — of the chemical cha- 

 racteristics, as far as they are pertinent, of those compounds ; 

 of the possible influence of their physical aggregation ; and, 

 lastly, of the conditions under which the power of electroly- 

 sability can be developed. 



To take the liquids seriatim : — 



Water is characterized by its stability and by its large heat 

 of formation. If it could be directly oxidized to hydrogen 

 peroxide, the change would involve a large absorption of 

 energy, 



(H 2 0, 0) = 23,100 cal. 



Thus it is not possible for pure water to become nonhomo- 

 geneous through the formation of any peroxide : the only 

 other way in which water could become chemically nonhomo- 

 geneous, save through the formation of molecular aggregates 

 of varying complexity, would be by its dissociation in part 

 into hydrogen and oxygen atoms ; but this is a most remote 

 speculative chance and a practical impossibility. 



Hydrofluoric Acid is the only compound of hydrogen and 

 fluorine. There is neither a perfluoride (HF Z ) nor a sub- 

 fluoride (HJF). Moissan examined the product of the elec- 

 trolysation of liquid hydrofluoric acid, rendered a conductor 

 by the presence of dissolved potassium hydrogen fluoride, and 

 found no evidence of such a change as 



H.F^H + H^F,, 



and established that the ions, as liberated, are simply hydrogen 

 and fluorine. 



Hydrochloric Acid is the only compound of hydrogen and 

 chlorine. I think that no one has endeavoured to perform 

 with liquid hydrochloric acid experiments analogous to those 

 of Moissan's for the sake of their electrolytic importance. 



Staimic Chloride in the vaporized condition can exist per- 



fectly as a collection of like unit particles, molecules | SnCl 4 | 



There is a lower compound, stannous chloride ; but the forward 



change, — ,„ ^ _. 



& ' SnCl 2 + Cl 2 -^-SnCl 4 , 



occurs with the utmost readiness. A strong presumption 

 therefore exists against the possibility of the reverse dissocia- 

 tion, except at high temperatures ; and there is no evidence 

 in support of such an hypothesis. 



Thus, then, water, hydrofluoric acid, hydrochloric acid, 

 stannic chloride, agree in their chemical homogeneity. 



Whilst there is the closest resemblance between tha above 



