484 Mr. W. Coldridge on the Electrical and 



Another group might be (SnOl 4 ) 10 ; another (SnCl 4 ) 12 ; &c. 

 Then to call stannic chloride homogeneous, if thus composed 

 of aggregates of varying complexity, is to use the term in an 

 approximate and statistical sense, or subject to a reservation 

 that it applies only to the ultimate molecules and not to the 

 aggregates they form. The main purpose of this conception 

 is the vivid realization of a condition of elephantine stability, 

 one that shall afford a foundation for the dissociation processes 

 which are associated with electrolytic conductivity. Thus, 

 when Armstrong discusses the effect of water on the conduc- 

 tivity of the halogen acids, he submits the view that the 

 dilution improves the conductivity by decomposing the more 

 complex molecules ; and generally he concludes, when the 

 molecular conductivity is low, then there are big molecular 

 aggregates. The liquid stannic chloride would consist of 

 massive groups. This conception is fruitful, and explains 

 many phenomena. But a simpler explanation may serve 

 these purposes as effectively. It thus becomes of interest to 

 consider whether it is necessary to adopt this view of the com- 

 plex aggregates in the place of the simple molecular compo- 

 sition, whether stannic chloride is composed 



( a ) ! SnCl 4 j | SnCl 4 j j SnCl 4 | 



or 



(£) jTnCJTj | SnOI 4 j j SnCl 4 j 



In consideration of this question, it may be advanced that 

 stannic chloride in the gaseous condition does consist in 

 molecules represented as in (a). 



But it may be urged that some gases which have at high 

 temperatures simple constitutions have at lower temperatures 

 more complex ones. Thus nitrogen peroxide is " N0 2 " at 

 high, and gradually passes into a !&<£)" at low temperatures. 

 Mallet has observed that hydrofluoric acid is " H 2 F 2 " just 

 above its boiling-point. The density of acetic-acid vapour 

 corresponds to a molecule C 3 H 6 3 within a few degrees of its 

 boiling-point, and then, as the temperature rises, rapidly dimi- 

 nishes to a density which gives the molecular weight of 60. 



Do, then, these observations lead by induction to the result 



that, as the vapour of | SnCl 4 | is condensed into a liquid, the 



molecules coming nearer and nearer coalesce into complex 

 aggregates ? If this induction be correct, then the liquid 

 must have the constitution ft. 



