1886.] Conduction and Molecular Composition, &c. 21 '3 



acids : it appears to me that many — indeed all — of his observations afford 

 most distinct evidence in favour of the view I have expressed above. 

 The general result of his investigation is that the molecular conduc- 

 tivity increases with dilution : in other words, that the dissolved sub- 

 stance exercises a greater specific effect, finally attaining a maximum ; 

 it then diminishes, but he believes this to be due to impurities in the 

 water, especially to neutralisation of the acid by traces of ammonium 

 carbonate. The maximum, he appears to think, would be the same 

 for all acids if the dilution could only be pushed far enough : in the 

 case of monobasic acids it is about 90 (arbitrary units) ; it is twice 

 this in the case of dibasic, thrice in the case of tribasic, and so on. 



I will quote first his results in the case of solutions of hydrogen 

 chloride, bromide, iodide, fluoride and silicon fluoride. 



Table T. 



V. 



HC1. 



HBr. 



HI. 



HF. 



H,SiF 6 . 



2 



77-9 



80-4 



80-4 





47-81 



4 



80-9 



83-4 



83-2 



6-54 



57-29 



8 



83-6 



85-1 



84-9 



7-59 



62-20 



16 



85-4 



86-6 



86-4 



10 00 



67-08 



32 



87-0 



87-9 



87-6 



13 14 



71-52 



64 



88-1 



88-9 



88-7 



17 38 



75-61 



128 



88-7 



89-4 



89 '4 



23 11 



79-22 



256 



89-2 



89-6 



89'7 



30'30 



83-39 



512 



89-6 



89-7 



89 7 



39 -11 



91-62 



1024 



89-5 



89-5 



89 -3 



49-49 



109 -5 



2048 



89-5 



88 -9 



89 



59 56 



144-0 



4096 



88-6 



87-6 



87-8 



69-42 



187-1 



8192 











226-6 



16384 











258-6 



32768 











282-6 



Tt will be observed that hydrogen chloride, bromide and iodide 

 practically behave alike ; the numbers for the chloride are, however, 

 slightly lower than those for the bromide and iodide, and the maxi- 

 mum is not reached quite so soon in the case of the chloride. Hydro- 

 gen fluoride is altogether different : its molecular conductivity is 

 exceedingly low to begin with, and is considerably below the maxi- 

 mum even when ^ = 4096. But I would call special attention to the 

 numbers for hydrogen silicon fluoride, which is commonly regarded as 

 a dibasic acid : at first, as Ostwald says, it behaves as a monobasic 

 acid of moderate strength — iodic acid, for example ; but the maxi- 

 mum for monobasic acids being exceeded, the molecular conductivity 

 increases more and more rapidly, ultimately exceeding the treble 

 value, 270. It must be supposed that it undergoes decomposition in 

 accordance with the equation — 



H 2 SiF 6 + 2H 2 = SiO, + GHF. 



