398 SCIENCE PROGRESS 



indicate polymerisation whilst the solutions are fairly good 

 conductors, have already been dealt with (p. 393). 



A matter of great interest is Kahlenberg's experimental 

 proof 1 that instantaneous chemical reactions are possible in 

 solvents which have no appreciable conducting power. He has 

 shown, for example, that perfectly dry hydrochloric acid gas 

 causes an immediate precipitate of cupric chloride when passed 

 into a solution of cupric oleate in dry benzene. On this point 

 it may be observed that, while it is no essential part of the 

 electrolytic dissociation theory that all chemical reactions are 

 ionic, yet this view is undoubtedly held by some of its sup- 

 porters, more particularly by those belonging to the school of 

 Arrhenius. He himself says 2 : "We may assume that in the 

 case of reactions which take place very slowly ions are present, 

 though not in measurable quantity so far as our present methods 

 are able to detect them"; and Euler 3 has attempted, though 

 without conspicuous success, to prove the validity of this 

 assumption. There is, on the other hand, a certain amount of 

 evidence, besides that adduced by Kahlenberg, 4 to show that 

 reactions can take place between undissociated molecules. 

 Thus Shenstone 5 has found that perfectly dry chlorine acts on 

 mercury ; Donnan, 6 and also Slator, 7 are of opinion that 

 the activity of the halogen alkyls cannot be ascribed to the 

 presence of ions, and I have recently obtained results which 

 seem to show that in the splitting up of monochloracetic acid 

 by hot water according to the equation — 



CH 8 ClCOOH + HX> = CH 2 OHCOOH + HC1— 

 it is the undissociated acid molecule which is acted on. For 

 these reasons it seems preferable to assume for the present that, 

 although the ions show exceptional chemical activity, reactions 

 between undissociated molecules also take place in certain cases. 



With Kahlenberg's general conclusion, 8 that " whether a 

 solution will conduct electrically or not depends on the specific 

 character of both solvent and solute," it does not seem probable 



1 Journ. physical Chem. 1902, 6, 1. 



2 Electro-chemistry, English edition, p. 180. 



3 Zeit.physikal. Chem. 1901, 36, 405, 641 ; 1902, 40, 498 ; 1904, 47, 353- 

 * Loc. cit. 



5 Journ. Chem. Soc. 1897,71, 471. 



6 Ibid. 1904, 85, 555. 



7 Ibid. 1904, 85, 1286. 



8 Journ. physical Chem. 1906, 10. 



