TRANSACTIONS OF SECTION B. 657 



various salts in dilute aqueous solutions. The pressure of water vapour from 

 salt solutions seems to support the relation 



MR, Aq - M'E,Aq = MR',Aq - M'Il',Aq 5 

 and if this be so, then 



M,R - M',R = ]\I,R' - M',R', 



a relation which is shown to be in accordance with the probabilities of the case. 



G. Oil a ^rohahle Manifestation of Chemical Attraction as a Mechanical 

 Stress. By Professor John W. Langlet. 



Attention was first called by Gladstone and Tribe, in ' Proc. Roj'. Soc' six. 

 p. 498, to the fact that a piece of copper in a solution of argentic nitrate 

 caused the formation of a dense solution of copper nitrate containing more of the 

 radicle NO3 than the average solution. The present writer endeavouis to explain 

 the cause of this concentration. Experiments are given showmg that a concentra- 

 tion of the acid radicle occurs when a salt is formed from an acid in solution, 

 whether a metal, a metallic oxide, or a metallic hydrate be employed, and the 

 degree of concentration for several cases is given. 



Experiments with electrolysis are then detailed, using the so-called non- 

 polarisable electrodes, and by suspending one electrode from the beam of a balance 

 it is found that the establishment of electrolysis consists of two stages — a variable 

 and a permanent one. During the first there is a (/ain in weight at the positive, 

 and a loss at the negative electrode, which is exactly opposite to the permanent 

 action of the cell. This action is shown to depend on the nature of the acid 

 radicle employed, being greatest with bromine and least with acetic acid. 



The action dining the variable stage is then shown to be only apparently iu 

 contravention to the accepted laws of electrolysis, but, on the other hand, does 

 denote something which is an addition to those laws. It is proved experimentally 

 that there is an actual accumulation of acid radicle around one pole, and a 

 diminution at the other for a Pleasurable distance, and involving weighable 

 quantities. The hypothesis is then offered that these phenomena are due to a 

 linear attraction acting selectively between the metal and the acid radicle, and is 

 common to the formation of a salt from an acid in solution by any process, 

 electrical or otherwise. 



Under the hypothesis, and from experimental measurements, it is shown that 

 for a value of chemism expressed in electrical measure as a difference of potential 

 of "5 + volt and a quantity equal to '69 coulomb per square centimetre, the value 

 of the chemism of copper for SO^ equals terrestrial gravitation at -00124 milli- 

 metre distance. 



7. Notes on some peculiar Voltaic Combinations. By C. R. Alder Weight, 

 D.Sc, F.B.S., and C. Thompson, F.C.S. 



I. Gas-film Electeo-moioes. 



The combinations referred to under this title constitute a class of cells in which 

 tlie essential featm-e is that one or both of the ' plates' of the combination consists 

 of a film or aura of gas attracted physically to, or condensed upon, the surface of 

 an electrically conducting solid not appreciably acted upon chemically during the 

 production of a current, but simply serving as a support for the gas-film, which 

 does undergo chemical change. Grove's well-known oxygen-hydrogen 'gas battery,' 

 and the various analogous combinations examined subsequently by others, are ceils 

 of this kind, where both plates are gas-films. We have recently examined a 

 number of combinations intermediate in character between these and ordinary one- 

 fluid or two-fluid cells, one plate only being a gas-film. 



Single gas-Jilm electro-motors, as these may be conveniently termed, may be 

 ranged in two classes, according as the solid plate supporting the gas-film acquires 

 the higher or lower potential. When air, oxygen, or other electro-negative gas 



1887. u u 



