Intelligence and Miscellaneous Articles. 235 



which these bodies experience in the electrical or in the magnetic 

 field. 



Experiments which Quincke * made with liquids in the electrical 

 field, have shown that substances which have almost the same 

 dielectric constant have a totally different behaviour as regards 

 change of volume f. This seems to favour the supposition that at 

 any rate in this case Tc' is an independent constant characteristic 

 of individual substances. Hence for these substances Poisson's(l) 

 or Betti's (2) formula, which appears to connect Jc' with Jc in a 

 perfectly definite manner defined by formulas (3) and (4), seems to 

 be in disaccord with experiment ; fcr these substances Jc must be 

 regarded simply as an empirical constant. 



It follows further from these considerations that the application 

 by many authors of Poisson's formula to the determination of the 

 fraction g of the volume actually occupied by the molecules is only 

 allowable in the case of gases, but for other substances is wanting 

 in accuracy. — Wied. Anncden, vol. xliv. p. 173. 



ON THE ELECTROMOTIVE FORCE OF GAS BATTERIES. 

 BY GERTSCHO MARKOVSKY. 



The results of these experiments may be stated in the following 

 terms : — 



1. The electromotive force of a platinum plate coated Avith 

 hydrogen against a platinum plate in sulphuric acid freed from 

 gas, has not the value which has been previously assumed. For 

 hydrogen the force is smaller, that is =0*646 volt and for oxygen 

 greater =0*374 volt. 



2. Hydrogen and oxygen gases developed electrolytically act 

 just in the same way as when formed by purely chemical action. 



3. By the addition of solution of platinum sulphate the electro- 

 motive force of an oxygen element is diminished, while that of a 

 hydrogen one increases, and in such a manner that the electro- 

 motive force of an oxygen-hydrogen element is not changed by the 

 addition of solution of platinum sulphate. 



4. The electromotive force is independent of the change of 

 density and temperature of the gas introduced. 



5. Carbon electrodes behave in a gas element, or when polarized 

 by a current, differently from platinum electrodes. — Wiedemann'.* 

 Annalen, vol. xi., 1891. 



* Wied. Ann. vol. x. p. 523, 1880. 

 t Thus for oil of turpentine, where 



for petroleum, where 

 for rape oil, where 

 and therefore a decrease 



K = 2 ' 412 ' o^ 17 



K=2*124, Av =19*23; 



' v . 10° 



K=2*442, — = - 18*24 . 10-6 

 v 



