1 78 Dr. C. R. A. Wright on the Determination of 

 whence 

 •sB^Kl-nOHj-niAx + Cl-^Bi-fi^-SGH)}^, 

 \vliicli may for shortness be written 



e =E 1 +[2{(l-»)H}-S(nA)-S(H)] x X 



62. According to the particular values which the several 

 terms in this expression may have, various values for e may 

 be deduced. On examination it is found that all the apparently 

 abnormal variations in the value of the counter E.M.F. set up 

 during electrolysis, of the subsequent polarization, and of the 

 closely allied E.M.F. produced by gas-batteries and analogous 

 combinations may be satisfactorily accounted for by this 

 expression *. Thus, for instance, suppose water to be elec- 

 trolysed with platinum poles, so that no chemical action takes 

 place between the electrodes and the products, whilst no 

 suppression of hydrogen by the action of dissolved oxygen, 

 or of hydrogen by dissolved oxygen takes place ; then 

 X(H) = 0. If now the electrode be supposed to be destitute 

 of adherent or occluded gases to commence with, and the 

 current be very minute, the whole of the water decomposed 

 will be transformed into hydrogen and oxygen in a highly 

 condensed form, whence, since n { = l and n 2 =l, 



e=E 1 -(/ il +/* 2 ) x J=E 1 -2(%J. 



Under such conditions therefore the water will be electrolysed 

 by an E.M.F. less than 1'50 volt (the value of Ej), Experi- 

 ment shows in fact that when well-boiled water (either nearly 

 pure or acidulated with sulphuric acid) is decomposed with 

 recently ignited platinum electrodes, an E.M.F. scarcely ap- 

 preciably greater than will suffice to enable a current to 

 pass, whence (li x -f 7* 2 )% J must, under these conditions, nearly 

 = 1-50 volt, 



or Aj + A 2 must nearly =34,100 gramme-degrees ; 



that is, the heats of condensation of oxygen and hydrogen by 

 platinum Sfc. jointly may amount to almost as large a quantity 

 as that developed by their union to form liquid ivater. 



That the work done in the condensation of a film of gas by 

 attraction to or occlusion in a solid body is great relatively to 

 the mass of gas condensed is well known. The Author, con- 



* At the request of the Publication Committee of the Physical Society, 

 the discussion of several particular cases of this theorem and of their 

 bearing upon and explanation of various phenomena observed by previous 

 experimenters is omitted. 



