PROFESSOR IN BERLIN 339 



the Thermodynamics of Chemical Processes : Conclusions 

 relating to Galvanic Polarization/ he applies the thermo- 

 dynamic theorems previously developed to the theory of 

 galvanic polarization, ascribing great importance to them in this 

 connexion, ' because they show that the surplus of the free 

 energy of the mixture of oxygen and hydrogen over that of the 

 water depends largely upon pressure, while the development 

 of heat in the compound is almost independent of it. So long 

 as it was believed that the electromotive force of polarization 

 must be calculated according to the latter (as I did myself in 

 my earlier work) it appeared to be an almost unalterable 

 quantity, and this made certain processes in the polarization of 

 a voltameter almost inexplicable. But if the electromotive 

 force is calculated according to the free energy, it is then found 

 to be exceedingly liable to alteration according to the gaseous 

 saturation of the layers of liquid lying next the electrodes, and 

 this essentially modifies the interpretation of a large proportion 

 of the phenomena of polarization, so that most of those which 

 were previously inexplicable can now be understood/ 



Helmholtz had showed in his earlier work of 1873, that the 

 gases dissolved in the liquid, oxygen in particular, have a great 

 influence on the intensity of the current, for the unlimited 

 duration of which, with weak E.M.F., no explanation had been 

 found, and had then explained the origin of the convection 

 currents dependent upon them ; experiments undertaken with 

 the view of removing the last trace of dissolved gases were 

 unsuccessful. The opposing force of polarization, too, increased 

 steadily with the increased E.M.F. of the galvanic battery, 

 where there had been a prolonged evolution of gas. Helm- 

 holtz now believed that he had solved these difficulties by his 

 thermodynamic theory, since it was plain from this that the 

 resistance of the chemical forces to the electrical current 

 increases steadily with the solution in the liquid of the gases 

 given off at the electrodes. Finally he also applied his theory 

 to the formation of gas bubbles after the saturation of the 

 layers next the electrodes with gas, and calculated the work 

 corresponding to the diffusion of the gases through the liquid. 



He ascribed great importance to thermodynamic researches 

 in the scientific development of chemistry, saying in an interest- 

 ing letter in 1891 : 



Z 2 



