HERMANN VON HELMHOLTZ 



basis of Carnot's principle, and was first given in a 

 somewhat less definite form by Clausius, who pub- 

 lished his work soon after he had reported to the 

 Physical Society of Berlin on Helmholtz's paper on 

 the Conservation of Energy. Helmholtz, in 1883, 

 also applied the principle to chemical phenomena. 1 

 Starting from the fact that heat never passes from 

 a colder to a warmer body without making the 

 former colder and the latter warmer, and that all 

 the energy which already exists as heat cannot be 

 converted into visible external energy, he drew a 

 great distinction between free and restricted energy. 

 Thus the energy of the chemical changes in a galvanic 

 element cannot, without further chemical changes, 

 become a measure of the electro-motive force ; only 

 a small part of the energy appearing as electrical 

 energy. In all chemical changes in which heat 

 appears, all the energy does not appear as heat, but 

 a portion is still locked up in the chemical compounds. 

 Thus the internal energy of a system may be said to be 

 composed of free and restricted energy, of which the 

 former can be changed into work while the second 

 appears as heat. He thus gives us a glimpse into the 

 dynamics of chemical processes, and especially those of 

 dissociation. 



2. On Hydrodynamics. 

 Helmholtz published eight important papers on the 



1 WitfenschaftL Abhandlungen, Bd. iii., s. 92. 

 194 



