57 MOLECULAR AND ATOMIC ENERGY 131 



calculated values of e as we were able to deduce the speed of 

 translatory motion of the molecules from the molecular 

 energy E. It would rather be allowable to estimate the 

 strength of chemical affinity from the atomic energy e. 



But from what has been said regarding the character of 

 the atomic energy we further draw this as a necessary con- 

 clusion, that an atom cannot, like a molecule, attain any 

 speed we choose. A great speed exceeding a certain limit 

 would be able to tear the atom from its combination with 

 the others, and such a freed atom would then move on in 

 straight lines free from external forces like an independent 

 molecule, and its energy, therefore, which till then formed 

 a part of the atomic energy, would go to increase the mole- 

 cular energy E. Herein lies an evident ground for the view 

 that the mean energy e of an atom must be smaller than 

 the average energy E of translatory motion of the mole- 

 cules. 



That an atom can be actually loosened from the mole- 

 cular combination by an increase in its speed cannot be 

 doubted ; to this testifies the fact of dissociation, that is, the 

 phenomenon that chemical combinations can be broken up 

 by a rise of temperature, and, therefore, by an increase in the 

 energy of the molecules and of the atoms. With a moderate 

 amount of heat this breaking up of molecules into single 

 atoms does not in general occur ; but among a great number 

 of molecules there will always be some which become split 

 up into their components in consequence either of extra- 

 ordinary high speed or of collision under exceptionally 

 favourable circumstances. 



This view, first put forward_by Clausius, is applicable 

 not only to gases but also to liquids. From measurements 

 on the conductivity of water made by F,._Kojy^aTisc h and 

 A. Heydweiller 1 it may with great probability be assumed 

 that evenTEe" purest water contains traces of uncombined 

 oxygen and hydrogen. 



Analogously to this partially occurring dissociation we 

 should expect a partial chemical combination to result when 

 two gases are mixed together at a temperature bel^w that 



1 Sitzungsber. d. Berl Akad. 1894, p. 295. ? 



K 2 



