268 Prof. Clausius on the Difference between 



monize with this fact in reference to the volume. According to 

 these observations, it must be considered as established that the 

 isolated atoms of which ozone consists do not remain isolated 

 and form molecules for themselves, but in some manner or other 

 fix themselves on to the molecules of the surrounding ordinary 

 oxygen, and form with them complicated molecules. But in 

 order to retain the essential part of my explanation, definite as- 

 sumptions must be made as to the constitution of the complicated 

 molecule thus formed. 



It must first be assumed that the complicated molecules do 

 not consist of several pairs of atoms, as if several ordinary oxygen- 

 molecules were united together, but that the atoms which form 

 active oxygen are contained as unpaired atoms in the mole- 

 cules. The simplest case of the kind is that when each of the 

 complicated molecules consists of a pair of atoms, and an active 

 atom joined to it; but if there are several active atoms in it, 

 these must be in such positions that they form among themselves 

 no pairs, but adhere to the molecules as atoms, and as such can 

 be separated from it. In order further to explain the strong 

 oxidizing action of active oxygen, it must be assumed that it is 

 easier to separate those unpaired atoms from the molecules than 

 to separate from one another two atoms forming a pair — that, 

 compared with the force with which two paired atoms mutually 

 adhere, the unpaired atoms are only loosely united. 



According to this, the second change which I consider I must 

 make in my explanation consists simply, instead of assuming that 

 the atoms are completely free, in saying that they may possibly 

 be either free or loosely united. 



The case in which an atom is loosely united to any molecule 

 is chemically very little different from that in which it is free ; 

 and it was the more obvious to consider it also in my first expla- 

 nation, since I even then compared the active oxygen contained 

 in pure oxygen with that which occurs loosely united in the 

 peroxides or oxides of the noble metals. I must therefore con- 

 fess a want of care on my part in laying any weight upon the 

 point that the atoms are quite free, and for this reason, holding 

 the result of the first observations of Andrews and Tait im- 

 probable, and that I did not from the first designate both cases 

 as equally possible. Assuming the alternative, that the unpaired 

 atoms may either be free or loosely united, the explanation in- 

 cludes not only the active oxygen contained in pure oxygen, and 

 that which in any chemical compound is contained in such a 

 manner that it readily passes into other compounds, and thus 

 can so far be called active, but it also includes oxygen in statu 

 nascent e. 



I will make some observations as to how, on my view, the com- 



