Active and Ordinary Oxygen. 265 



My explanation, on the contrary, definitely refers the pheno- 

 mena to a simple molecular constitution ; for it starts by assum- 

 ing that the molecule of ordinary oxygen is diatomic, and that 

 the atoms have the tendency, when they are free, again to com- 

 bine in pairs to form molecules. When there is an electrical 

 opposition between two oxygen-atoms, their union will thereby 

 be promoted ; but even when this opposition does not exist, the 

 tendency to union is still present, and the electrical opposition 

 is then spontaneously produced by their union. 



In this manner it is explained why the oxygen-atoms of a 

 compound unite more readily with the oxygen-atoms of another 

 compound which are in another electrical state, but that, under 

 suitable conditions (for instance, with increased temperature), the 

 oxygen-atoms of an individual compound may leave it and unite 

 to form molecules, and that thereby oxygen is formed of the 

 same kind as when two quantities of oxygen contained in different 

 compounds come together. Brodie's view, according to which 

 only such quantities of oxygen as have opposite chemical pola- 

 rity seek to unite, leaves this last process unexplained; and even 

 also in the other processes there is a greater indefmiteness than 

 in my explanation. 



From what I have said, I can express so much of the expla- 

 nation contained in my former paper as, after recent discoveries, 

 I conceive myself justified in adhering to, in the following two 

 sentences, one of which formed from the first the chief point of 

 my explanation, and the other in the course of the discussion was 

 taken as probably true : — 



1. Ordinary oxygen consists of united, active oxygen of isolated 

 atoms. 



2. The two atoms which form a molecule of ordinary oxygen are 

 in opposite electrical conditions. 



1 proceed now to discuss the points in which I consider I 

 must alter the view which I originally expressed. 



At that time, as already mentioned, it was not known that 

 there was, besides ozone, a second kind of active oxygen ; and 

 with regard to ozone, it was not known that in its relation to 

 the oxygen contained in various compounds there was any 

 such difference as prevails in the deportment of one kind of 

 electricity to the same or to the opposite electricity. Hence I 

 believed that I must consider it as a fact that such a difference 

 does not exist. Now, on the one hand, according to my view of 

 the condition of the ordinary oxygen-molecules, it was presup- 

 posed that the atoms of a molecule at the moment in which they 

 separate are of opposite electricities ; but, on the other, I consi- 

 dered it as a fact established by experiment that the active 

 oxygen resulting from this separation exhibited no properties 



