Active and Ordinary Oxygen. 263 



Comparing this explanation with the then known facts, and 

 considering first the most important of the methods for pre- 

 paring ozone, I had occasion to enter upon the condition of the 

 two atoms contained in an ordinary oxygen-molecule, and to 

 express my opinion on the subject. I said that the process 

 which takes place when ozone is produced by placing atmo- 

 spheric air in contact with moist phosphorus, may be conceived 

 to take place in the following manner* : — By the combination 

 of the phosphorus with the surrounding oxygen, a number of 

 the molecules coming in contact with it must be decomposed 

 into their two atoms ; and it may thus happen that it does not 

 unite with both, but that one is removed by the motion of heat 

 from its sphere of operation and then remains isolated. It is 

 possible that another circumstance operates also in this case. It 

 is known from electrolysis that, in the union of dissimilar atoms 

 to form one molecule, one part of the molecule becomes posi- 

 tively, and the other negatively electrical. This perhaps takes 

 place also when two similar atoms unite — for example, two oxygen- 

 atoms — by one of these becoming positive and the other negative. 

 But since, in the oxidation of phosphorus, oxygen certainly enters 

 as negative constituent into the compound, it may be that of 

 the two oxygen-atoms resulting from one molecule, the negative 

 is preferably retained by the phosphorus, and the positive, being 

 unrestrained, or at all events less restrained, can escape. 



In these sentences, and repeatedly throughout the paper, the 

 view has been expressed — as far as I know, for the first time, and 

 at a time when there were no experimental data which neces- 

 sitated it — that the atoms in the ordinary oxygen-molecules are 

 in opposite electrical conditions. By the discovery made shortly 

 after, that there are two kinds of active oxygen, which Schonbein 

 has called ozone and antozone, and that these two can unite to 

 form ordinary oxygen, this view has been remarkably con- 

 firmed. 



With regard to the circumstance that active oxygen can 

 exert an oxidizing and also a deoxidizing action, I gave the fol- 

 lowing explanation. Isolated atoms can form compounds with 

 other bodies more easily than such as are already joined in pairs, 

 and must first be liberated from this union before they are fitted 

 for combination with other bodies ; the former will therefore exert 

 a stronger oxidizing action than the latter. Suppose, further, 

 that an oxide, for example a peroxide, which readily gives up 

 its oxygen or a part of it, is in contact with a gas in which there 

 are oxygen-atoms that have the tendency to combine with second 

 atoms ; these will be able to take from the oxide the feebly united 



* Phil. Mag. S. 4. vol. xvi. p. 47. 



