254 Prof. Clausius on the Difference between 



atoms, by which the oxide is reduced and at the same time the 

 active oxygen is transformed into ordinary oxygen. 



With reference to this double action of oxidation and deoxi- 

 dation, I compared active oxygen as it may be contained in 

 ordinary oxygen, with that oxygen which is loosely united in 

 certain peroxides, or in the oxides of the noble metals; and 

 taking peroxide of hydrogen as an example, I said*, "Peroxide 

 of hydrogen, for instance, has a strong oxidizing action, for it 

 readily gives up its second oxygen-atom. If, on the contrary, 

 peroxide of hydrogen is brought in contact with the oxides of 

 the noble metals, or with certain metallic peroxides, a mutual 

 reduction takes place. Here it may be assumed that the oxygen- 

 atoms which separate from peroxide of hydrogen unite to form 

 molecules with those which are liberated from the metallic oxides 

 or peroxides." 



I then proposed the question, Why cannot the readily separable 

 oxygen-atoms contained in an individual oxide or peroxide unite 

 with .each other as readily as the oxygen- atoms of one compound 

 unite with the oxygen-atoms of another ? Among the reasons 

 which I considered possible for answering this question occurs 

 this, that the oxygen-atoms of different compounds may be in 

 different electrical conditions, and the electrical difference may 

 make the atoms of one compound more suitable for uniting 

 with the atoms of another compound than among themselves. 



On the mutual reduction of two peroxides, Brodie, in a beau- 

 tiful paper published in the Philosophical Transactions for 1850, 

 which was unknown to me at the time I wrote my paper, has 

 expressed an opinion which in one point resembles my own, but 

 in others is essentially different. Brodie assumes that the oxygen 

 of the two compounds which act on one another are in different 

 chemical conditions. He says, oxygen is " chemically polar ,; in 

 the compounds, and he distinguishes the positive polar and the 

 negative polar condition. Two quantities of oxygen in these 

 two conditions seek to unite chemically just as oxvgen and hy- 

 drogen can unite. The question, upon what does the chemical 

 difference of both quantities of oxygen depend ? and as to how the 

 molecules are constituted, he does not decide, but at the end of 

 his paper states that this question is an open one. He seems, 

 however, inclined to the view that the substances which in 

 chemistry are considered simple, may even be composed of other 

 elements, " that they consist of yet other and further elements." 

 Of oxygen he says specially, " On this view the real fact which lay 

 hid under these phenomena might be the synthesis of the oxygen 

 from the ultimate and further elements of which the oxygen con- 

 sisted." 



* Phil. Mag. S. -1. vol. xvi. p. 50. 



