OZONE AND HYDROGEN PEROXIDE D ALTON'S LAW '211 



Hydrogen peroxide, especially in a concentrated form, in contact with 

 these substances, evolves an immense quantity of oxygen, so that an 

 explosion takes place and an exceedingly powerful evolution of heat is 

 observed if hydrogen peroxide in a concentrated form be made to fall 

 in drops upon these substances in dry powder. An exactly similar de- 

 composition takes place in dilute solutions. 27 



Just as a whole series of metallic compounds, and especially the 

 oxides and their hydrates, correspond with water, so also there are 

 many substances analogous to hydrogen peroxide. Thus, for instance, 

 calcium peroxide is related to hydrogen peroxide in exactly the same 

 way as calcium oxide or lime is related to water. In both cases the 

 hydrogen is replaced by a metal namely, by calcium. But it is most 

 important to remark that the nearest approach to the properties of 

 hydrogen peroxide is afforded by a non-metallic element, chlorine ; its 

 action on colouring matters, its capacity for oxidising, and for evolving 

 oxygen from many oxides, is analogous to that exhibited by hydrogen 

 peroxide. Even the very formation of chlorine is closely analogous to the 

 formation of peroxide of hydrogen ; chlorine is obtained from manganese 

 peroxide, MnO 2 , and hydrochloric acid, HC1, and hydrogen peroxide from 

 barium peroxide, BaO 2 , and the same acid. The result in one case is 

 essentially water, chlorine, and manganese chloride ; and in the other 

 case there is produced barium chloride and hydrogen peroxide. Hence 

 water + chlorine corresponds with hydrogen peroxide, and the action 

 of chlorine in the presence of water is analogous to the action of 

 hydrogen peroxide. This analogy between chlorine and hydrogen 

 peroxide is expressed in the conception of an aqueous radicle, which 

 (Chap. III.) has been already mentioned. This aqueous radicle (or 

 hydroxyl) is that which is left from water if it be imagined as deprived 

 of half of its hydrogen. According to this method of expression, caustic 

 soda will be a compound of sodium with the aqueous radicle, because it 

 is formed from water with the evolution of half the hydrogen. This is 

 expressed by the following formulae : water, H 2 O, caustic soda, NaHO, 



27 To explain the phenomenon an hypothesis has been put forward by Brodie, Clausius, 

 and Schonbein which supposes ordinary oxygen to be an electrically neutral substance, 

 composed of, so to speak, two electrically opposite aspects of oxygen positive and negative. 

 It is supposed that hydrogen peroxide contains one kind of such polar oxygen, whilst in 

 the oxides of the above-named metals the oxygen is of opposite polarity. It is supposed 

 that in the oxides of the metals the oxygen is electro-negative, and in hydrogen 

 peroxide electro-positive, and that on the mutual contact of these substances ordinary 

 neutral oxygen is evolved as a consequence of the mutual attraction of the oxygens of 

 opposite polarity. Brodie admits the polarity of oxygen in combination, but not in an 

 uncombined state, whilst Schonbein supposes uncombined oxygen to be polar also, con- 

 sidering ozone as electro-negative oxygen. The supposition of the oxygen of ozone being 

 other than that of hydrogen peroxide is contradicted by the fact that in acting on barium 

 peroxide strong sulphuric acid forms ozone, and dilute acid forms hydrogen peroxide. 



p 2 



