OZONE. 349 



component elements, oxygen and hydrogen, we may look 

 on these gases as exhibiting water to us in another form. 

 And a hundred instances of the sort might be adduced, in 

 which, either by separating the elements of a compound, or 

 by re-arranging them, we obtain new forms of matter with- 

 out any real change of substance. But with an element, 

 the case, one would suppose, should be different. 



However, the physicist must take facts as he finds them ; 

 and amongst the most thoroughly recognized chemical facts 

 we have this one, that elementary substances may assume 

 different forms. Chemists call the phenomenon allotropy. 

 A well-known instance of allotropy is seen in red phos- 

 phorus. Phosphorus is one of the chemical elements ; and, 

 as every one knows, the form in which it is usually obtained 

 is that of a soft, yellow, semi-transparent solid, somewhat 

 resembling bees' wax in consistence, poisonous, and readily 

 taking fire. Red phosphorus is the same element, yet differs 

 wholly in its properties. It is a powder, it does not readily 

 take fire, and it is not poisonous. 



Ozone, then, is another form of oxygen. It is the only 

 instance yet discovered of gaseous allotropy. 



And now we have to deal with the difficult and still- 

 vexed questions of the way in which the change from oxygen 

 is brought about, and the actual distinction between the 

 two forms of the same gas. Schonbein held that common 

 oxygen is produced by the combination of two special forms 

 of oxygen the positive and the negative, or, as he called 

 them, ozone and antozone. He showed that, in certain 

 conditions of the air, the atmospheric oxygen exhibits quali- 

 ties which are the direct reverse of those which ozone 

 exhibits, and are distinct from those of ordinary oxygen. 

 In oxygen thus negatived or antozonized, animals cannot 

 live any more than they can in nitrogen. The products of 

 decomposition are not only not destroyed as by ozone, but 

 seem subject to preservative influences, and speedily become 

 singularly offensive ; dead animal matter rapidly putrefies, 

 and wounds show a tendency to mortification. 



