OXYGEN AND OZONE. 59 



nitric oxide, and nitric peroxide, according to the propor- 

 tion of oxygen in them, as you will learn in the next chap- 

 ter. A peroxide, is an oxide having the highest amount of 

 oxygen, or at least a higher amount than the nitric oxide 

 in the series named. In the case of the compounds of ox- 

 ygen with the metals, sometimes an oxide is discovered 

 containing less oxygen than the monoxide, and this is call- 

 ed a suboxide, the prefix sub being the Latin for under. 

 Some metals form compounds having one and a half times 

 as much oxygen as the monoxide ; or, what is the same 

 thing, since we can have no half atoms, these compounds 

 contain two atoms of metal to three of oxygen ; they are 

 then called sesquioxides, the prefix sesgui being the Latin 

 for one and a half. Iron gives us an example of this, form- 

 ing Fc 2 O 3 , which you see is a sesquioxide. 



63. Ozone. This is oxygen gas in a peculiar condi- 

 tion, distinguished from common oxygen by its pungent 

 smell and its very active chemical properties. You may 

 perceive the peculiar smell when an electrical machine is 

 in action, owing to the partial conversion of the oxygen 

 of the air into ozone. The easiest way of effecting this 

 change is by means of phosphorus. Place a clean stick of 

 phosphorus in a corked flask having a little water in the 

 bottom, and let the flask stand half an hour. Remove the 

 phosphorus with a pair of pincers, and notice the peculiar 

 odor of the gas in the flask. The phosphorus very slowly 

 oxidizes and induces the formation of a little ozone. Pure 

 ozone has never been made it is always mixed with much 

 oxygen. Ozone when breathed irritates the lungs, and 

 corrodes organic matter. It immediately oxidizes metals 

 which ordinarily unite with oxygen at high temperatures 

 only. 



64. Experiment. Boil as much starch as will cover the 

 point of a penknife with about fifty cubic centimeters of 



