392 RECENT PROGRESS IN PHYSICS. 



and form ozone; in like manner phosphorus effects the comhination of 

 the vapor of water with oxygen, hut, as yet, we are not able to tell 

 liow it is done. 



Ozone is decomposed into its components, oxygen and hydrogen, hy 

 heat, as shown by the experiment noticed above. 



De la Eive and Berzelius, indeed, regarded ozone as modified 

 oxygen, and maintained that it could be produced by an electrical jet 

 in dry oxygen, but this is contrary to all Schonbein's analogies. 

 Schonbein presented the following experiment as the most striking 

 proof of the presence of hydrogen in ozone : if air containing ozone 

 be dried as perfectly as possible and then heated, it yields water on 

 cooling to hydroscopic bodies over which it is passed. The ozone is 

 decomposed by heat, and the vapor of water which it contained is set 

 free. 



Ozone is one of the most powerful means of producing oxidation 

 which is known. Air containing ozone being passed for a long time 

 over finely divided metallic silver, the latter is converted into peroxide 

 of silver. The vapor of phosphorus is rapidly oxidized under the in- 

 fluence of ozone, and converted into phosphorous acid .'ind phosphoric 

 acid. 



The fact that the passage of the electrical spark through moist atmo- 

 spheric air forms nitric acid was discovered by Cavendish, in the year 

 1785. Schonbein has proved that under like circumstances ozone also 

 is always formed. 



Since ozone can be produced in moist oxygen by the help of the elec- 

 tric spark, it is evident that the formation of ozone is independent of 

 that of nitric acid. On the contrary, Schonbein has made it appear 

 highly probable that the formation of nitric acid is not a direct effect 

 of electricity, but a secondary effect produced by the oxidizing 

 influence of ozone on the nitrogen of the atmosphere. 



The formation of nitric acid by electricity may be shown in the 

 simplest manner, by exposing, for a time, a paper moistened with a 

 solution of carbonate of potash to a jet of electricity escaping from a 

 wire ; the carbonate, under these circumstances, is converted in part 

 into nitrate of potash. 



The ozone formed by means of phosphorus also produces nitric acid. 

 The mixture of phosphorous and phosphoric acids, which furms in a 

 receiver containing a piece of phosphorus, water, and atmospheric air, 

 is absorbed by water. If this water be colored by a solution of indigo, 

 the color of the latter is immediately destroyed, an effect which neither 

 phosphorous nor phosphoric acid alone can produce. The decoloring 

 is effected by a small quantity of nitric acid, which, formed under the 

 influence of the ozone, is also dissolved in the water. 



That it is actually nitric acid which is here in question is proved by 

 shaking the water with milk of lime ; insoluble salts of lime are 

 formed with the phosphorous and phosphoric acids, while a nitrate of 

 lime remains in solution. 



Davy observed that traces of nitric acid appeared at the positive pole 

 of a pile when a voltaic current passed through water containing air or 

 nitrogen. Here, also, the formation of nitric acid is a secondary effect 



