Radiation of Heat bij Gases and Vapours. 177 



One specimen of nitrogen, obtained from the decomposition 

 of nitrate of potash, produced a deflection of about . . . 1°. 



Hydrogen from zinc and sulphuric acid produced a deflection 

 of about . 1°. 



Hydrogen obtained from the electrolysis of water produced a 

 deflection of about 1°. 



Oxygen obtained from the electrolysis of water, and sent 

 through a series of eight bulbs containing a strong solution of 

 iodide of potassium, produced a deflection of about . . 1°. 



In the last experiment the electrolytic oxygen was freed from 

 its ozone. The iodide of potassium was afterwards suppressed, 

 and the oxygen, plus its ozone, admitted into the tube; the de- 

 flection produced was 4°. 



Hence the small quantity of ozone which accompanied the 

 oxygen in this case trebled the absorption of the oxygen itself*. 



I have repeated this experiment many times, employing 

 different sources of heat. With sources of high temperature 

 the difference between the ozone and the ordinary oxygen comes 

 out very strikingly. By careful decomposition a much larger 

 amount of ozone might be obtained, and a corresponding large 

 effect on radiant heat produced. 



In obtaining the electrolytic oxygen, I made use of two differ- 

 ent vessels. To diminish the resistance of the acidulated water 

 to the passage of the current, I placed in one vessel a pair of 

 very large platinum plates, between which the current from a 

 battery of ten of Grove's cells was transmitted. The oxygen 

 bubbles liberated on so large a surface were extremely minute, 

 and the gas thus generated, on being sent through iodide of po- 

 tassium, scarcely coloured the liquid ; the characteristic odour 

 of ozone was also almost entirely absent. In the second vessel 

 smaller plates were used. The bubbles of oxygen were much 

 larger, and did not come into such intimate contact with either 

 the platinum or the water. The oxygen thus obtained showed 

 the characteristic reactions of ozone ; and with it the above result 

 was obtained. 



The total amount of heat transmitted through the tube in 

 these experiments produced a deflection of .... 71 0, 5. 



Taking as unit of heat the quantity necessary to cause the 

 needle to move from 0° to 1°, the number of units expressed by 

 the above deflection is 308. 



Hence the absorption by the above gases amounted to about 

 0-33 per cent. 



I am unable at the present moment to range with certainty 

 oxygen, hydrogen, nitrogen, and atmospheric air in the order of 



* It will be seen further on that this result is in harmony with the sup- 

 position that ozone, obtained in the manner described, is a compound body. 



