Mr Townsend, The formation of clouds with ozone. 57 



Hence the pressure of the acid is ^ . : .. 0Q , assuming that each 



molecule of the acid exerts a pressure equal to a gaseous molecule. 

 In this case, since each molecule of acid ionizes into two hydrogen 

 atoms and one S0. 4 group, the pressure exerted by the sulphuric 

 acid would be three times the above amount. 



Thus we get : 



2T_6&> 10" 

 ~a~98 ' 9 * 



Taking T=74 we get: 



co = = -4 x 10~ 2 , when a = 5 x 10 -5 . 



a 



Hence the ratio of the weight of acid in the drop to the weight 

 of water is *4 x 10 -2 , so that when the water is removed from the 

 drop its volume is reduced to 2 x 10 -2 of its original size (sp. gr. of 

 H 2 S0 4 = 2, q.p.) and will consist of a drop of acid of radius 6'2 x 10 -6 . 



6. The cloud which is formed when ozone is bubbled through 

 turpentine differs in some points from those which are described 

 above. It can be shown by the method described in section 3 

 that the cloud is due to the action of ozone on turpentine vapour. 

 The clouds which are formed by the potassium iodide and sodium 

 metabisulphite solutions can be removed by bubbling the gas 

 through sulphuric acid, but immediately the gas comes into con- 

 tact with water the cloud reappears. In the case of the cloud 

 formed with turpentine, its density is not diminished to any 

 marked extent by bubbling through sulphuric acid ; so that we 

 see that the main constituent of the drops is turpentine and the 

 ozone dissolved in them prevents them from evaporating. 



7. We therefore conclude from the above experiments that 

 gases evolved from the liquids through which ozone has been 

 passed play the most important part in the formation of the cloud, 

 and that although hydrogen peroxide may be made by the action 

 of ozone on water vapour, its presence is not necessary to explain 

 the phenomena. It is moreover difficult to explain the phenomena 

 on the hydrogen peroxide theory, since there is no cloud formed 

 when ozone comes into the presence of water vapour, which on 

 this hypothesis would mean that hydrogen peroxide is not formed. 

 And since the cloud is formed when iodine, sulphur dioxide or 

 turpentine are in the atmosphere we should have to suppose that 

 the presence of these gases facilitates the formation of hydrogen 

 peroxide. Although, arguing from analogy, such a reaction might 

 take place, still there is not sufficient evidence in support of this 



