Mr Townsend, The formation of clouds with ozone. 53 



through a solution of potassium iodide or of sodium metabisul- 

 phite, the antozone is unaffected by the solution and forms a 

 cloud with the water vapour present. When however sodium 

 sulphite is used to remove the ozone no cloud is formed, which is 

 explained by Meissner by assuming that in this case the antozone 

 is also removed by the sodium sulphite solution. This explanation 

 is not generally considered to be correct, but that given by sub- 

 sequent experimenters who advocated the theory that the cloud 

 consisted of hydrogen peroxide is more universally accepted. This 

 latter theory is founded entirely upon the evidence that has been 

 brought forward of the presence of hydrogen peroxide in the 

 cloud, although it is extremely difficult, if not impossible, to 

 detect the presence of hydrogen peroxide in minute quantities in 

 a gas which contains ozone. From the experiments which are 

 here described the following conclusions have been arrived at : 



(a) The cause of the formation of the cloud is due to the 

 action of ozone on a gas which escapes from the solution through 

 which it is bubbled. 



(6) The formation of the drops is in no way due to spray 

 thrown up from the solution. 



(c) The cloud consists mainly of water. 



When a mixture of oxygen and ozone is bubbled through a 

 solution of potassium iodide, iodine is liberated which dissolves in 

 the potassium iodide and gives the solution a red colour ; small 

 quantities of iodine escape from the solution and diffuse through 

 the gas above the solution and into the bubbles of the gas as they 

 rise through the liquid. Similarly with sodium metabisulphide ; 

 sulphur dioxide is formed as the ozone acts on the salt and some 

 of it gets mixed with the ozone. In both these cases a cloud is 

 formed, but when sodium sulphite is used to remove the ozone 

 from the oxygen no gas is formed by the action, and no cloud 

 appears above the solution. The following experiments show that 

 it is to the action of ozone on the gaseous iodine and on sulphur 

 dioxide that the formation of these clouds must be attributed. 



2. The ozone which was used was prepared from oxygen given 

 off by the electrolysis of dilute sulphuric acid. The gas was first 

 passed through a solution of potassium iodide to remove traces of 

 ozone and hydrogen peroxide, and then dried by sulphuric acid. 

 After leaving the sulphuric acid the oxygen was passed through a 

 long tube of calcium chloride and tightly packed glass wool. The 

 oxygen so prepared formed no cloud in the presence of moisture. 

 The end of the tube containing the glass wool was joined to the 

 ozoniser, which is shown in figure I. It was constructed according 

 to Babo's pattern, and consisted of a glass tube, 67 centimetres long, 



