794 lonisatio/i of Gases and Chemical Change. [March 11, 



eiectromerism was increased, there was a rapid increase in chemical 

 action. 



I have recently been able to show that if the union of carbon 

 monoxide and oxygen takes place in a strong- electric field, which has 

 the effect of removing electromers, the chemical action is dimin- 

 ished. Similar experiments are in progress with the mixture of 

 hydrogen and chlorine, combining under the influence of light. 



The next experiment tried, illustrates one way in which the eiectro- 

 merism of a gas may bring about chemical change. Hydrogen sulphide 

 and sulphur dioxide can be mixed at the ordinary temperature in pre- 

 Bence of traces of moisture, but in presence of liquid water, decomposi- 

 tion takes place into sulphur and water. The gases were dried before 

 mixing by calcium chloride, which leaves about 4 mg. of water vapour 

 per litre in the gas. After mixing, a small open silica tube containing 

 about 2 mg. of dried radium bromide was introduced. After six 

 hours no apparent change had taken place in the gas : there was no 

 deposit of sulphur on the sides of the jar, and it seemed at first as if 

 no action had been produced. On opening the jar. however, an 

 inrush' of air was noticed, and the contents were almost odourless. 

 On heating the radium tu])e a large quantity of water was driven off. 

 and a copious sublimate of sulphur was seen. The whole of the 

 gaseous contents of the jar had condensed in the small tube containing 

 the radium bromide. The explanation of this action of radium 

 bromide is probably simple. Water vapour condenses on the elec- 

 tromers emitted, liquid (h'ops are formed, and in them the cliemical 

 action takes place.* 



Prof. Townsend has recently published an account of some experi- 

 ments, in which he has shown that there is a very marked decrease in 

 the mobility of negative electromers in the presence of an amount of 

 water vapour repi'esented by a pressure of y^tb nnn. The air, in his 

 experiments, was subjected to the action of Rontgen rays. 



It is concluded that water in a form approaching to that of a drop, 

 is condensed on the electron even when a very small quantity is 

 present. If this deposition of water molecules on electromers goes 

 on when the amount of water present is still smaller, the theory of 

 Sir J. J. Thomson affords a satisfactory explanation of the influence 

 of moisture on chemical change, since some electromers are always 

 present in ordinary gases. 



[H. B. B.] 



* I have invariably noticed that water collects in tubes containing radium 

 preparations exposed to undried air. The salts are not at all deliquescent, the 

 crystals appearing quite sharp-edged under the microscope. I found that 

 10 mg. of radium bromide exposed to an atmosphere saturated at 0° for two 

 days caused a deposition of water on its surface weighing 1-5 mg. 



