l'.>10] loiiisation of Gases and Chemical Change. 791 



WEEKLY EVENING MEETING, 

 Friday, March 11, 11) 10. 



Sir William Crookes, LL.D. D.Sc. F.R.S. Honorary 

 Secretary and Vice-President, in the Chair. 



H. Brereton Baker, Esq., M.A. D.Sc. F.R.S. 



lonisation of Cases and Chemical Change. 



The term •"catalytic" was introduced by Berzelius to describe a 

 number of chemical actions which would only take place in the 

 presence of a third substance, which itself was apparently unchanged 

 throughout the reaction. The first cases of such actions were inves- 

 tigated by Sir Humphry Davy in 1817. He showed that many 

 mixtures of gases were caused to unite in the presence of finely 

 divided platinum, at temperatures far beloW' those at which union 

 ordinarily took place. Some years afterwards Faraday investigated 

 similar actions, and attempted to explain them by a supposed con- 

 densation of the gases on the surface of the metal. 



Thirty years ago, Prof. H. B. Dixon investigated the behaviour 

 of carbon monoxide and oxygen when they w^ere dried as completely 

 as possible, and he discovered that under these circumstances electric 

 sparks caused no explosion. Some years before, Wanklyn had dis- 

 covered that purified chlorine did not act on sodium, but he did 

 not identify the impurity, now known to be a trace of water, which 

 causes the vigorous action which takes place under ordinary circum- 

 stances. 



In 1882 Cowper investigated the action of dried chlorine on 

 several metals, and found that the removal of moisture in many 

 cases inhibited the reaction. 



In the following year, working in Prof. Dixon's laboratory at 

 Balliol College, I found that purified carbon could ])e heated to 

 redness in dried oxygeji, and that sulphur and phosphorus could be 

 distilled in the same gas without burning. In the investigations 

 which followed, some thirty simple reactions have been tried by 

 myself and others. It has been shown that hydrogen and chlorine 

 can be exposed to light without explosion, ammonia and hydrogen 

 chloride mixed without union, sulphur trioxide can l)e crystallised 

 on hme, ammonium chloride and mercurous chloride give undis- 

 sociated vapours, hydrogen and oxygen can be exposed to a red heat 

 without explosion, and lastly in 1907 nitrogen trioxide was obtained 

 as an undissociated gas for the first time by carefully drying the liquid, 

 and evaporating into a dried atmosphere. 



