10th February, 1920. 



Professor Gregg Wilson, President of the Society, in the Chair. 



CATALYSIS OE THE SPEEDIN(4-UP OF CHEMICAL 



EEACTIONS. 



By a. Killen Macbeth, M.A., D.Sc, F.I.C., M.R LA. Etc. 



(Abstract.) 



Part I. 



The word catalysis is an unusual one and is doubtless 

 unfamiliar to many, so at the outset a little space may profitably 

 be devoted to an explanation of its meaning and application. It 

 is derived from the Greek and means to unloosen. The term is 

 now reserved for the description of those cases in which the pro- 

 gress of a chemical reaction is accelerated by the addition of a small 

 amount of another substance, which is itself unchanged at the 

 end of the reaction ; this may with some justification be regarded 

 as an unloosening of chemical forces through the agency of the 

 added material. The influencing agent is called a catalyst. A 

 particular case will help to make the matter clear. A mixture 

 of dry hydrogen and oxygen may be kept for a long time without 

 any ap])areut union of the gases (to form water) taking place. 

 The mixture may even be heated considerably without any 

 appreciable combination resulting. If, however, a piece of clean 

 platinum foil is added to the gaseous mixture the reaction 

 immediately commences and sometimes proceeds with such 

 vigour that the platinum becomes red hot and an explosion 

 occurs. This is an example of the catalytic effect of platinum — a 

 normally slow reaction being accelerated by its presence whilst 

 the catalyst itself undergoes no change. 



