106 



Eesult of Heating a Mixture of Ammonium Nitrate and 

 Manganese Dioxide. 



Jamks H. Ransom. 



Practically all the work on catalysis, in which the oxides of the metals 

 were the catalytic agents, has been undertaken with those substances which 

 on heating decompose with the evolution of oxygen. It has been thought 

 by some of those who have given the subject careful investigation that, 

 in the case of manganese dioxide, at least, the reaction is one of alternate 

 oxidation and reduction of the catalytic agent. The arguments are not 

 conclusive, however, so that the question whether the manganese dioxide 

 acts as a simple contact agent or takes a chemical part in the reaction 

 remains unanswered. 



It occurred to the writer to try the effect of catalytic agents on sub- 

 stances which, on heating, decompose without the formation of oxygen. 

 It was thought that if the catalytic agent acted simply as a contact agent 

 the temperature of decomposition would be lowered but the products 

 would be the same as when the substance was heated alone; but if the 

 action were chemical the products would be different, perhaps more or 

 less oxidized than when the substance was heated by itself. It was rec- 

 ognized, however, that if the action followed the latter supposition it 

 would not of necessity demonstrate that all so-called cases of catalysis were 

 chemical. Among the substances easily available for such an experiment 

 is ammonium nitrate, which, as is well known, decomposes quite smoothly 

 into nitrous oxide and water. The temperature of decomposition is 20.5°. 



At my suggestion, therefore. Mr. O. C. Haworth, who was then study- 

 ing the effect of various catalji;ie agents, iiiidertook the preliminary in- 

 vestigation of the effect of heating ammonium nitrate in the presence of 

 different oxides, among them being manganese dioxide. He established the 

 facts that the decomposition takes place at a lower temperature than 

 when the nitrate is heated alone: that little if any oxygen or nitrous oxide 

 is {)roduced ; that the gas evolved is niti'ogen. 



