1904] . The Decomposition of Ammonia ly Heat. 117 



temperatures varied from 677 to 1111. It was found that the reaction 

 is essentially monomolecular, being similar to that for arseniuretted 

 hydrogen, as found by van't Hoff. The rate of decomposition is much 

 quickened by the presence of traces of some of the metals, those tried 

 being mercury, iron, and platinum. 



We are indebted to the Government Grant Fund of the Royal Society 

 for the cost of most of the apparatus employed, and wish to express 

 our great obligations to Principal Griffiths for the loan of some of his 

 apparatus for platinum thermometry, and for his kind guidance in its 

 use. 



Supplementary Note, May 27, 1904. We have assumed that the 

 decomposition of ammonia is an irreversible reaction, i.e., k' = in the 

 general formula dx/dt = Jc (a-x) (b-x) . . . - k' (a' + x) (b' + x) . . . 

 for Ramsay and Young showed* that on passing a mixture of dry 

 nitrogen and hydrogen through a heated glass tube containing iron 

 filings, or through a red-hot iron tube, no appreciable quantity of 

 ammonia was formed, a result which we confirmed by experiments of 

 our own some years back, obtaining the same result also with a glass 

 tube containing porcelain. We find, however, that this view of the 

 matter is not generally accepted; Ostwald, for instance, in his 

 ' Grundlinien der anorganischen Chemie 'f states that, on heating 

 ammonia, equilibrium ensues when 98 per cent, of the ammonia is 

 decomposed. We should like to point out that the results of our 

 experiments, now described, show no indication whatever of any such 

 equilibrium, for the curves all run towards the origin within the limits 

 of experimental error, whereas, if there were any equilibrium before 

 the ammonia was all decomposed, they would cut the horizontal axis 

 to the left of the origin, and, moreover, the equilibrium would change 

 with the temperature. 



We have mentioned that a trace of ammonia was always found in 

 the globe at the end of an experiment, but this probably came from 

 the cold stem ; and, moreover, since the rate of decomposition may be 

 taken as proportional to the amount of ammonia present, that amount 

 can, strictly speaking, never quite reach the zero point. 



Whether a minute quantity of ammonia remains finally undecomposed 

 would not be indicated by these results, and we intend to approach the 

 subject from another direction, and to examine generally the conditions 

 under which nitrogen and hydrogen combine to form ammonia. 



* Loc. dt, 

 t 1900, p. 345. 



