Proceedings. 91 



October last, and referred to the Russian chemist's mathe- 

 matical method for determining the presence of definite 

 compounds. 



Dr. HODGKINSON made a communication on phenomena 

 associated with diamond cuts on glass. 



Professor H. B. DixON made a communication " On 

 the Union of Hydrogen and Nitrogen." He said: — 



In 1877, when I was demonstrator in Dr. Lee's labora- 

 tory at Christ Church, Oxford, I assisted Mr. A. Vernon 

 Harcourt in an experiment in which we endeavoured to 

 bring about the combination of nitrogen and hydrogen by 

 the silent discharge. Contrary to the statement of Mr. W. F. 

 Donkin {Proc. Roy. Soc. xxi. 281) we found no trace of 

 ammonia formed. Mr. S. Johnson has more recently 

 expressed the opinion that nitrogen exists in two allotropic 

 modifications, the first of which more easily unites with 

 hydrogen than the second ; and that the action of heat on 

 the first variety is to turn it into the second. According 

 to this view, the nitrogen prepared by passing air and 

 ammonia over heated copper and copper oxide (Mr. 

 Harcourt's method) would consist wholly of the second or 

 inactive variety, and would not unite with hydrogen to 

 form ammonia. The existence, however, of these two 

 varieties of nitrogen has not, I believe, been confirmed by 

 other chemists. Mr. Harcourt has recently informed me 

 that, finding the decomposition of ammonia to be appre- 

 ciably incomplete when induction sparks are passed through 

 the dry gas over mercury, he was led to the conclusion that 

 the same sparks must bring about the union of hydrogen 

 and nitrogen to an appreciable extent. This conclusion he 

 has verified by experiment. 



I have repeated this experiment in a eudiometer with 

 platinum-iridium electrodes 2 mm. apart. 30 cc. of a 

 mixture of dry hydrogen and nitrogen* were collected over 



* The nitrogen was prepared from air by passing it over red hot copper. 



