Manchester Mevioirs, Vol. xlviii. (1904), No. 14- 



XIV. The Constitution of the Ammonium Compounds. 



By John Cannell Cain, D.Sc, M.Sc. 



{Communicated by Professor H. B. Dixon, F.R.S.) 



Received March 12th. Read Maixh 2gth, 1^04. 



The theory of ammonium compounds, proposed by 

 Ampere in 18 16 and generally accepted even at the 

 present time has not, in spite of its continuance, been 

 entirely free from attack. 



The objections of Kekule, based on his non-belief in 

 the existence of a pentad nitrogen atom, cannot, of course, 

 be regarded as valid to-day as the doctrine of variable 

 valency is everywhere accepted. 



Thus Japp in the Kekule Memorial Lecture, 1897, 

 says " the doctrine ... of fixed valency ... is, so far as 

 I am aware, without supporters." 



We have long given up, therefore, Kekule's molecular 

 formula of ammonium chloride, 



NH3.HCI, 

 although we still adhere to this method of writing a large 

 number of so-called molecular compounds. 



The difficulty of explaining the union of ammonia 

 and hydrochloric acid in terms of the ammonium theory 

 was raised by Chevreul, and Wurtz (The Atomic Theory, 

 1880) found it hard to explain why the chlorine should 

 give up its affinity for hydrogen, and unite with nitrogen 

 for which it has only a slight attraction. He pointed out 

 that although the separation of chlorine and hydrogen 

 should give rise to a considerable absorption of heat, and 

 the union of chlorine and nitrogen can produce only a 

 feeble evolution of , heat, yet the formation of sal-ammoniac 

 gives rise to a considerable evolution of heat. Wurtz's 



May jth, igo4 



