﻿22 Messrs. E. T. Chapman and M. H. Smith on the 



surrounding it with iced water. A cloth dipped in iced water is 

 now wrapped round the neck of the flask, and the bulb placed 

 in the water-bath for a few minutes until the first signs of reac- 

 tion are visible. It is then removed from the water-bath and 

 wafted about in the air. As soon as the chief part of the reac- 

 tion is over, the flask is replaced in the water-bath for a few 

 minutes. This process is repeated with fresh supplies of mate- 

 rial in clean flasks. The contents of the flasks are now dissolved 

 in water, and the solution so obtained distilled with excess of 

 potash. This solution is very dark in colour. The alkaline 

 distillate, which smells strongly of pyridine, is rendered acid with 

 sulphuric acid, and boiled to expel traces of neutral oily matters. 

 It is then considerably concentrated by evaporation in the water- 

 bath, and finally pieces of potash are added. The oily liquid 

 which rises to the surface is pyridine. It was recognized to be 

 such by its extreme stability, by its odour, and by an analysis of 

 its chloride, the details of which are subjoined. 

 Substance taken, 



•4024. 



Chloride of silver found, '4992 ; 



therefore percentage of CI, 30*69; 



(C 5 H 5 NHC1) requires 3073. 



The above process does not yield the full theoretical quantity 

 of pyridine. Some dark-coloured neutral or slightly alkaline 

 body is produced in large quantity. 



II. Organic Cyanides. 



The question of isomerism amongst the cyanides of the alcohol- 

 radicals, or nitriles, has acquired a great interest since the pub- 

 lication of Hofmann's recent researches on the subject. We must 

 now recognize two distinct kinds of isomerism amongst the ni- 

 triles : — first, isomerism dependent on the linking of the carbon 

 inter se ; second, isomerism dependent on the atomicity of the 

 nitrogen . 



As an example of the first kind of isomerism, we may men- 

 tion cyanide of isopropyle and cyanide of normal propyle or 

 butyro-nitrile. This kind of isomerism can obviously exist in 

 nitriles independently of the atomicity of the nitrogen. 



We may represent cyanogen in three ways : — 



(1) N"' C"" C"" N'". In this case the two equivalents of 

 cyanogen which constitute the molecule are held together by the 

 carbon 



