Validity, and Residual Affinity. 309 



Hotter. 



Colder. 



IC1 



IC1 3 



SnCl 2 



Sn 2 Cl 4 



GaCl 3 



Ga 2 Cl 6 



H 2 



H 2 2 



C 2 H 4 2 



4 H 8 4 



C 2 H 4 



C 6 H 12 3 



If these speculations are well founded, we ought to be able 

 to predict the discovery of " allotropic forms " of nitrogen and 

 the halogens. The allotropy of six of the non-metals already 

 seems certain; most of the others are open to suspicion: 

 chemists are naturally cautious and conservative on these 

 fundamentals of doctrine. A dirty element may easily be 

 called a new element or another " allotropic form." Never- 

 theless there are signs of surprises in store for us — dim vistas 

 though they be. In the case of known compounds, also, 

 there may be two metameric prussic acids, viz. 



C=N— H and H— G=N. 



Calling these the alpha and beta "acids," there is some 

 reason for thinking that it is the alpha acid which is formed 

 during Fownes' reaction for CO from K 4 Fe(CN) 6 , and that 

 probably there is hydrolysis of this HCN, thus : — 



C=N— H 



C 



=o/ H 8 



NIL 



(1) Before. (2) After. 



or 



(1) Before, H— N=C= = + ^=OH 2 , 



(2) After, H— N=H 2 + C=0. 



But if so, there ought surely to be some means of distinguishing 



H 

 the nitrile cyanide, | , from the imide, C=NH, where 



C=N 

 the hydrogen is not directly associated with the carbon, though 

 the problem is evidently more delicate than the discrimination 

 of the two bodies formulated C 2 H 5 CNO, or the two striking 

 and odourless C 3 H 5 CKS liquids now known. 



The distinction to which it is here endeavoured to draw 

 attention, between the mere raising the valency of one 



Phil. May. S. 5. Vol. 25. No. 155. April 1888. " Y 



