S Cain, The Constitution of the Ammonium Compounds. 



and one which, of course, has no parallel in the very 

 simple configuration of the carbon atom. In this way- 

 has been developed the cubic formula of van't Hoff, the 

 double tetrahedron of Willgerodt and the square pyramid 

 of Bischofif. If we, however, accept the formula which is 

 here presented, no new assumption has to be made in 

 order to arrive at a space configuration. The nucleus 

 N = CI, instead of a carbon atom, is supposed to be at the 

 centre of a tetrahedron, and we have 



I I 



— N = CI — corresponding to — C — 



The number of possible isomers is shown by the 

 following table : — 



General 

 formula. 



Number 



of 

 isomers. 



Formulae of isomers. 



NAAAACl 

 NAAABCl 

 NAABBCl 

 NAABCCl 

 NABCDCl 



I 

 2 

 2 



3 



4 



A3N = C1A. 

 A3N = C1B.A,BN = CIA.0 

 A,BN = C1B.AB,N = C1A. 

 ABCN = CIA . A,BN = CIC . A^CN = CIB. 

 BCDN == CIA . ACDN = CIB . ABDN = CIC . ABCN = CID.O 



The corresponding formulae for acids other than 

 hydrochloric are easily written. 



The formula for tetramethylammonium iodide, viz., 

 (CHJ3N = ICH3 



(^) These would be the formulse of Kipping's hydrindamine salts {/<jr. cit.) 

 (^) Three of these have been prepared in the case of the Phenyl methyl 



allyl benzyl ammonium iodides ; two optically active (Pope and Peachey, 



toe. cit, ) and one inactive ( Wedekind, loc. cit. ). 



