4 Cain, The Constitution of the Ammonium Compounds. 



manner for the whole of the facts referred to above, and 

 the formulae for ammonium chloride and ammonium 

 hydrate would be 



H3N = CIH, H3N = 0H,, 



in which chlorine is triad and oxygen tetrad. The 

 statement that, in the case of a pehtavalent nitrogen 

 atom, only four valencies can attach themselves to an 

 organic radical, the fifth being always united to a halogen 

 or hydroxyl group (cp. Vaubel, Stereochemische For- 

 schungen^ 1899; Wedekind, Zur Stereocheinie des fUnf 

 wertigen Sticksioffes, 1899) is at once explained in the 

 light of this formula. It is perhaps hardly necessary to 

 adduce evidence in favour of the conception of triad 

 chlorine. Thus Armstrong writes {Encycl. Brit. loc. cit): 

 " As it is clear that iodine may exercise triadic functions, 

 " the remaining halogens can scarcely be denied the rank 

 "of potential triads"; and, again, Ramsay says {Modern 

 Chemistry) : " It must ... be assumed that the halogen 

 " atoms are . . . possibly triads." " The mode of com- 

 " bination of these double salts {i.e., ZnCl2. 2KCI) is 

 " possibly owing to the fact that the halogens are capable 

 " of acting as triads." That oxygen can often become 

 tetravalent is to-day generally accepted.^ 



The union of ammonia and hydrochloric acid is very 

 simply explained by the equation 



H3N + ClH-^HgN = CIH: 

 The influence of moisture on this combination is, in my 

 opinion, the same as in the case of the union of carbon 

 monoxide and oxygen where there is no question of 



* Although, as I find, these formulje occur, together with corresponding 

 ones for tetramethylammonium iodide and tetraethylphosphonium iodide in 

 a paper by Heyes on Valency (Phil. Mag., 1888 [5], 25, 297), yet no 

 arguments are used in favour of them, and no further application of them is 

 made. 



