2 Cain, The Constitution of the Amnioniiitn Compounds. 



explanation of this is that " the affinity of the chlorine for 

 " hydrogen is satisfied by the attraction which it exercises 

 " upon all the atoms of hydrogen within the sphere of 

 " which it is now situated." This, however, goes beyond 

 the confines of the valency theory. The inability of the 

 ammonium theory to explain the extraordinary stability 

 of tetramethyl ammonium iodide to caustic potash has 

 been pointed out by Armstrong in 1888 {Phil. Mag. [5], 

 25, 21), and also in his article "Chemistry" in the 

 Encyclop(2dia Britanmca. He says, " It is highly remark- 

 " able that tetramethyl ammonium iodide should not be in 

 " the least affected by even the strongest caustic alkali, 

 " and that the halogen . . . behaves much as does that 

 " in alkylic haloids. This would seem to be a strong 

 " argument in favour of the view that the halogen is not 

 " simply associated with the nitrogen, but retained in 

 " combination with the hydrocarbon radicle." Armstrong 

 suggested (1888) that this substance should be repre- 

 sented by his " residual affinity " formula 



H3C-^N-I-CH3 

 H3C/ 



An important objection to the ammonium theory has 

 quite recently arisen in the existence of isomeric optically 

 inactive organic ammonium salts. Werner {Annalen, 

 1902, 322, 261) instances the two isomeric trimethyl 

 iso-butyl ammonium salts of Le Bel [Comptes Rendus, 

 no, 144), the two methyl di-ethyl amyl ammonium 

 chlorides of Schryver {Chem. News, 1891, 63, 174), and 

 the ethylene propylene dipiperidinium bromides of 

 Aschan {Ber., 1899, 32, 988). Aschan, however, has 

 contradicted the existence of the latter {Ber., 1903, 36, 

 1 164), and the other two cases may be attributed to 

 dimorphism, (cp. Jones,/. C. S., 1903, 83, 1401). There 



