112 Mr Jones, Some substituted ammonium compounds 



the angular points of a tetragonal pyramid about a point inside 

 it (Fig. 1), and Willgerodt's ' double tetrahedral ' configuration, 



which represents three of the groups as lying in the same plane 

 with the nitrogen atom while the other two are placed along a 

 line at right angles to it on opposite sides (Fig. 2). 



On either of these configurations a substance of the type 

 NR'R"Rz"X should exist in isomeric forms. Taking the first 

 configuration and using a plane projection for simplicity, the 

 possible isomers would be represented as follows : 



Fig. 3. 



Fig. 4. 



The first compound is planisymmetric and should therefore 

 exist in one form only, the other compound having no plane of 

 symmetry would consequently be expected to exist in two forms, 

 non-superposable mirror images of one another and optically 

 active (Figs. 5 and 6). 



The present investigation is an attempt to detect this charac- 

 teristic isomerism, which may be compared to that observed in 

 compounds with two asymmetric carbon atoms, such as the tartaric 

 acids. This note describes some of the compounds which have 

 been prepared in the course of the work. 



