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, 
Fig. 1. Fig. 2. 
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"R 2 "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, 
