TRANSACTIONS OF SECTION B. 521 
ethylene bromide seldom reacts with tertiary bases in the normal manner, Iso- 
kairolin itself with ethylene bromide gives almost exclusively the salt : — 
CH, 
CH, 
Br 
“___0H,.CH,.Br 
CH, CH, 
It has not yet been found possible to bring the Br in the —CH,Br group into 
reaction with a second molecule of isokairolin. 
I do not consider that our present knowledge is sufficient for successful 
theoretical speculation on the configuration and isomerism relations of the 
pentavalent nitrogen atom. This, however, is certain, viz.: in active ammonium 
salts the tetra-atomic radical N.a. b.c. d.,the centre of activity, must possess 
tetrahedric grouping. This radical occurs in solution as the free active cation. 
The fifth valency, which is not always satisfied, cannot—apart from other grounds— 
possess equal value. I picture it in a rectilinear lengthening of a tetraheder axis, 
as the following sketch shows :— 
This configuration is that proposed long ago by van't Hoff, and since then 
revived by Aschan. The latter has also deduced the inactive isomers (prepared 
by Le Bel, Kipping, Aschan, and Wedekind) from this scheme. In my opinion, 
the change of places of the different radicals, or, still more, the lack of change of 
places of the different radicals (appearance of isomerism), is so little understand- 
able that even with the help of this model we cannot as yet form any clear ideas 
of the intramolecular reactions among the ammonium salts. I incline more and 
more to the opinion that, in the case of nitrogen which shows such different 
behaviour, one must discard the idea of a fixed valency. The theories which 
Werner has developed for carbon may be useful here. They allow, too, of an 
explanation of autoracemisation without the assumption of dissociation. Let us 
consider affinity as a force acting uniformly from the nitrogen atom, considered 
as a sphere, towards the surface. Then we can imagine the five radicals fixed as 
five ‘ valency positions’ on the surface of the sphere. Four of these could take 
up a tetrahedral grouping, if in this position the greatest exchange of affinity took 
place. Now, the intra-molecular movements of the radicals in substituted 
ammonium salts are particularly evident. This is proved by the tendency towards 
change of place. These movements appear, then, as pendulum-like oscillations about 
the valency position, and are increased by rise of temperature, by the action of 
sunlight, and by other unknown causes, until, finally, a change of place occurs, just 
as Werner assumes in the case of compounds containing asymmetric carbon. 
(Explanation of autoracemisation of brom-succinic acid.) 
I do not consider it, however, impossible that the five radicals would cause a 
different grouping of the valency positions, when the force acting between them is 
of a different nature. Such groupings are perhaps the pyramid formula, or the 
double tetrahedron of Willgerodt. The latter might occur when two negative 
radicals are combined with a tertiary amine. The attractions and repulsions 
