ON THE STEREOCHEMISTRY OF NITROGEN. 181 
Professor Kipping observed a particularly interesting kind of isomerism 
among compounds of this type in which 6 and X both contain an asym- 
metric carbon atom.' This isomerism has now been very fully investigated 
in an admirable way by himself and his collaborators.” 
Externally compensated (d. /) a-hydrindamine when treated with 
d-brom-camphorsulphonic acid, with the corresponding chlor acid, 
or with cis x camphanic acid, was found to give rise to unequal quantities 
of two salts called the a and # salts, the 3 salt being that which is formed 
in smaller quantity. These salts differ in crystalline form, in amount of 
water of crystallisation, and often also in specific rotatory power ; these 
differences are not removed by recrystallisation from hot water, and both 
salts contain the inactive base. 
It is unnecessary to discuss the large mass of detailed work which has 
been done in the painstaking demonstration that only one explanation of 
this isomerism is possible : * a brief summary of the conclusions will suffice. 
It has been clearly shown that each of the two active hydrindamines, 
on combining with one of the above-mentioned acids, gives rise to two 
salts called ad and Sd and al and /3/ respectively, and that the original a 
salt obtained from the d-/ base is a mixture of ad and al in the form of a 
partially racemic compound, whereas the original 3 salt consists of a 
mixture of the two /3 salts or even of all four salts; in this case it is 
called a partially diracemic compound. 
In some cases there is a striking similarity between the ad and /3d or 
the a/ and {3 salts respectively, which may be isodimorphous and not 
completely separable by crystallisation. The molecular rotatory powers 
of the /3 series of salts in aqueous solution are frequently abnormal, which 
may be due to incomplete electrolytic dissociation or to activity of the 
nitrogen atom (see page 190). 
Evidence of a similar kind as to the existence of isomerides has 
been obtained for the brom-camphorsulphonates of benzylhydrindamine,! 
methylhydrindamine,* and /-menthylamine,® and for the chlor-camphor- 
sulphonate of d and/ methylhydrindamines,’ although in these cases it 
seems impracticable to isolate the salts free from their isomerides. 
The mandelates, tartrates, camphor-7 sulphonates, and camphor-a 
sulphonates (Reychler) of these bases do not exhibit the same phenomena : 
these salts appear to be homogeneous. This isomerism, though extremely 
important from a theoretical point of view, appears not to be of general 
occurrence. 
1 Trans. Chem. Soc., 1900, 77, 861. 
2 Trans. Chem. Soc., 1903, 83, 873, 889, 902. 
% Trans. Chem. Soc., 1903, 88, 937, 1147. 
+ Trams. Chem. Soc., 1901, 79, 430. 5 1903, 83, 918. 
6 1904, 85, 65. 7 Tattersall, 1904, 85, 169 
