202 Proceedings of Royal Society of Edinlurgh. [sess. 
ing at 106°, and later another melting at 158-159°. They are both 
found to possess the composition of a monophenyl-hydrazone of 
benzoin, and to be identical in molecular weight. These facts, 
with the similarity in mode of preparation, point to identity in 
chemical constitution. 
The lower- melting isomer may be made alone by heating the 
constituents together without intervention of alcohol. 
2. Both substances form small white needles. The differences 
between them are differences in degree only. The melting-points 
are 52-53° apart. The lower-melting isomer here, as in previously 
described cases, is much more soluble in ordinary solvents than the 
other, and is much less stable in its general relations. Following, 
therefore, the established precedent, it has been designated the 
/5-hydrazone, to distinguish it from the more stable, or a-hydrazone. 
The relative instability of the p variety is shown by the fact that 
it is rendered oily by heating in alcohol for some hours, and is soon 
so far decomposed that no crystals can be obtained from the solution. 
The a variety is unaffected by this treatment. 
3. The identity in chemical constitution was proved by the 
conversion of both into the already known diphenyl-hydrazone of 
benzil, CgHg - C(N 2 HC 6 H,) - C(X 2 HC 6 H 5 ) - C^H^, by the action of 
excess of phenyl-hydrazine in acetic acid solution, and by other 
reactions. 
4. Finally, as in the case of other isomeric hydrazones, the 
P modification was transformed into the a modification. This was 
accomplished by heating it in alcoholic solution with two molecules 
of phenyl-hydrazine. When we consider the instability of the 
jS-hydrazone, the yield of *5 gram of the pure a-phenyl-hydrazone 
from 1 gram of the isomer indicated an unexpectedly complete 
transformation. 
This case of stereo-isomerism is specially interesting, as in no 
previous case could both modifications of the hydrazone be obtained 
directly. One of the isomers was always obtainable only from the 
ketone=chloride, or by transformation from the other. 
