46 SECTIONAL ADDRESSES 
partial rotation of the carbonyl-radical might perhaps become possible 
by assuming with Lowry and Walker that an additional centre of dis- 
symmetry is developed within the chromophoric group in optically active 
aldehydes and ketones. 
From the above considerations it appears that the molecular theory of 
optical rotatory power, as de Mallemann has called it, is not capable in its 
present form of expressing the rotatory power of any but the simplest 
molecules ; and the crudeness of some of the assumptions on which it is 
based, and the importance of the secondary effects which it ignores, 
forbid any expectation of extensive developments in the near future. 
Nevertheless the theory has proved to be of real value in demonstrating 
the simplicity of the conditions which suffice to give rise to optical 
rotatory power, since this effect can be produced by four isotropic spheres 
which are near enough to pass on to one another the alternating polarisa- 
tion produced by an incident beam of light, without requiring any more 
complex form of coupling ; and chemists will always be grateful for a 
theory of optical rotatory power which makes it possible to identify the 
actual configurations of the dextro- and levorotatory forms of the simplest 
organic molecules, in parallel with a similar claim which has recently been 
made by Kuhn in the more complex case of the spiro-compounds (68). 
On the other hand, no theory of optical rotatory power which is limited 
to the region of transparency can be regarded as satisfactory, and further 
progress must depend on an intensive study of rotatory dispersion in the 
region of absorption. For this purpose the optically active aldehydes 
and ketones provide ideal material, since the position and intensity of the 
optically active absorption bands are both well adapted for precise 
experimental work, and two cases are already known in which the partial 
rotation of the chromophoric radical has been automatically isolated. It 
therefore only remains to determine, perhaps by the methods of wave- 
mechanics, the conditions under which the electronic cloud of the carbonyl- 
radical becomes optically active, and the factors which determine the 
magnitude of its partial rotation, in order to provide a complete solution 
for this special case, and thus to pave the way for a general solution of 
the whole problem. 
REFERENCES. 
I. WALKER, ‘ Arrhenius Memorial Lecture,’ J. Chem. Soc., 1928, 1400. 
2. OSTWALD, ‘ Faraday Lecture,’ J., 1904, 85, 508. 
3. SOMMERFELD, Atombau und Spektrallinien. 
4. OLIPHANT, Nature, 1934, 188, 377. 
5. Lowry, J., 1898, 78, 569. 
6. J., 1898, 78, 986. 
7. J., 1899, '75, 211. 
8. DuUBRUNFAUT, C.R., 1846, 28, 38. 
g. WHEELER and TOLLENS, Ann., 1889, 254, 310. 
to. Lowry, J., 1899, 75, 213. 
J., 1898, 78, 991. 
. Lapwortu and KipPinG, J., 1896, 69, 304. 
HOH 
NOH 
