Nae a) pone Le ee 
72 | REPORT OF SCHIMMEL & Co. OCTOBER 1914/APRIL 1915. 
whether it is pure. 
As stated in our above Report, we obtained quite unsatisfactory results 
testing made-up mixtures according to this method. The mixtures having been adapted 
in their composition to eucalyptus and cajuput oils, the unfavourable results were 
directly applicable to the oils themselves. C. T. Bennett*) has come to a similar 
opinion of this method. 
Dodge’) has now published an answer to these criticisms, in which he advocates 
once more the suitability of his method. He reproaches us as well as Bennett with 
not having sufficiently observed his indications, reducing on the one hand the quantity 
of oil to half and, on the other, not examining the cineol separated off as to its 
purity. Such an examination, however, was absolutely necessary in order to establish 
the completeness of the oxidation and to avoid too high results. A loss of cineol 
was possible by oxidation of part of it, but the reaction could be so conducted that 
this question was of no practical importance. Dodge himself thinks his method 
inadequate for oils of a cineol content of less than 50 p.c., but does not consider 
this of any consequence, as such oils do not generally come into consideration for 
pharmaceutical purposes. Endeavours to simplify the method in one direction or the 
other have failed, but it was found that, except at the beginning of the oxidation, 
strong cooling is required. Only when the reaction slackens down, it may be conti- 
nued at ordinary temperature. 
The reply as rendered above cannot alter in the slightest degree our opinion as 
to the unsuitableness of Dodge’s test. If one followed his suggestion to experiment 
with each oil until in every isolated case the correct conditions for testing have been — 
found out, it would mean such a loss of time and material as no one can ordi- 
narily afford. 
Physical Notes. 
See page 81 as to synthesis under the influence of light. 
Concerning modification of density and of index of refraction of essential oils 
according to the temperature, see page 68 of this Report. 
Absorption curve of some ketones. 
In a treatise by G. G. Henderson, J. A. R. Henderson and J. M. Heilbron*) on the 
selective absorption of ketones, we find a description of the curves of absorption of 
fenchone, camphor, menthone, cyclohexanone, m-, o-, and p-methylcyclohexanone, 
carvone, methylheptenone, in addition to other numerous ketones of no interest for 
our special domain. Some of the ketones used in these experiments were purified 
by being converted into their semicarbazones, others by means of the disulphite 
compounds or by repeated distillation. 
Occurrence of natural camphor in different forms. 
It has been found that natural camphor possesses the quality of crystallizing in 
different forms. F. Wallerant*) observed that, at ordinary temperature, camphor deposits 
1) Perfum. Record 8 (1912), 295; Report April 1918, 63. — *) Journ. Ind. Eng. Chemistry 6 (1914), 863. — 
8) Berl. Berichte 47 (1914), 876. — 4) Compt. rend. 158 (1914), 597. 
