al ont ee 
SCIENTIFIC AND OTHER NOTES ON ESSENTIAL OILS. 21 
whereas correct results are obtained if petroleum ether is discarded. The same may 
be said of a content of only 50 p.c. of cineol, if besides this only terpene is present. 
But if alcoholic constituents are present at the same time, the method fails either 
completely (No. 3), or the results remain considerably behind the actual values (No. 4). 
Similar observations may be made if cineol is isolated in solid form by means 
of resorcinol, and the compound decomposed. This method of separation is not in 
any way inferior to the arsenic acid process, on the contrary, the latter way yields 
even worse results, if Turner and Holmes’ directions are strictly adhered to by mixing 
the cineol arsenate with petroleum ether. As regards the handiness of the addition 
products with arsenic acid on the one hand, and with resorcinol on the other hand, 
we have made the observation that with mixtures consisting only of cineol and hydro- 
carbons, separation takes place equally well with both methods, but that in the presence 
of alcohols the arsenic acid compound takes decidedly longer to form, consequently 
_ it is more difficult to obtain than the one with resorcinol, and compares unfavourably 
with the latter on account of its sticky consistency. 5 
Thus even under such experimental conditions the resorcinol method is not 
excelled by any other test, and the results become even considerably better if the 
modified method is applied, by shaking the fractions 170 to 190° with a 50 p.c. resor- 
cinol solution’). By this method we have again and again obtained excellent results, 
so that we can strongly recommend this way of determination, for in spite of all the 
statements to the contrary it is very useful and, as far as reliability goes, it is undoubtedly 
far superior to all other methods, including the arsenic acid method. The only draw- 
back is, perhaps, its requiring comparatively much oil, a consideration which. has 
induced us to study the question from a new point of view. As the resorcinol method 
in its original form yields too high values if oxygenous compounds are present, and 
_ as the latter are mainly of an alcoholic nature, it is but natural to assume that 
useful results might be obtained by direct shaking of the oil with resorcinol lye, if 
at the same time the percentage of acetylizable constituents is determined, deducting 
it from the part of the oil dissolved in the resorcinol, after its pereentage has 
been established. The difference should represent the actual cineol content. As will 
be seen from the following table, we have succeeded in obtaining satisfactory values 
in this manner. The calculation of the alcoholic constituents was based on the formula 
CioHisO. As was done in the experiments enumerated in the first table, terpineol was 
chosen as alcohol for the mixtures, this being a natural constituent of cajuput oil. 
In this manner a reliable opinion may be formed as to how the results obtained from 
natural oils are to be valued. Acetylation was carried out in the usual way with 
undiluted oil, as well as in the manner prescribed for terpineol (5 hours’ acetylation, 
the oil being diluted with four times the amount of xylene. Gildemeister, The Volatile 
Oils, 294 ed., vol. I, page 578). The differences throughout were so trifling that, for the 
sake of saving time, acetylation in the usual way may be chosen without having to 
fear that appreciable mistakes may be brought about. It may also be left out of 
consideration that the percentage by shaking is established volumetrically, by acetylation 
gravimetrically. The resulting difference only amounts to fractions of one per cent; a 
correction which might be based on the specific weights is, therefore, not necessary. 
We now come to the results: — 
1) The proposal by Harding, mentioned on page 18, to use hot resorcinol lye for the shaking process is 
quite acceptable, seeing that in this way an easier and quicker separation of the yet undissolved oil parts from 
the lye may be effected. However, there is no reason for an alteration in the concentration of the solution. 
