“Notes « ON SCIENTIFIC RESEARCH. 91 
ne ene esieespondingly adulterated oils, but also Hele. leaves. out the other constants, 
which is much. to be regretted, for this would have shown if the refractive index really 
_. is so necessary in testing essential oils, as many people maintain. We have never 
denied that it may be of use in solitary cases. 
~ Utz sums up his judgement as follows, “the finding of the ‘chase power furnishes 
‘us with an additional valuable means for recognising the purity or otherwise of essential 
oils, but it is not feasible however, to judge essential oils merely by reason of having 
_ determined their refractive indices’. We should like to amplify the last remark by 
saying that the. judging of essential oils. solely eee to the refractive index would 
in most cases be quite: impossible. ° 
The “Table of Refractive Exponents” which the optical firm Adan Hilger Ltd., 
London, has got J. N. Goldsmith to compile, may be regarded more as a publication 
_ for advertising purposes. It is discussed further in an English trade-paper’*). We 
satisfy ourselves with the Se 
SSnd 
Besides ethyl alcohol, propyl and butyl alcohol are need: in the prearakon of 
alcoholic. potash for the estimation of: saponification values. Comparative experiments 
‘of A. M. Pardee, R. L. Hasche and Emmet Reid?) on fatty oils, fats and waxes 
shewed that butyl alcohol gives more exact values than ethyl alcohol, especially in 
‘the case of substances which are saponified with difficulty. Since the boiling point 
of butyl alcohol is inthe - neighbourhood of 116.8°, the saponification can be more 
effective on account of the higher temperature. It is to be assumed that butylalco- 
holic potash will also find advantageous employment in the analysis of essential oils, 
in order to saponify quantitatively esters only decomposed with difficulty, e. g., sali- 
cylates, and above all valerianates. Years ago H. F. Slack*) recommended: benzyl 
alcoholic potash for the ester determination of essential oils, but we think butyl alcohol 
is more suitable. In our opinion, the use of butyl- -alcoholic potash must remain con- 
fined to difficultly saponified esters, on purely practical grounds, for the high boiling 
: point of butyl alcohol renders the use of a water bath impossible, which would be 
a great hindrance: to saponification on a large scale, which is the pander of the day in 
es the laboratories of our industrial branches. 
With unsaturated bodies as limonene, pinene, &c., and the essential oils, the iodine 
number is influenced by the quantity of iodine used, and attains a maximum when the 
- quantity of iodine present is from 13 to 17 times the quantity of oil under test. Hence 
by the iodine. value of an essential oil is to be understood the maximum amount 
of iodine combined with 100 g. of the substance. If alcoholic iodine solution is used 
_ instead of the Hubl reagents, the amount of combined iodine is practically independent 
of the temperature between 15 and 45°, and proportional to the excess of iodine used. 
_ The cofstant so determined — the pseudo iodine value of the essential oils—is said 
to form, according to R. Huerre*) the same maximum amount of iodine, which com- 
bines with 100 g. of the substance dissolved in chloroform, to which has been added 
a great excess of alcoholic iodine, and. which mixture has been allowed to stand for 
2 hours at ordinary temperature. 
We are still opposed to the determination ‘of the iodine aadree in essential oils, 
for it can give us no information as to the quality of the oil”). 
+) Eerfum. Record 10 (1919), 198. — 2) Journ. ind. eng. Chem. 12 (1920), 481. — %) Cf. Report 1916, 89. 
— +) Journ, de Pharm. et Chim. VII. 20 (1919), 216. As per Chem. Zentralbl. 1920, Il. 408. — °) Cf. Gildemeister 
and Hoffmann, The Volatile Oils, 2.4 ed., vol. I, p. 569. ' 
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