F J NOTES ON SCIENTIFIC RESEARCH. 69 
benzoate is obtained. The reaction can be beautifully demonstrated by heating the 
almost inodorous benzyl benzoate for a few minutes with alcoholic potash lye, when 
the characteristic odour of ethyl benzoate will become noticeable; odourless benzyl 
salicylate yields with methyl alcoholic potash the distinctly smelling methyl salicylate 
(wintergreen oil). 
In an analogous way ethyl formate and ethyl acetate are formed, when the 
formates and acetates of essential oils are determined. The quantities produced are 
largest if the amount of alkali added is insufficient for the saponification. In the 
presence of a quantity of alkali sufficient for complete saponification, when but very 
small amounts of volatile esters are formed, and by using a water reflux condenser, 
losses owing to volatilization are not to be feared. As safest protection against losses, 
Béhal recommends saponification in a closed vessel at the temperature of the water-bath. 
According to our experience, it is sufficient to use a condensing tube about 
1,5 m. long, in order to avoid losses of volatile esters, so that the intermediate reaction 
is without influence on the accuracy of the usual ester determination. 
Jean Niviére') turns against Béhal’s suggestion to saponify the esters in a closed 
vessel. He first proves by comparative experiments that the classical method of 
saponification’) affords exactly tallying results, if on the one hand a condensing tube 
1 m. long, and on the other hand a water condenser 50 cm. long are used. On the 
other hand saponification in a closed vessel cannot be recommended, as the ester 
numbers of lavender and bergamot oils thus obtained are 3,8 or 1,6, respectively, 
higher than those found under ordinary pressure. 
As formerly stated also by us*), a small absorption of alkali was noticed in 
saponifying linalool which had been purified by fractionated distillation. We then 
were of opinion that only during saponification in a closed vessel part of the linalool 
was decomposed owing to the heating under pressure and that the saponification 
number found in this way was but illusory. According to Niviére’s experiment, it 
would seem, however, as if linalool purified by distillation still contained small 
amounts of esters, and that pure linalool is not attacked, even when heated under 
pressure; for, after one sample had shown the same saponification value in either way 
of saponification, the same linalool, upon rectification with steam in the presence of 
a little alkali, showed no further absorption of alkali, neither when heated in an open 
nor in a closed vessel. Furthermore, the same saponification value was found for 
pure linalyl acetate in either way of heating. From his experiments, Niviére draws the 
conclusion that the increase of the ester value when heating under pressure is not due 
to the action of alkali on linalool, but probably to the influence of other bodies, such as 
aldehydes. He finds this supposition confirmed in that, after adding 2 p.c. of oenanthol 
to linalyl acetate, the ester value under pressure was 2,0 higher than that found in the 
usual way of saponification. 
Determination of the “hydrogen number” of volatile oils. 
In order to estimate certain volatile oils, A. R. Albright*) determines their hydrogen 
number’) in a complicated shaking apparatus, which he describes minutely and of which 
he gives some illustrations. By hydrogen number he understands the number of cc. of 
hydrogen which, at 0° and 760 mm. pressure, are taken up by 1 g. of oil during the 
1) Bull. Soc. chim. IV. 15 (1914), 677. — *) Gildemeister and Hoffmann, The Volatile Oils, 2.4 ed., vol. I, 
p. 572. — *) Report October 1895, 25. — *) Journ. Americ. Chem. Soc. 86 (1914), 2188. — 5) Comp. S. Fokin, 
Chem. Zentralbl. 1908, II. 2039. 
