On an improved absorption apparatus for use in the analysis of essential oils

Abstract

Meeting, i4pril 4, 1900.) ABSORPTION methods involving the removal of certain active constituents of essential oils by means of appropriate reagents, and the subsequent measurement of that portion which remains unabsorbed, are of very frequent application in laboratories where these oils are examined. As examples, the estimation of citral in lemon and lemongrass oils, cinnamic aldehyde in oil of cassia, and eugenol in oil of cloves, may be mentioned. The instrument almost invariably used for such determinations is a simple glass flask capable of holding about 200 C.C. Its neck has such a capacity that it will hold 25 C.C. of the oil, and the space between the zero and the 25 C.C. mark is graduated ink -ths, and sometimes &ths, of a C.C. This piece of apparatus is known as a Hirschsohn flask, and there are many objections to be urged against its use. I n the first place, it is practically impossible to treat the oil under examination with a second quantity of the reagent, or to wash i t ; it is, moreover, impossible, as a rule, to shake the mixture in the flask with sufficient vigour for fear of obtaining an emulsion, which will not readily separate, and any insoluble matter, such as is frequently formed on shaking the oil with the necessary reagents, accumulates at the junction of the two li.quids, thus obscuring the meniscus and reducing the accuracy of the reading, an error which is further increased by the closeness of the graduations, due to the width of the neck. I t was to obviate to some extent these objections that we devised the piece of apparatus represented in the accompanying figure.