“Otto-of-rose, when analysed, is found to consist of two ingredients: the oleoptene, which is the liquid and odoriferous part of the otto-of-rose, and the stereoptene, which is the solid and odourless part, and causes the crystallisation of the otto-of-rose. The proportion in which these two ingredients are combined in the pure otto-of-rose is more or less fixed, varying only from 10 to 15 per cent. according to the elevation of the localities in which the otto is produced. The highest proportion—15 per cent.—is found in otto-of-rose distilled in villages situated highest in the Balkans; while the villages down in the plains produce otto-of-rose containing only 10 to 11 per cent. of stereoptene. We have lately made experiments to distil these two ingredients separately, but they can best be separated from each other by a very simple physical process. The average proportion of these two ingredients in our stocks during the last five years has been about 12½ per cent. of stereoptene and 87½ per cent. of oleoptene. “The oil usually employed for the adulteration of otto-of-rose is the geranium oil (_Palagonium Radula_) known to the trade as Turkish geranium oil. This oil is made in India and is sold in Constantinople. Formerly they used this oil as adulterant in its crude state, but now it is generally refined in rose-water or rose-flower before it is used. No matter how well refined, it is impossible to put 5 per cent. of it in otto-of-rose without changing the freezing point of the otto, its specific gravity, and the proportion in which the stereoptene and oleoptene are combined. Geranium oil contains no stereoptene, and in consequence does not crystallise. In the best refined geranium oil the specific gravity is fully ·880—a difference in weight of about eighteen points. All this helps to detect its presence in otto-of-rose. It can also be detected by means of the iodine as well as the nitric acid tests. The presence of geranium oil in otto-of-rose lowers its freezing point, renders its specific gravity heavier, and changes the proportion in which the oleoptene and stereoptene are combined. [Illustration: The Rose-fields near Kazanlik.] “In order to rectify these defects, the use of spermaceti, paraffin, and alcohol have often been resorted to, but the presence of all these three substances can be discovered without any difficulty. The crystals of both spermaceti and paraffin are entirely different from the crystals of the stereoptene of otto-of-rose, and otto-of-rose containing any proportion of either will lose, when congealed, its sharp-pointed, needle-like crystals. Besides, paraffin and spermaceti being fatty oils, are much heavier, and in time will settle at the bottom. Furthermore, they are not volatile as stereoptene. The presence of alcohol is detected either by the use of double distilled water or of pure glycerine.”