By the kind assistance of Mr. F. G. Warrick of Nice, we have obtained a sample of Bigarade Neroli of guaranteed purity, to which the following observations relate. It is of a brownish hue, most fragrant odour, bitterish aromatic taste, and is neutral to test-paper. Its sp. gr. at 11° C. is 0·889. When mixed with alcohol, it displays a bright violet fluorescence, quite distinct from the blue fluorescence of a solution of quinine. In oil of Neroli the phenomenon may be shown most distinctly by pouring a little spirit of wine on to the surface of the essential oil, and causing the liquid to gently undulate. The oil is but turbidly miscible with bisulphide of carbon. It assumes a very pure, intense, and permanent crimson hue if shaken with a saturated solution of bisulphide of sodium. Examined in a column of 100 mm. we observed the oil to deviate the ray of polarized light 6° to the right.
Subjected to distillation, the larger part of the oil passes over at 185°-195° C.; we found this portion to be colourless, yet to display in a marked manner the violet fluorescence and also to retain the odour of the original oil. The portion remaining in the retort was mixed with about the same volume of alcohol (90 per cent.) and some drops of water added, yet not sufficient to occasion turbidity. A very small amount of the crystalline Neroli Camphor then made its appearance, floating on the surface of the liquid; by re-solution in boiling alcohol it was obtained in crystals of rather indistinct form. The redistilled oil gave no camphor whatever.
Neroli Camphor was first noticed by Boullay in 1828. According to our observations it is a neutral, inodorous, tasteless substance, fusible at 55° C., and forming on cooling a crystalline mass. The crystallization should be effected by cooling the hot alcoholic solution, no good crystals being obtainable by slow evaporation or by sublimation. The produce was extremely small, about 60 grammes of oil having yielded not more than 0·1 gramme. Perhaps this scantiness of produce was due to the oil being a year and a half old, for according to Plisson[495] the camphor diminishes the longer the oil is kept.[496] We were unable to obtain any similar substance from the oils of bergamot, petit grain, or orange peel.
Orange Flower Water is a considerable article of manufacture among the distillers of essential oils in the south of Europe, and is imported thence for use in pharmacy. According to Boullay[497] it is frequently acid to litmus when first made,—is better if distilled in small than in large quantities, and if made from the petals per se, rather than from the entire flowers. He also states that only 2 lb. of water should be drawn from 1 lb. of flowers, or 3 lb. if petals alone are placed in the still. As met with in commerce, orange flower water is colourless or of a faintly greenish yellow tinge, almost perfectly transparent, with a delicious odour and a bitter taste. Acidulated with nitric acid, it acquires a pinkish hue more or less intense, which disappears on saturation by an alkali.
Uses—Oil of Neroli is consumed almost exclusively in perfumery. Orange flower water is frequently used in medicine to give a pleasant odour to mixtures and lotions.
Adulteration—The large variation in value of oil of Neroli as shown by price-currents[498] indicates a great diversity of quality. Besides being very commonly mixed, as already stated, with the distilled oil of the leaves (Essence de Petit Grain)[499], it is sometimes reduced by addition of the less fragrant oil obtained from the flowers of the Portugal or Sweet Orange. In some of these adulterations we must conclude that orange flower water participate: metallic contamination of the latter is not unknown.
Other Products of the genus Citrus.
Essence or Essential Oil of Petit Grain—was originally obtained by subjecting little immature oranges to distillation (Pomet—1692); but it is now produced, and to a large extent, by distillation of the leaves and shoots either of the Bigarade or Bitter Orange, or of the Portugal or Sweet Orange. The essence of the former is by far the more fragrant, and commands double the price. Poiteau and Risso[500] state that the leaves of the Brigaradier with bitter fruit are by far the richest in essential oil among all the allied leaves; they are obtained in the lemon-growing districts of the Mediterranean where the essence is manufactured. Lemon-trees being mostly grafted on orange-stocks, the latter during the summer put forth shoots, which are allowed to grow till they are often some feet in length. The cultivator then cuts them off, binds them in bundles, and conveys them to the distiller of Petit Grain. The strongest shoots are frequently reserved for walking-sticks. The leaves of the two sorts of orange are easily distinguished by their smell when crushed. Essence of Petit Grain, which in odour has a certain resemblance to Neroli, is used in perfumery and especially in the manufacture of Eau de Cologne.
According to Gladstone (1864) it consists mainly of a hydrocarbon probably identical with that from oil of Neroli.
Essential Oil of Orange Peel—is largely made at Messina and also in the south of France. It is extracted by the sponge-, or by the écuelle-process, and partly from the Bigarade and partly from the Sweet or Portugal Orange, the scarcely ripe fruit being in either case employed. The oil made from the former is much more valuable than that obtained from the latter, and the two are distinguished in price-currents as Essence de Bigarade and Essence de Portugal.