This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
This volatile oil is obtained by distilling the orange flowers with water, when it separates upon the surface in small portions, from the orange-flower water. The flowers of the sweet orange, from which the oil neroli petale is obtained, are less aromatic than the flowers of the bitter orange, which yield the oil neroli bigarade; however, petale is considered superior, and commands a higher price than blgarade. Pure oil of neroli is of brownish hue, a bitterish aromatic taste, neutral to test paper, and of 0.889 specific gravity at 11° 0. (51.8° F.). The odor of the volatile oil differs somewhat from that of orange flowers and of distilled orange-flower water. The oil dissolves, according to Zeller, in from one to three parts of alcohol, specific gravity 0.850, the solution becoming opalescent or turbid with more alcohol. Iodine acts energetically upon neroli oil, colored vapors being given off; sulphuric acid colors it dark orange-red or red-brown; nitric acid changes the color to yellow and rust-brown. The commercial oil is usually yellowish or reddish-yellow, and is frequently adulterated with oil of berga-mot, and orange leaves (petitgrain). Old resinified oil is less fragrant, but may, in a measure, be restored by rectification with water (N. D.). Positive tests, to prove those adulterations, are not known; the cultivated nasal faculties alone may detect it. Oil of neroli should be kept well stoppered in a cool place.