1475. To Detect the Presence of Fatty Oil and Resins in Essential Oils

1475. To Detect the Presence of Fatty Oil and Resins in Essential Oils. The presence of fatty oil, resin, or spermaceti, may be readily detected by placing a single drop of the suspected oil on a piece of white paper, and exposing it for a short time to heat. If the oil under examination be pure, it will entirely evaporate; but if it be adulterated with one of these substances, a greasy or translucent spot will be left on the paper. These substances also remain undissolved when the oil is agitated with three or four times its volume of strong rectified spirit.

1476. To Detect the Presence of Alcohol in Essential Oils

1476.    To Detect the Presence of Alcohol in Essential Oils. The presence of alcohol or rectified spirit may be detected by agitation with the oil a few small fragments of dried chloride of calcium. These will remain unaltered if the oil be pure, but will dissolve in one containing alcohol, and the resulting solution will form a distinct stratum at the bottom of the vessel. The milkiness and loss of volume, when such an oil is agitated with a little water, is another test of the presence of spirit. A more delicate test of the presence of alcohol in an essential oil than the preceding, is effected by potassium. Place 12 drops of the oil on a perfectly dry watch-glass, and put a piece of potassium, the size of an ordinary pin's head, in the middle of it. If the potassium remains unchanged for 12 or 15 minutes, no alcohol is present; but if it disappears after 5 minutes, the oil contains at least 4 per cent, of alcohol; if it disappears in less than 1 minute, it proves the presence of not less than 25 per cent, of alcohol. This species of adulteration is very common. It is a very general practice of the druggists to add strong rectified spirit to their essential oils, to render them transparent, especially in cold weather. Oil of cassia and oil of cinnamon are nearly always so treated by them.

1477. To Detect the Admixture of one Essential Oil with Another

1477.    To Detect the Admixture of one Essential Oil with Another. The admixture of an inferior essential oil with another more costly, is readily detected by a connoisseur or expert, by placing a drop or two on a piece of clean blotting-paper, shaking it in the air, and smelling it occasionally. The difference of the odor at the beginning and towards the end of the evaporation will show the adulteration, especially if the adulterant be oil of turpentine. This last may also be detected by remaining undissolved when the oil is agitated with about thrice its volume of strong rectified spirit. Highly rectified oil of turpentine is very largely used to adulterate the stronger scented essential oils. Foreign oil of lavender and oil of peppermint, for example, are usually compounds of 1 ounce of the genuine oil with 9 ounces of oil of turpentine. Even American and English oil of peppermint are adulterated with 1/3 part rectified spirit, besides a considerable quantity of oil of spearmint, and often turpentine.