Oil of Cit′ron. Syn. Essence of citron; Oleum citri, L. From the lees of citron juice; or, from the peels, as oil of lemons or bergamot. The last generally goes by the name of oil of cedrat. Both are fragrant. (See above.)
Oil of Citron-flowers. Syn. Oleum citri florum, L. Amber-coloured; highly fragrant. Prod. 60 lbs. yield 1 oz.
Oil of Cloves. Syn. Essence of cloves; Oleum caryophyllorum, O. caryophylli (B. P., Ph. L. E. & D.), O. Eugeniæ c. (Ph. D. 1826), L. From the unexpanded flowers (cloves) of the Caryophylus aromaticus, or Molucca clove-tree, soaked for some time in salt and water, and then submitted to distillation; the distilled water, after having deposited its oil, being returned 3 or 4 times into the still, and again ‘worked off’ from the same materials. Nearly colourless, when recent, gradually becoming pale yellow and ultimately light brown, by age; highly aromatic, with the characteristic odour and flavour of cloves. It is the least volatile of all the essential oils. Sp. gr. 1·055 to 1·061 (1·034 to 1·061, B. P.). Prod. 16% to 22%.
Pur. Oil of cloves is frequently adulterated with inferior essential oils, especially with those of pimento, pinks, and clove-gilly flowers, and, occasionally, with castor oil.—1. Pure oil of cloves forms a butyraceous coagulum when shaken with pure liquor of ammonia, which crystallises after fusion by a gentle heat.—2. Treated with an alcoholic solution of potassa,
it entirely congeals into a crystalline mass, with total loss of its characteristic odour.—3. Shaken with an equal volume of strong caustic soda lye, it forms, on repose a mass of delicate lamellar crystals—4. Solution of chromate of potassa converts it into brown flakes, whilst the salt loses its yellow colour.—5. Chlorine turns it first green, and then brown and resinous.—6. Nitric acid turns it red, and a reddish-brown solid mass is formed; with heat, it converts it into oxalic acid.—7. It dissolves freely in sulphuric acid (oil of vitriol), yielding a transparent, deep reddish-brown solution, without any visible decomposition.—8. Mixed, gradually, with about 1⁄3rd of its weight of oil of vitriol, an acid liquor is formed, together with a resin of a rich purple colour, which, after being washed, is hard and brittle, and forms a red tincture with rectified spirit, which is precipitated of a blood-red colour by water.—9. It dissolves iodine freely, without any marked reaction.—10. It dissolves santaline freely.—11. Mix one drop of the oil with a small trace of solution of aniline by means of a glass rod, and then shake with 5 or 6 c.c. of distilled water. By the addition of a few drops of sodium hypochlorite to the mixture the characteristic blue coloration due to phenol will be developed in a few minutes, if the adulterant be present; whereas with the pure oil nothing but the purplish-violet colour of aniline will be perceived. Stirring or shaking must be avoided after the addition of the hypochlorite. The presence of 1 per cent. of phenol can thus be demonstrated in one drop of the oil.
Obs. Clove oil contains a heavy oil, sp. gr. 1·079 (caryophyllic acid), and a light oil, sp. gr. ·918 (clove hydrocarbon); by rectification, much of the light oil is lost, and the product becomes denser. (1·361—Bonastre.)
Oil, Cog′nac. See Oil, Grape (below).
Oil of Copai′ba. Syn. Oil of capivi; Oleum copaibæ (B. P., Ph., L. & E.), L. 1. (Ph. E.) Balsam of capivi, 1 oz.; water, 11⁄2 pint; distil, returning the water into the still, until oil ceases to pass over.
2. (Wholesale.) From the crude oil which separates during the manufacture of ‘specific solution of copaiba’ and ‘soluble capivi,’ by distillation along with a little salt and water.
Pur., &c. Colourless when pure; that of commerce has frequently a greenish tinge, derived from the copper utensils; odour, not disagreeable when recent. Sp. gr. ·876 to ·878. Prod. 50% to 55%. When adulterated with oil of turpentine, its solubility in rectified spirit is greatly diminished, and the solution is turbid.—Dose, 10 to 15 drops, in sugar; in the usual cases in which copaiba is ordered. 20 to 60 minims, three times a day (B. P.).