Good oil of cloves should have a specific gravity of 1.067 at 15 degrees C., and should be freely soluble in alcohol at 90 per cent. An adulteration by turpentine would lower the specific gravity and diminish the solubility in alcohol. Eugenol is a strongly refractive liquid with the characteristic smell and the burning taste of cloves, and by exposure to the air it becomes brown; on fusion with caustic potash it yields protocatechuic acid convertible into vanillin by action of potassium permanganate. Eugenol is also found in pimento and in the leaves of cinnamon and of many other trees and has been artificially produced by the action of sodium amalgam on coniferyl alcohol. Pure eugenol has a specific gravity of 1.072 at 15 degrees; its boiling point is 253 degrees to 243 degrees C., and it forms a clear solution in 1 per cent. of caustic potash solution. Clove oil has been found to contain some salicylic acid, which gives the greenish blue coloration when it is brought in contact with an alcoholic solution of perchloride of iron, and produces the intense violet color when it is agitated with metallic reduced iron. This acid may be isolated by agitating the oil with a solution of carbonate of ammonia. Caryophyllin (C_{10}H_{18}O), a neutral, tasteless, inodorous substance, isomeric with common camphor, crystallizable in prismatic needles, has also been found in cloves by extracting with ether cloves previously deprived of the greater part of their essential oil by a little alcohol. Cloves also contain 16 per cent. of a peculiar tannic acid, 13 per cent. of gum, and about 18 per cent. of water and extractive matter. The chemical composition of cloves differs to quite an extent in the different countries where they grow—Amboina, 19 per cent.; Zanzibar, 17.5 per cent. Water, 11.00 to 2.75 Ash, 13.00 to 5.00 Volatile Oil, 21.00 to 9.00 Fixed Oil and Resin, 11.00 to 4.00 Crude Fiber, 10.00 to 6.00 Albuminoids, 8.00 to 4.00 Coffee oil is least volatile of any essential oil and is obtained from the flower buds and the flower stalks of cloves by aqueous distillation. This distillation is largely carried on in England, and the proportion of oil may amount to 16 or 20 per cent., but, to extract the whole, distillation must be long continued; the water being returned to the same material. The oil is a colorless or yellowish liquid like all clove oil, with a powerful odor and flavor of cloves, varying in specific gravity from 1.046 to 1.058. It combines well with grease, soap, and spirits, and is largely used in perfumery, and in Germany it is often adulterated with carbolic acid (phenol). ------------------------------------------------------------------------ [Illustration: GINGER. (Amomum Zingiber) 1 Leaf stalk 2 Flowers 3 Cochin ginger 4 African 5 Jamaica]