_Detection of alcohol or spirit of wine._--Independent of the alcohol added to assist the preservation of some oils, adulteration with alcohol frequently occurs, especially in expensive oils. With a content of not more than 3 per cent. of alcohol, it suffices to allow one to two drops of the suspected oil to fall into water. In the presence of alcohol, the drop becomes either immediately surrounded with a milky zone, or it becomes turbid or whitish after being for some time in contact with the water. Dragendorff's test is based upon the fact that oils, which are hydrocarbons, suffer no change by the addition of sodium (ten drops of oil and a small chip of sodium), while oils containing hydrocarbons and oxygenated oils cause with sodium a slight evolution of hydrogen gas, and suffer but a slight change during the first five to ten minutes of the reaction. If, however, the oil is adulterated with alcohol, not only a violent evolution of hydrogen gas takes place, but the oil in a short time becomes brown or dark brown, thickly fluid or rigid. The detection of alcohol by means of fuchsine, which has been frequently recommended, requires special precautions. It must first be ascertained that the oil is free from acids and water; if such is not the case, they must be removed by means of caustic potash. After settling, bring, by means of a dry pipette, about five cubic centimeters of the oil into a dry test-tube about ten millimeters in diameter, without moistening the walls of the upper half of the tube. Then bring, by means of a paper gutter, a few milligrammes of coarsely-powdered fuchsine into the dry part of the obliquely held tube, at a distance of one centimeter from the oil. Now heat gradually over a lamp until the tube begins to tarnish. With pure oil no evaporation is observed, but if the oil contains only 0.1 per cent. of alcohol, every speck of fuchsine will, after heating to boiling and setting aside, be surrounded by a stain produced by the alcoholic solution. The chief requirement for this test is that the oil be free from water. If such is not the case, vapors will be observed, which condense in the upper portion of the test-tube, and dissolve fuchsine, and, after flowing back, sink below the oil with a crackling noise. If the oil contains alcohol, the condensing vapors dissolve fuchsine with greater ease, and in flowing back mix without crackling.