Creosote gives a blue colour with ferric chloride solution; and the exceedingly pungent vapours evolved upon heating a residue containing capsicum are equally characteristic. The presence of tannin in distilled spirits, which is mostly derived from their preservation in casks, is recognised by the formation of a bluish-black colour upon the addition of ferric solutions. The identification of the various ethylic and amylic ethers used in the preparation of factitious liquors is a matter of some difficulty. Their presence is most readily detected by means of their characteristic odour, which is developed upon adding a little sodium hydroxide to the sample, evaporating the mixture over the water-bath almost to dryness, and then adding a small quantity of sulphuric acid. Another means of ascertaining the nature of the organic ethers present in spirits is to first remove the ethylic alcohol contained by a partial distillation with an alkaline solution, and then acidulate the remaining liquid with sulphuric acid, and repeat the distillation, when the volatile fatty acids originally contained in the ethers will be found in the distillate; their identity is to be established by means of their characteristic properties. Nitrous ether (which compound is not contained in genuine liquors) may be detected by partially distilling the sample and adding a mixture of potassium iodide, starch paste, and acetic acid to the first portion of the distillate, the production of a blue colour indicating its presence. As previously remarked, the exercise of the ordinary senses is frequently of greater value in judging the quality of liquors than the results of chemical tests. Many of the organic ethers employed in the manufacture of artificial liquors are identical with those contained in the genuine article, and it is obvious that, in such instances, no distinction can be made between them. FOOTNOTES: [111] ‘Nahrungs u. Genussmittel,’ 1st part, p. 187. [112] ‘Comptes Rendus,’ 102, p. 217-219. [113] Am. Chem. 1876, p. 46. [114] Blyth, op. cit. [115] ‘Wieder die Nahrungsfälscher,’ 1881, p. 105. [116] See Report by Dr. F. E. Engelhardt, New York State Board of Health, 1882. [117] Hager’s ‘Untersuchungen.’ [118] ‘Berichte,’ 1882, pp. 1370, 1661. WATER.