That bromine-water precipitates several volatile and fixed alkaloids from their solutions is no objection to the bromine test, for it may be applied to a distillation product, the bases having been previously fixed by sulphuric acid. Besides, the properties of tri-bromo-phenol are distinct enough, and therefore there is no valid objection to the test. It is the best hitherto discovered. There are also other reactions, such as that Millon’s reagent strikes a red--molybdic acid, in concentrated sulphuric acid, a blue--and potassic dichromate, with sulphuric acid, a brown colour--but to these there are objections. Again, we have the _Euchlorine_ test, in which the procedure is as follows:--A test-tube is taken, and concentrated hydrochloric acid is allowed to act therein upon potassic chlorate. After the gas has been evolved for from 30 to 40 seconds, the liquid is diluted with 1½ volume of water, the gas removed by blowing through a tube, and solution of strong ammonia poured in so as to form a layer on the top; after blowing out the white fumes of ammonium chloride, a few drops of the sample to be tested are added. In the presence of carbolic acid, a rose-red, blood-red, or red-brown tint is produced, according to the quantity present. Carbolic acid may be confounded with _cresol_ or with _creasote_, but the distinction between pure carbolic acid, pure cresol, and creasote is plain. § 232. =Cresol (Cresylic Acid, Methyl-phenol)=, OH / C₆H₄ . \ CH₃ --There are three cresols--ortho-, meta-, and para-. Ordinary commercial cresol is a mixture of the three, but contains but little ortho-cresol; the more important properties of the pure cresols are set out in the following table:-- +--------+-----------------+----------------+---------------------+ | | Melting-point. | Boiling-point. | Converted by fusion | | | | | with Potash into-- | +--------+-----------------+----------------+---------------------+ |Ortho-, | 31-31·5° C. | 188·0° | Salicylic Acid | | | | | (Ortho-oxybenzoic | | | | | acid). | | | | | | |Meta-, |Fluid at ordinary| 201·0° | Meta-oxybenzoic | | | temperature. | | acid. | | | | | | |Para-, | 36° | 198° |Para-oxybenzoic acid.| +--------+-----------------+----------------+---------------------+ Pure ortho-, meta-, or para-cresol have been obtained by synthetical methods; they cannot be said to be in ordinary commerce.