(_a_) The colour is red; the dye is rhodamine or fuchsine, or one of their allies. (_b_) It is green; the dye is malachite green, brilliant green, or one of their allies. (_c_) It is blue; the dye is night blue, Victoria blue, or one of their allies. (_d_) It is violet; the dye is methyl violet, crystal violet, or one of their allies. If the original colour does not reappear even with chromic acid, it was in most cases a yellow or a brown, referable to auramine, chrysoidine, Bismarck brown, thioflavine, or one of their allies. If the tannin reagent produces no precipitate, reduce with hydrochloric acid and zinc, or ammonia and zinc, and neutralise and filter as in the case of a basic dye. The solution when dropped on to white filter paper may be bleached (_a_), may have become a brownish red (_b_), may have been imperfectly and slowly bleached (_c_), or may have undergone no change (_d_). (_a_) If the colour quickly returns the dye is azurine, indigo-carmine, nigrosine, or one of their allies. If it returns only on padding with a 1 per cent. solution of chromic acid, warming, and holding over ammonia, some of the dye is dissolved in water mixed with concentrated hydrochloric acid, and shaken up with ether. If the ether takes up the dye, we have aurine, eosine, erythrine, phloxine, erythrosine, or one of their allies. If it does not, we have acid fuchsine, acid green, fast green, water blue, patent blue, or one of their allies. If the colour never returns, heat some of the dye on platinum foil. If it deflagrates with coloured fumes, the dye is aurantia, naphthol yellow S., brilliant yellow, or one of their allies. If it does not deflagrate, or very slightly, dissolve a little of the dye in one hundred times its weight of water, and dye a cotton skein in it at the boil for about fifteen minutes. Then rinse and soap the skein vigorously. If the dyeing is fast with this treatment we have a substantive cotton yellow or thiazine red; if it is not, we have an ordinary azo dye. (_b_) The dye is an oxyketone, such as alizarine. (_c_) The dye is thiazol yellow, or one of its allies. (_d_) The dye is thioflavine S., quinoline yellow, or one of their allies. If the dye is not stripped by alcohol and water, it is either inorganic or an adjective dye, such as logwood black, cutch, fustic, etc.; and we proceed according to the colour as follows:--