These colors are not suitable for converting white wine into red, but they can be used for giving wines a faint red tint, for darkening pale red wines, and in making up a factitious bouquet essence, which is added to red wines. The most suitable methods for the detection of magenta are those given by Romei and Falieres-Ritter. If a wine colored with archil and one colored with cudbear are treated according to Romei's method, the former gives, with basic lead acetate, a blue, and the latter a fine violet precipitate. The filtrate, if shaken up with amylic alcohol, gives it in either case a red color. A knowledge of this fact is important, or it may be mistaken for magenta. The behavior of the amylic alcohol, thus colored red, with hydrochloric acid and ammonia is characteristic. If the red color is due to magenta, it is destroyed by both these reagents, while hydrocholoric acid does not decolorize the solutions of archil and cudbear, and ammonia turns their red color to a purple violet.

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