any of various blue dyes which are applied or remain fast in alkaline conditions; spec. any of a series of sodium salts of phenylated rosaniline sulphonic acids, used as indicators and as pigments for printing inks
3. REAGENTS ... 3.3 Phenolphthalein, 10 g/l solution in 95 to 96 % ethanol (v/v) or alkali blue 6B or thymolphthalein, 20 g/l solution in 95 to 96 % ethanol (v/v). In the case of strongly coloured oils, alkali blue or thymolphthalein shall be used.
1.2. Reagents ... 1.2.3. Phenolphtalein, 10 g/l solution in 95 to 96% ethanol (v/v) or alkaline blue, (in the case of strongly coloured fats) 20 g/l solution in 95 to 96% ethanol (v/v).
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alkaline - having the properties of an alkali, that is or contains an alkali
