[old C.I. 1242]. A purplish red coloring matter obtained from natural litmus or synthesized by oxidizing orcinol in the presence of ammonia, lime, and potash; used as a broad indicator of pH (red at 4.5, blue at 8.3).
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[old C.I. 1242]. A purplish red coloring matter obtained from natural litmus or synthesized by oxidizing orcinol in the presence of ammonia, lime, and potash; used as a broad indicator of pH (red at 4.5, blue at 8.3).