C6h2(Oh)2[I.2], C]] a vegetable dyestuff formerly prepared from madder root (Rubia tinctorum) which contains a glucoside ruberythric acid (C26H28014).
The melt is dissolved in water and the dyestuff is liberated from the sodium salt by hydrochloric or sulphuric acid, or is converted into the calcium salt by digestion with hot milk of lime, then filtered and the calcium salt decomposed by acid.
Its value as a dyestuff depends on its power of forming insoluble compounds (lakes) with metallic oxides.
Phenanthrenequinone).Alizarin black,C l oH 4 (OH) 2 0 2 NaHS03, the sodium bisulphite compound of 7.8 dioxy-anaphthoquinone, is a dyestuff used for printing on cotton in the presence of a chromium mordant The naphthoquinone is prepared by the action of zinc and concentrated sulphuric acid on a-dinitronaphthalene.
FUCHSINE, or Magenta, a red dyestuff consisting of a mixture of the hydrochlorides or acetates of pararosaniline and rosaniline.