Indigo and shellfish purple dye

Figure 4. H SO (cone,) solutions of indigo (----) and shellfish (----) purple dye...

Textile dyes were, until the nineteenth century invention of aniline dyes, derived from biological sources plants or animals, eg, insects or, as in the case of the highly prized classical dyestuff Tyrian purple, a shellfish. Some of these natural dyes are so-caUed vat dyes, eg, indigo and Tyrian purple, in which a chemical modification after binding to the fiber results in the intended color. Some others are direct dyes, eg, walnut sheU and safflower, that can be apphed directly to the fiber. The majority, however, are mordant dyes a metal salt precipitated onto the fiber facUitates the binding of the dyestuff Aluminum, iron, and tin salts ate the most common historical mordants. The color of the dyed textile depends on the mordant used for example, cochineal is crimson when mordanted with aluminum, purple with iron, and scarlet with tin (see Dyes AND DYE INTERMEDIATES). 

The chemistry of colorants, particularly in the dyeing of textiles, has a long and rich history. There are indications that the art of dyeing was practiced as early as 3000 B.C.E. in China and Egypt [21]. The colorants used were obtained from natural sources. Examples include blue indigo from the indigo plant, reds fi om the root of madder, yellows and reds from saffiower, and lyrian Purple produced by the Phoenicians from shellfish [22]. 

Tyrian Purple the most expensive dye (main component is dibromo indigo), historically also called royal purple, is obtained from purpura shellfish Murex brandaris) and is substituted by synthetic dye today (12000 mollusks were necessary to obtain 1.4 g of the dye). 

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