A frankly red colour is inferior to one with a tinge of black. The liquid is then heated till the colour answers to expectations. Meanwhile, the flesh which necessarily adheres to the veins is skimmed off and a test is made about the tenth day by steeping a well-washed fleece in the liquefied contents of one of the vessels.
Next, five hundred pounds of dye-stuff, diluted with an amphora of water, are subjected to an even and moderate heat by placing the vessels in a flue communicating with a distant furnace. It should be soaked for three days, for the fresher the extract, the more powerful the dye, then boiled in a leaden vessel. The vein already mentioned is then extracted and about a sextarius of salt added to each hundred pounds of material. The process is described by Pliny, writing in the 1st century AD: But it is clear that the dye does not exist in the mollusc and is generated from precursors, sometimes termed chromogens, contained in the hypobranchial gland. Surviving details of the ancient process are insufficient to explain the chemistry involved and this is the subject of continuing speculation. The ancient industry was distributed world-wide. This molluscan dye has been known since pre-Roman times and in the Mediterranean region there is evidence for the industry around the 13th century B.C. This review attempts to set the record straight. The long history, stretching back well into the pre-chemical era, and embracing chemistry, biology and sociology, contains not a few misconceptions and erroneous conclusions. The colour is derived exclusively from marine shellfish of the Muricidae and Thaisidae families. Arguably, it is the oldest known pigment, the longest lasting, the subject of the first chemical industry, the most expensive and the best known. Keywords: 6,6'-dibromoindigo, 6-bromoindigo, 6,6'-dibromoindirubin, tyrindoxyl, tyriverdin, tyrindoleninone, tyrindolinone, synthesis, structure, propertiesĦ,6'-Dibromoindigo is a major component of the historic pigment Tyrian purple, also known as Royal purple, shellfish purple and Purple of the Ancients.
Tyrian Purple: 6,6'-Dibromoindigo and Related Compoundsĥ9 Swiss Avenue Watford WD18 7LL, UK tel +44 1923 241 688 fax +44 8 e-mail: 15 August 2001 /Accepted: 20 August 2001 /Published: 31 August 2001Ībstract: The genesis of the purple dye from shellfish, its composition, origin, intermediates, analysis and synthesis of the components, 6,6'-dibromoindigo, 6-bromoindigo and 6,6'-dibromoindirubin are reviewed
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