Tyrian purple in antiquity because the colour did not easily fade, but instead became brighter with weathering and sunlight. Its significance is such that the name Phoenicia means 'land of purple.' It came in various shades, the most prized being that of "blackish clotted blood". Tyrian purple was expensive: the 4th-century-BC historian Theopompus reported, "Purple for dyes fetched its weight in silver at Colophon" in Asia Minor. The expense meant that purple-dyed textiles became status symbols, whose use was restricted by sumptuary laws. The most senior Roman magistrates wore a "toga praetexta", a white toga edged with a stripe of Tyrian purple.
Sulfur dye rubbing. The dyes are bleached by hypochlorite bleach. Due to the highly polluting nature of the dye-bath effluent, sulfur dyes are being slowly phased out in the West but they are used on a large scale in China. Recent advances in dyeing technologies have allowed the substitution of toxic sulfide reducing agents. Glucose in basic solution is now used and both low sulfide and zero sulfide products are available. Future developments in the field of reducing dye levels by means of electro-chemical processes are promising. Sulfur dye Sulfur dyes are the most commonly used dyes manufactured for cotton in terms