disodium 5,5',7,7'-tetrabromo[2,2'-bi-1H-indole]-3,3'-diyl disulphate

Preparation

(a) in the presence of Pyridine , with Chlorosulfonic acid treatment C.I. Vat Blue 5 leuco; (b) in the Pyridine with metal (such as copper, iron, zinc, etc) and Sulfur trioxide source (such as Sulfur trioxide, Chlorosulfonic acid or Methyl chlorosulfonate, etc.) processing ?C.I. Vat Blue 5. The above two kinds of situation after alkaline, filter out insolubles, remove Pyridine and salting out.

Properties and Applications

blue. Light gray powder. Soluble in water is blue, the acid brilliant is basic, in light and acid under the action of rapid decomposition, make the solution is blue. In concentrated sulfuric acid for cyan. When color oxidation more difficult, low temperature issued color not fully. Mainly used for cotton fabric dyeing and printing, also used for silk and polyester/cotton blended fabric dyeing and printing, but also can be used to hand printed.