(a) in the presence of Pyridine , with Chlorosulfonic acid treatment C.I. Vat Blue 4 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 4. The above two kinds of situation after alkaline, filter out insolubles, remove Pyridine and salting out. Acetyl amino anthraquinone in condensation ago, use the above one way into leuco two sulfate, and then in the alkali solution of hydrolysis, oxidation and salting out. Note: the preparation of potassium, sodium, such as lithium, calcium, 2-Aminoethanol salt products, etc.
