[Doni Mac]

How to remove the Black dye/colour treated over paper with sulfite/sulphide solution compound to get opaque black.
Any one can tell me the methods 
OR
How to Prepare Thiourea Dioxide…
I need the formula and method of preparation.. One thing I know is that, this will exist as dioxide in Thio for little time and should be used for removal of black dye/colour due to sulfite compound treatment on paper. I need the Balanced formula
I was suggested but I couldn't seen any where in the book or net...!