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The crude diaminoresorcinol (57.0 g), from Step A, containing the Pd/C catalyst, is dissolved in 400 g of 6% aqueous HCl at 80° C. The catalyst is removed by filtration. An additional 50.0 g of concentrated HCl containing 1.5 g of stannous chloride dihydrate is added to the diaminoresorcinol mixture along with 5.0 g of activated carbon. The solution is heated at reflux for 15 minutes and then the carbon is removed by filtration. The filtrate is cooled to 0° C. to allow crystallization of the product. The resulting white precipitate is isolated by filtration under a purge of dry nitrogen. This filter cake is then dried in vacuo at 40° C. to a constant weight to yield 48.7 g of essentially pure (99.8%) 4,6-diaminoresorcinol dihydrochloride having a m.p. of >300° C. Elemental Anal. calc'd for C6H10Cl2N2O2 (213.0643): C, 33.82; H, 4.73; Cl, 33.28; N, 13.15; 0, 15.02, found: C, 33.6; H, 4.64; N, 13.20.

1. customThe catalyst is removed by filtration
2. additionAn additional 50.0 g of concentrated HCl containing 1.5 g of stannous chloride dihydrate is added to the diaminoresorcinol mixture along with 5.0 g of activated carbon
3. temperatureThe solution is heated
4. temperatureat reflux for 15 minutes
5. customthe carbon is removed by filtration
6. customcrystallization of the product
7. customThe resulting white precipitate is isolated by filtration under
8. customa purge of dry nitrogen
9. customThis filter cake is then dried in vacuo at 40° C. to a constant weight