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The crude dihydrochloride salt of 4,6-diaminoresorcinol (57.0 g) containing 10% Pd/C catalyst is dissolved in 400 g of 6% (by weight) aqueous HCl at 80° C. The catalyst present is removed by filtration. An additional 50.0 g of concentrated HCl containing 1.5 g of stannous chloride dihydrate is added to the product mixture along with 5.0 g of activated carbon. The solution is heated at reflux for 15 minutes and the carbon is then removed by filtration. The filtrate is cooled to 0° C. to allow crystallization of the monomer. The resulting 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 an m.p. of >300° C. with decomposition. Elemental Anal. calc'd for C6H10Cl2N2O2 (213.0642): C, 33.82; H, 4.73; Cl, 33.28; N, 13.15; O, 15.02, found: C, 33.6; H, 4.64; N, 13.20.

1. customThe catalyst present 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 product mixture along with 5.0 g of activated carbon
3. temperatureThe solution is heated
4. temperatureat reflux for 15 minutes
5. customthe carbon is then removed by filtration
6. customcrystallization of the monomer
7. customThe resulting 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