2-(2,5-Dihydroxyphenyl)-2-thiopseudourea monohydrochloride 6274-93-7 NSC 33521 Pseudourea, 2-(2,5-dihydroxyphenyl)-2-thio-, hydrochloride Pseudourea, 2-(2,5-dihydroxyphenyl)-2-thio-, monohydrochloride USAF PD-17