H2NCNHCH2CHZSH-% J/?(HZN CN HCH2CH2S-), Vvi nitroprusside test for a thiol, shows a peak in the infrared at 4.03 I.((SH), and reacts with ammoniacal silver nitrate solution to form a black precipitate of silver sulfide, indicative of a thiourea.'Compound V and related mercaptoethylthioureas which were obtained were generally accompanied by their corresponding disulfides. The thiol forms, when isolated, were found difficult to ...