3-Cyan0-4-hydroxy-1.2, Bthiadiazole has been obtained from the reaction of potassium cyanide and sulfur dioxide at 25-85'in the absence of hydroxylic solvents. The structure was elucidated by degradation to diethylaminoacetamide and to N-sulfamoyloxamic acid dipotassium salt, and by independent synthesis from isonitrosocyanoacetamide and sulfur dichloride. Various 3-hydroxy-1, 2, 5-thiadiazole derivatives were prepared including ...