2-amino-5-mercapto-1 3 4-thiadiazole solubility July 8, 2019 16 32 64 128 2-amino-5-mercapto-1 3 4-thiadiazole 2-amino-5-methyl-1 3 4-thiadiazole 2-acetylamino-5-mercapto-1 3 4-thiadiazole