1.1 This test method covers the determination of assay on mercaptobenzothiazole (MBT) sulfenamides. It is based on a titration of the basic amines liberated upon reduction of the sulfenamides with hydrogen sulfide gas (H2S), or 2-mercaptobenzothiazole.1.2 Any free amine (HNR2) or weak acid salts of the corresponding amine (HXHNR2) are titrated prior to reduction. This titer is used to calculate percent basic impurity (as free amine) in the sa