It was found that, after fractional distillation, the product of the industrial synthesis of tert-dodecyl mercaptan constituted a mixture of tertiary C12H25SH isomers (95-96%), C12H24 olefins (3-4%), and disulfides (1.5-2%). The still bottoms (bp > 250degreesC) contained high-boiling-point >C-13 mercaptans, sulfides, and disulfides (25, 26.3, 8.6%, respectively) and about 24% compounds of unknown structure, along with C12H25SH isomers (8%) and C12H24 olefins (8%).