Description 6,6′-Dithiodinicotinic acid is reported as sulphydryl reagent. 6,6′-Dithiodinicotinic acid is reported to react with thiols, to afford a disulfide and 6-mercaptonicotinic acid. Interaction of 6,6′-dithiodinicotinic acid with the homogenates of Ehrlich ascites cells has been reported.6,6′-Dithiodinicotinic acid may be employed as:specific thiol blocker to investigate the radioprotective effect of mercaptoethylamine on the thiol level of the outer cell membrane of the Ehrlich ascites tumor cellsmodifier to investigate the polar microenvironment around the reactive Cys283 of rabbit muscle creatine kinasedipyridyl-dithio substrate to evaluate the protein disulfide-thiol interchange activity of the auxin stimulated NADH: protein disulfide reductase (NADH oxidase) of soybean plasma membraneswater-soluble reagent in a study for introducing, in buffered saline, a reactive sulfhydryl group on water-soluble molecules bearing an alkyl-amino groupchromogen for sulfhydryl groups in the Ellman method for cholinesterase determinationsspectrophotometric determination of thiols and of total glutathione in human blood