sulfur dye

or sul·fide dye

[ suhl-fer dahy or suhl-fahyd dahy, ‐fid ]
/ ˈsʌl fər ˌdaɪ or ˈsʌl faɪd ˌdaɪ, ‐fɪd /

noun Chemistry.

any of the class of dyes produced by heating an organic compound, as an indophenol, with sulfur or sodium polysulfide, used chiefly in dyeing cotton.