Which one of the following is used as a mordant in dyeing and tanning industry ?

Magnesium sulphate, commonly known as Epsom salt (MgSO₄·7H₂O), is widely used as a mordant in the dyeing and tanning industries. A mordant acts as a chemical bridge between dye molecules and fabric or leather fibers, ensuring color permanence and preventing fading [t4]. In natural dyeing, magnesium sulphate facilitates 'one-bath' dyeing processes by increasing the uptake of pigments into the material [t1][t2]. Specifically, in the tanning industry, it is used in the ecoprinting process on leather to enhance the adhesion of natural dyes and stabilize colors [t4]. While other magnesium salts like magnesium chloride are mentioned in industrial contexts, magnesium sulphate is the primary salt recognized for its role as a simultaneous mordant (meta-mordant) to provide effective deep dyeing [t5]. Its metal ions (Mg²⁺) bind with pigments to form complex salts that fix the dye to the tissue molecules [t4].

Sources

1. [1] https://iojs.unida.ac.id/index.php/IJAR/article/download/606/240/