Which of the following substances is used as a pigment in the dyeing and tanning industry?

Option 4 : Magnesium sulfate

The correct answer is Magnesium sulfate.

• Magnesium sulfate, MgSO₄, is a colorless crystalline substance formed by the reaction of magnesium hydroxide with sulfur dioxide and air.
• Magnesium sulfate is used in the manufacture of cement and fertilizers and in the tanning and dyeing industry.
• In medicine, it serves as a purgative. Because of its ability to absorb water readily, the anhydrous form is used as a desiccant (drying agent).

• Magnesium carbonate:
  • Magnesium carbonate, MgCO₃, occurs in nature as the mineral magnesite and is an important source of elemental magnesium.
  • It has many industrial uses as a heat insulator for boilers and pipes and as an additive in food, pharmaceuticals, cosmetics, rubbers, inks, and glass. 
• Magnesium chloride:​
  • ​Magnesium chloride, MgCl₂, a colorless, deliquescent (water-absorbing) substance employed in magnesium metal production.
  • MgCl₂ used in the manufacture of cement for heavy-duty flooring, and as an additive in textile manufacture.
• Magnesium oxide:
  • ​Magnesium oxide, commonly called magnesia, MgO. It is a white solid used in the manufacture of high-temperature refractory bricks, electrical and thermal insulators, cement, fertilizer, rubber, and plastics.
  • It is also used medically as a laxative and antacid.