Insoluble sulfur, also known as precipitated sulfur, is a finely divided form of sulfur that is insoluble in water and most organic solvents. It is used in the vulcanization of rubber to improve elasticity, strength, and resistance to abrasion. This form of sulfur is preferred for its purity and ease of dispersion in rubber compounds. Insoluble sulfur is also utilized in the production of pharmaceuticals, pesticides, and as an ingredient in some types of batteries due to its unique chemical and physical properties.