Used in the production of ceramic glazes and glass to improve hardness and durability. Acts as a flux to lower melting temperature during firing. Common in manufacturing ferrites for electronic components like inductors and transformers. Added to brick and tile formulations to reduce efflorescence. Employed in rat poisons and pesticides due to its toxicity to rodents. Used in some types of welding fluxes and in the purification of molten metals. Occasionally found in specialty optical glasses and radiation shielding materials.