Sodium sulphide is also known as caustic soda, smelly soda, yellow alkali, sulphide. Sodium sulphide is inorganic compound, pure sulfide is colorless crystalline powder. Strong moisture absorption, soluble in water. The aqueous solution has a strong alkaline reaction. Touching skin and hair can cause burns. So sodium sulphide is commonly known as sulfide. Sodium sulphide is slowly oxidized to sodium thiosulfate, sodium sulfite, sodium sulfate and sodium polysulfide in the air. Due to the rapid formation of sodium thiosulfate, the main product of oxidation is sodium thiosulfate. The sodium sulphide is in the air, and it is carbonated and metamorphosed, releasing hydrogen sulphide gas. Industrial sulphide is pink, red-brown, and yellow in color because it contains impurities. Gravity, melting point and boiling point are also affected by impurities