What Is Sodium Molybdate?
Sodium molybdate, a sodium salt of molybdic acid where molybdenum is bonded to an oxygen atom, often appears as sodium molybdic acid dihydrate. This white powdery solid is produced by reacting sodium hydroxide with molybdenum oxide.
It is recognized as a hazardous substance under various safety laws. Special caution is needed as it can explode upon contact with molten magnesium.
Uses of Sodium Molybdate
Sodium molybdate is used extensively as a component in antifreeze solutions, rust inhibitors, coloring agents for inorganic pigments, dye mordants, metal surface treatments, and the ceramics industry. As a fertilizer, it provides essential molybdenum for plant nitrogen fixation, nitrate reduction, and vitamin C synthesis. However, excessive use can lead to copper deficiency in cattle.
Properties of Sodium Molybdate
1. Physical Properties
Also known as disodium molybdate or sodium orthomolybdate, it has a chemical formula of MoNa2O4, a molecular weight of 205.916, a CAS number of 7631-95-0, and a density of 3.78 g/cm3. It is a nonflammable, odorless white solid.
2. Chemical Properties
It melts at 687℃ and is highly soluble in water (84g/100mL at 100℃). Upon heating, it decomposes, emitting toxic fumes and reacting violently with halogens, which may lead to fire or explosion risks. Reduction occurs when reacted with sodium borohydride.
Other Information on Sodium Molybdate
1. Safety
Toxic if ingested, it can irritate the skin, eyes, and respiratory tract. It poses risks of hereditary diseases, carcinogenicity, and germ cell mutagenicity, and could adversely affect fertility or the fetus. Long-term exposure may lead to systemic toxicity, and testicular, and kidney damage. Environmental toxicity data is currently lacking.
2. Disposal
Disposal must comply with legal and local regulations, preferably managed by a licensed industrial waste disposal contractor. Containers should be thoroughly cleaned and either recycled or disposed of as per guidelines.
3. Handling
Ensure good ventilation, especially in dust-prone areas, and wear appropriate protective gear. Avoid ingestion and ensure thorough washing after handling. Immediate rinsing is advised if contact occurs with skin or eyes.
4. Storage
Store in a dry, well-ventilated area away from oxidizers and halogens, ensuring containers are sealed. The storage area should be cool, dark, and equipped for handling hazardous substances.
5. Manufacturing Method
Sodium molybdate is produced by dissolving molybdenum oxide (VI) in heated sodium hydroxide, followed by crystallization and filtration, with heating to 100°C producing the anhydrous form.