What Is Sodium Bisulfate?
Sodium bisulfate, also known as sodium hydrogen sulfate, is a white crystalline salt composed of sodium and hydrogen sulfate.
Its chemical formula is NaHSO4, with a molecular weight of 120.06, and its CAS number is 7681-38-1. Another term for sodium bisulfate is sulfuric acid, monosodium salt.
Uses of Sodium Bisulfate
Sodium bisulfate serves primarily as a fluxing agent in the analysis of minerals and poorly soluble salts, and for cleaning platinum equipment. Its efficacy stems from the ability of hydrogen sulfate to transform into a soluble sulfate upon melting with insoluble salts, a process known as hydrogen sulfate melting.
Additionally, sodium bisulfate functions as a food additive, enhancing pancake mixes, beverages, dressings, sauces, and meat processing, and preventing browning in fresh-cut produce. It offers a preferred alternative to citric, malic, or phosphoric acid for reducing pH without increasing acidity, also serving as an anti-browning agent.
Its other uses include metal surface treatment, bitumen treatment agents, water disinfectants, pH adjusters, and applications in the soap, brick, cement, and papermaking industries.
Properties of Sodium Bisulfate
Sodium bisulfate, lacking a boiling or melting point, decomposes into Na2S2O7 at approximately 315°C. With a density of 2.74 g/cm3, it is a stable, hygroscopic acid salt, highly soluble in water at 50 g/100 mL, yielding strongly acidic solutions.
Though highly toxic to some echinoderms, it is nearly harmless to many other organisms, making it a strategic choice for managing crown-of-thorns starfish outbreaks.
Other Information on Sodium Bisulfate
1. Manufacturing Process of Sodium Bisulfate
Anhydrous sodium bisulfate is produced by reacting concentrated sulfuric acid with sodium chloride and applying heat until melting occurs.
NaOH + H2SO4 → NaHSO4 + H2O
The monohydrate form results from the reaction of concentrated sulfuric acid with an aqueous solution of sodium sulfate.
Na2SO4 + 2H2O + H2SO4 → 2NaHSO4·H2O
Sodium bisulfate is industrially synthesized as an intermediate in the Mannheim process, through the reaction of sodium chloride with sulfuric acid.
NaCl + H2SO4 → HCl + NaHSO4
2. Reaction of Sodium Bisulfate
Above 300°C, sodium bisulfate dehydrates, forming sodium pyrosulfate, which further decomposes into sodium sulfate and releases SO3 upon heating.
2NaHSO4 → Na2S2O7 + H2O
Na2S2O7 → Na2SO4 + SO3
3. Regulatory Information
While sodium bisulfate is not covered by major safety regulations, it is classified as a corrosive substance, necessitating careful handling.
4. Handling and Storage Precautions
Recommended handling and storage precautions include:
- Storing in a tightly sealed container, in a cool, dark place away from direct sunlight.
- Using glass or plastic containers to prevent reaction with metals.
- Operating only in outdoor or well-ventilated areas.
- Exercising caution when heated due to the release of toxic fumes.
- Avoiding unnecessary mixing with alcohol or water to prevent reactions.
- Being cautious of its reaction with many metals, which can generate flammable and explosive hydrogen gas.
- Wearing protective gloves, eyewear, and clothing during use.
- Washing hands thoroughly after handling.
- Washing with soap and water in case of skin contact, and rinsing eyes cautiously with water for several minutes in case of eye contact.