Sodium bisulfate

Sodium bisulfate, also known as sodium hydrogen sulfate, is a chemical compound with the molecular formula NaHSO₄. It is a salt composed of sodium ions and bisulfate ions. Sodium bisulfate is an acidic salt, formed by the partial neutralization of sulfuric acid by an equivalent of sodium hydroxide or sodium chloride. It is a white, granular or crystalline solid, highly soluble in water, producing an acidic solution.

Properties

Sodium bisulfate exists in anhydrous (without water) and monohydrate (NaHSO₄·H₂O) forms. The anhydrous form is hygroscopic, meaning it can absorb moisture from the air. It has a melting point of 315 °C (599 °F) and decomposes before boiling. The monohydrate form loses water at temperatures above 58 °C. Sodium bisulfate is a strong acid in aqueous solution, capable of lowering the pH of a solution, making it acidic.

Production

Sodium bisulfate is produced on an industrial scale by two main methods. The first involves the direct reaction of sulfuric acid with sodium chloride:

2 NaCl + H₂SO₄ → 2 NaHSO₄ + HCl↑

The second method is through the reaction of sulfuric acid with sodium hydroxide, which produces sodium bisulfate and water:

H₂SO₄ + NaOH → NaHSO₄ + H₂O

Uses

Sodium bisulfate has a wide range of applications due to its acidic properties. It is commonly used in:

• Metal finishing and cleaning solutions: to clean metal surfaces and remove rust.
• pH regulation: in swimming pools, spas, and water treatment facilities to lower the pH of water.
• Food industry: as a food additive, it serves as a preservative and acidity regulator. It is recognized by the E number E514.
• Pet care: in pet foods to improve palatability and in litter products as a urine acidifier.
• Chemical synthesis: as a reagent in the synthesis of various chemical compounds.

Health and Safety

Exposure to sodium bisulfate can cause irritation to the skin, eyes, and respiratory system. It should be handled with care, using appropriate personal protective equipment. Ingestion of large amounts can be harmful, leading to symptoms such as nausea, vomiting, and diarrhea.

Environmental Impact

Sodium bisulfate is considered environmentally safe when used and disposed of properly. It is biodegradable and does not accumulate in the environment. However, its acidic nature means it should be neutralized before disposal into the environment to prevent potential harm to aquatic life.