Sodium bisulfate (sodium hydrogen sulfate)

Properties and composition

Chemically, sodium bisulfate contains sodium cations and bisulfate anions; the latter are sometimes written HSO4−. The substance is acidic because the bisulfate ion can donate a proton to water. It should not be confused with bisulfite or with the fully neutralized sulfate salt: compare it to sodium sulfate or to sulfite salts. Mention of the separate components is often useful: sodium and the bisulfate ion.

Production and chemical reactions

Industrially and in the laboratory sodium bisulfate is made by partially neutralizing sulfuric acid with sodium hydroxide in controlled amounts; using excess base leads instead to sodium sulfate. This partial neutralization is often described as reaction between sodium hydroxide and sulfuric acid. Another route is heating common salt with sulfuric acid, which yields sodium bisulfate and gaseous hydrogen chloride: a simplified representation is NaCl + H2SO4 → NaHSO4 + HCl; further heating can produce other sulfate products.

Uses and applications

• pH adjustment: a common dry acid for lowering pH in swimming pools, spas, and some industrial water treatments.
• Household and cleaning products: used in some powdered cleaners where an acidic component is required without handling liquid acid.
• Textiles and dyeing: as an acidifying agent during certain dyeing or textile processes.
• Manufacturing: serves as an intermediate or reagent in chemical manufacture where controlled acidity is helpful.

Safety, handling and distinctions

Sodium bisulfate is corrosive to some materials and can irritate skin, eyes, and respiratory tracts if dust is inhaled; it should be handled with appropriate personal protection and stored dry. It is generally safer to ship and use than concentrated mineral acids but still treated as an acidifying chemical. Important distinctions: do not confuse bisulfate (HSO4−) with bisulfite (HSO3−) and note that reaction stoichiometry determines whether sodium sulfate or sodium bisulfate is formed.

For related chemicals and more detailed technical data, consult supplier datasheets and safety literature; further reading on the acid/base behavior and uses is available via general chemical references such as resources about sulfuric acid, sodium hydroxide, and the gaseous byproduct hydrogen chloride. Additional links: sodium, bisulfate ion, sodium sulfate.