What does bisulfate mean?
A bisulfate is a chemical species built around the hydrogen sulfate anion, HSO₄⁻, which forms when sulfuric acid loses just one of its two acidic protons. The term refers both to that ion itself and to any salt or ester containing it — sodium bisulfate (NaHSO₄) and potassium bisulfate (KHSO₄) being the most familiar examples. Because these compounds are mildly acidic yet safe enough to handle, they find everyday work as 'dry acid': sodium bisulfate lowers the pH of swimming pools and is a common ingredient in toilet-bowl cleaners and metal-finishing solutions. In solution, bisulfate sits in equilibrium between fully protonated sulfuric acid and fully deprotonated sulfate, which makes it chemically useful as a buffer and acidifying agent. The word belongs firmly to the vocabulary of chemistry, industry, and pool maintenance rather than casual speech, and in modern systematic nomenclature it is often called 'hydrogen sulfate' instead. Its near-namesake bisulfite, based on sulfurous rather than sulfuric acid, is a frequent source of confusion.
nounA chemical compound or anion containing the group HSO₄⁻; specifically, the salt or ester of sulfuric acid in which only one of its two acidic hydrogens has been replaced.
- The hydrogen sulfate anion, HSO₄⁻, formed by partial deprotonation of sulfuric acid.
- Any salt or ester containing this anion, such as sodium bisulfate (NaHSO₄) or potassium bisulfate (KHSO₄).
"The technician dissolved sodium bisulfate in water to lower the pH of the swimming pool."
"Sodium bisulfate is commonly added to swimming pools to lower the pH without raising calcium hardness."
"In aqueous solution, the bisulfate ion exists in equilibrium with sulfate ions and free protons."
Used when referring collectively to different bisulfate salts, e.g., sodium and potassium bisulfates.
"Several alkali-metal bisulfates are commercially available as dry acids."
That white granular powder sold as 'dry acid' for pools and toilets is usually just sodium bisulfate — sulfuric acid with one hydrogen still attached.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of bisulfate
The word bisulfate combines the prefix 'bi-', here indicating a compound derived from another by replacement of only part of its replaceable atoms, with 'sulfate', itself formed from 'sulfur' plus the '-ate' suffix used for the salts of oxoacids. It arose within the Latin-based nomenclature of early modern chemistry, alongside parallel formations such as 'bisulfite'. Its closest relatives are therefore the other sulfur-oxygen chemical terms: sulfate, sulfite, and sulfuric.
Related word forms
How bisulfate is actually used
The term is used almost exclusively in chemistry and technical contexts and is essentially never heard colloquially. In formal IUPAC nomenclature, 'hydrogen sulfate' is preferred over 'bisulfate', though 'bisulfate' remains widespread in industrial, commercial, and older laboratory usage.
Easily confused with bisulfate
Bisulfites contain the HSO₃⁻ ion derived from sulfurous acid, whereas bisulfates contain the HSO₄⁻ ion derived from sulfuric acid.
A disulfate contains two sulfate groups linked together (S₂O₇²⁻), while a bisulfate contains a single hydrogen sulfate group.