What does bisulphate mean?
A bisulphate is a chemical salt formed when sulphuric acid is only partially neutralised, leaving one of its two hydrogen atoms intact. This gives the compound its characteristic hydrogen sulphate ion (HSO₄⁻) and makes bisulphates mildly to strongly acidic. The best-known example is sodium bisulphate, a white crystalline solid widely used to lower pH in swimming pools, in metal finishing, in textile dyeing, and as an acidifying agent in some food applications. Potassium bisulphate appears similarly in laboratory and industrial settings. The word is written 'bisulphate' in British English and 'bisulfate' in American English, reflecting the differing spellings of 'sulphur' and 'sulfur'. It is a technical term encountered chiefly in chemistry, manufacturing, and trade contexts rather than casual speech. Understanding it helps clarify labels and safety information, since bisulphate compounds require sensible handling as corrosive acidic materials despite their commonplace uses around the home and garden.
nounA salt or ester of sulphuric acid in which only one of the two acidic hydrogen atoms has been replaced, containing the hydrogen sulphate ion (HSO₄⁻). The term also denotes any of several specific compounds, such as sodium bisulphate.
- Chemistry: a salt or ester containing the hydrogen sulphate ion (HSO₄⁻), formed by partial neutralisation of sulphuric acid.
- Any of various specific compounds so named, especially sodium bisulphate, used as an acidifying agent in cleaning, water treatment, and food processing.
"The chemist dissolved a measure of sodium bisulphate in water to lower the pool's pH."
"Sodium bisulphate is commonly added to swimming pools to reduce alkalinity safely."
"In the dye works, potassium bisulphate served as an acid mordant for fixing the colours."
The plural refers either to multiple crystals or samples of one bisulphate compound, or to several different bisulphate compounds collectively.
"Various bisulphates are employed across industry as inexpensive acidifying agents."
That 'bi-' doesn't mean two sulphates — it means one lonely hydrogen left clinging to the sulphate ion, which is exactly why bisulphate salts are acidic enough to clean pools and cure leather.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of bisulphate
The word combines the prefix 'bi-' (from Latin, here indicating the retention of one acidic hydrogen atom) with 'sulphate', itself formed from 'sulphur' plus the '-ate' suffix used for oxygen-rich anions in chemical nomenclature. 'Sulphur' descends from Latin 'sulphur', a word of ancient pedigree referring to brimstone. As systematic chemistry nomenclature developed in the eighteenth and nineteenth centuries, terms like sulphate, sulphite, and bisulphate emerged to distinguish salts by their degree of oxidation and protonation, with 'bisulphate' denoting the acid salts of sulphuric acid.
Related word forms
How bisulphate is actually used
The spelling 'bisulphate' follows British conventions (with '-ph-'), while American English uses 'bisulfate'. The word belongs to technical register, appearing mainly in chemistry texts, industrial documentation, and product labels rather than everyday conversation.
Easily confused with bisulphate
A sulphate is the fully deprotonated salt containing the SO₄²⁻ ion, whereas a bisulphate contains the singly protonated HSO₄⁻ ion and is still acidic.
A bisulphite derives from sulphurous acid (containing HSO₃⁻), while a bisulphate derives from sulphuric acid (containing HSO₄⁻).