Glossary · Chemistry
Campden tablet
Also written Campden, metabisulphite tablet. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
A pressed tablet of sodium or potassium metabisulphite supplying a standard small dose of sulphur dioxide, sized for domestic and small-scale batches.
- Subject
- Chemistry
- Also written
- Campden, metabisulphite tablet
In more detail
One tablet is conventionally taken to give about 50 mg/L of sulphur dioxide in a gallon, or roughly 8 to 10 mg/L in a litre-scale calculation, depending on the tablet. The name comes from the Campden research station where fruit preservation work standardised the dose; it is a trade term, not a chemical one.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Fermentation
Sulphiting
Adding sulphur dioxide, usually as potassium or sodium metabisulphite, to juice or cider to suppress spoilage organisms, inhibit oxidation and enzymatic browning, and give a selected yeast a clear field.
Chemistry
Sulphur dioxide
The antimicrobial and antioxidant additive of cider and wine-making, added as a metabisulphite salt or as gas. In solution it exists as molecular SO₂, bisulphite and sulphite, in proportions set by pH.
Chemistry
Free sulphur dioxide
The portion of added sulphite still in equilibrium in solution as molecular SO₂, bisulphite and sulphite ions, and therefore still available to protect the cider.
Where to go next
- Cider glossary — The whole vocabulary, by subject and A–Z.
- Comparisons — Terms that are only really clear when set against the thing they are not.
- Search — Finds terms by their aliases and by their spellings in other languages.
Sources
What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.
The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers
Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25
Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.
The Science of Cidermaking and associated technical writing
Andrew Lea · reference work · passage verified 2026-08-24
Written by a food chemist who worked at Long Ashton on apple phenolics. Unusual among specialist cider writing in that it is primary-research-adjacent: the author is describing work he did, and cites the literature. This is why it is registered at tier 1 for chemistry while a general cider book is not.