Study
Observations on different kinds of air
Priestley, Joseph
Philosophical Transactions of the Royal Society of London, 1772
A candle burning in a sealed vessel goes out, and a mouse placed in that same air dies — the air has been, in the language of the time, "injured". Priestley put a sprig of mint into such a vessel, left it for some days, and then tested whether a candle would burn and a mouse survive.
- Studied in
- Mentha
- Sample size
- sealed vessels containing candles, mice and mint sprigs
Air that had been made unbreathable by burning or breathing was restored by the presence of a growing plant, so that a candle would again burn in it and a mouse live.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Vegetation restores air injured by combustion and respiration, and plants are therefore essential to the atmosphere animals depend on.
How NatureHQ reads it
The founding experiment of photosynthesis research, performed before oxygen had a name. What Priestley could not know — and what made his results maddeningly irreproducible for others — is that the effect requires light. Ingenhousz found that seven years later, and the difference between them is the whole reason a plant in a dark cupboard does the opposite of what Priestley described.
- Pre-dates the identification of oxygen and any quantitative gas chemistry.
- The light requirement was not recognised, so results were inconsistent and frequently failed to replicate.
- Qualitative throughout; nothing was measured.
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: The Royal SocietyPublished by the Royal Society.
doi.org/10.1098/rstl.1772.0021
This reference was resolved automatically against Crossref on 2026-08-11.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-08-10.