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Which minerals did Joseph Black use in his experiments on fixed air?
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Joseph Black
Joseph Black, detail of an engraving by J. Rogers after a portrait by Sir Henry Raeburn
In his pioneering research on "fixed air" (now known as carbon dioxide), Joseph Black primarily conducted experiments using the following substances:
- Magnesia alba: Known today as magnesium carbonate, this was the focus of his initial thesis work.12
- Chalk: Chemically identified as calcium carbonate, Black used this in his broader experiments to demonstrate that heating it produced "fixed air" and resulted in quicklime (calcium oxide).13
- Potash: Also referred to as potassium carbonate, Black used this substance to show that "fixed air" could be reintroduced to quicklime or magnesia usta (magnesium oxide) to recreate the original carbonate compounds.1
Through these quantitative experiments, Black proved that "fixed air" was a distinct chemical substance rather than atmospheric air in a different state of purity.13