Louis-Bernard Guyton de Morveau,
John Frederic Daniell
thermometry
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Platinum pyrometer
- Louis-Bernard Guyton de Morveau
- realized that thermal expansion of a metal
- could provide an alternative to Wedgwood’s
- method of determining high temperatures,
- and Guyton had worked with platinum for years.
- He placed a bar of platinum in a small ceramic trough
- open at one end and closed on the other,
- and he fixed this on a platinum plate
- so that the platinum bar pressed the short arm
- of a small platinum lever whose longer arm
- moved across a scaled platinum arc.
- *
- Guyton calibrated his platinum pyrometer
- with a mercury thermometer at low temperatures
- and compared Wedgwood’s pyrometer
- at higher temperatures. Although he showed
- that Wedgwood’s readings were too high,
- he concluded that Wedgwood’s pyrometer
- was more practical. Guyton’s delicate
- platinum spring and lever likely bent and fused
- at temperatures above the melting point of antimony.
- *
- In 1830, John Frederic Daniell improved
- Guyton’s pyrometer by separating the heated parts,
- placing the expanding bar in a cylinder of graphite.
- After removing these from immersion in molten metals,
- he clipped a lever and dial on them to measure
- the thermal expansion of the bar.
Daniell’s Register-Pyrometer
- On a new Register-Pyrometer,
- for measuring the Expansions of Solids,
- and determining the higher Degrees
- of Temperature upon the common
- thermometric scale
- by J. Frederic Daniell, Esq., F.R.S.
Practical problems
- The main trouble was the darned metal got soft.
- Also, like Wedgwood’s scale, it could be calibrated
- only at low temperatures. Well,
- practical problems typically accompany any attempt
- to venture into an unexplored space.
- One reason for ignorance—it ain’t easy, even though
- the promise of knowledge leads many to risk failure.
Guyton’s pyrometer was essentially the same as Ferguson’s; however, whereas Ferguson intended his to measure the relative thermal expansions of different metals, Guyton intended his to measure absolute temperatures.
See also in The book of science:
Readings in wikipedia:
Other readings: