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1. On a Practical Constant-Volume Air Thermometer

Published online by Cambridge University Press:  15 September 2014

J. T. Bottomley
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Extract

In the fourth Mémoire of his celebrated Relation des Expériences, published in 1847, Regnault gives cogent reasons for preferring the air thermometer before any other as the instrument by means of which temperatures may be defined, and high temperatures determined. The thermodynamic researches of Sir William Thomson have furnished an absolute thermodynamic definition of temperatures ; and the experimental researches of Dr Joule and Sir William Thomson have established the practical agreement of Regnault's air thermometers with the thermodynamic scale of temperatures. Lastly, the air thermometer is at present the only instrument, with the exception of a mercurial thermometer which has been compared with an air thermometer, by means of which temperatures higher than, say, 150° C. or 200° C. can be determined within 3° C. or 4° C.*

Type
Proceedings 1887-88
Information
Proceedings of the Royal Society of Edinburgh , Volume 15 , 1889 , pp. 85 - 93
Copyright
Copyright © Royal Society of Edinburgh 1889

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References

note * page 85 Mr H. L. Callendar has proposed to use the resistance of platinum for thermometric purposes ; but in this case also the final standard of reference is the air thermometer

note * page 91 By this process every trace of moisture and condensed air is driven up from the walls of the tube; and, the bulb being filled with perfectly dry air, it seems certain, from the experiments of Bunsen and from experiments which I have myself carried out, that there is no subsequent perceptible condensation of air at the surface of the glass, such as has sometimes been supposed to vitiate the readings of the air thermometer. Air only condenses on the surface of the glass when there is moisture present—at any rate in such quantity as would be perceptible in a case like the present.