Callendar

Electrical resistance thermometers, the most widely used of which is Callendar s platinum resistance thermometer. This is probably the most convenient and accurate apparatus for measuring temperatures between the boiling-point of liquid air (—190° C.) and the melting-point of platinum (1,500° C.). Lead has recently been applied at very low temperatures. 

Rowland first observed that the value of J varies with the. temperature, and if the mechanical equivalent of the 15° calorie be taken as standard, the ratio of the value of J at any temperature to this gives the specific heat of water at that temperature. He found the curious result that the specific heat of water had a maximum value at about 30° Callendar and Barnes located this at 37° 5. 

Tables 11 A, 1 IB, 11C and 11D are adapted from the Abridged Callendar Steam Tables by permission of Messrs Edward Arnold (Publishers) Ltd.

Powers, S., Byrd, R., Tulley, R., and Callendar, T., Effects of caffeine ingestion on metabolism and performance during graded exercise, European Journal of Applied Physiology, 50, 301, 1983. 

In conclusion, it may be said that van der Waals equations can only provide reasonably accurate representation over limited ranges of variation of the pressure and temperature. For this reason many attempts were made to produce a more satisfactory equation by modifying vanderWaals equations. Such modifications were made by Berthelot (See item b ), Callendar (See item c-2), Clausius (See item C3), Dieterici (See item d2), Hirschfelder et al (See item 113), Keyes (See item ki), Lees (See item I3), and Macleod (See item mi) Accdg to Dunkle (Ref 17), for high temps and moderate pressures which give rise to large values of V so that P55>a/v2, van der Waals equation reduces to Abel s equation (See item ai)... 

C2) Callendar Equation of State. It is one of the modifications of vanderWaals equations, originally developed to represent the behavior of steam at moderate pressure. It was found to. >e applicable to other vapors and to gases ... 

Equations of state (detonation and expin), listing of Abel, Allan, Beattie-Bridgeman, Becker, Becker-Kistiakowsky-Wilson, Benedict-Webb-Rubin, Berthelot, Boltzman, Brinkley-Wilson, Caldirola Paterson, Callendar,... 

The simple equation of Callendar (5) for the second virial coefficient was used. 

In 1821, Sir Humphrey Davy discovered that as temperature changed, the resistance of metals changed as well. By 1887 H.L. Callendar completed studies showing that purified platinum wires exhibited sufficient stability and reproducibility for use as thermometer standards. Further studies brought the Comitd International des Poids et Measures in 1927 to accept the Standard Platinum Resistance Thermometer (SPRT) as a calibration tool for the newly adopted practical temperature scale. 

For these, and other reasons, it would appear that liquid water is more complex than a binary mixture, and the suggestion first hinted at by Callendar,1 and later developed by Bousfield and Lowry,2 namely, that water is a ternary mixture has much to recommend it. According to this theory liquid water contains ice-, water-, and steam-molecules in equilibrium. In other words its composition is represented by the scheme ... 

Note that IPTS-68 and many simpler interpolation schemes still in use, such as the Callendar-van Dusen equation described below, use the ratio R(7)/R(273.15 K) based on the ice point as the reference temperature. 

Callendar-van Dusen Equation. The complexity of the ITS-90 equations, especially for temperatures below 273.16 K, creates an awkward situation. For practical use, the Callendar-van Dusen equation, which was the basis for IPTS-48, is still a very convenient form. This is especially true if one wishes to determine the resistance R of a Pt thermometer digitally under computer control and convert it into a temperature with a reasonably simple algorithm. The general form of the Callendar-van Dusen equation is... 

The typical uncertainties in temperature values based on a four-point Callendar-van Dusen calibration over the range 180 to +260°C vary from (10 - 20) mK over this... 

Another approach is to use a carefully selected standard platinum alloy for which the constants in Eqs. (6) and (8) are well known. In the mid-1980s, the International Electrotechnical Commission (lEC) recommended that ITS-90 be based on the Callendar-van Dusen interpolation formula and proposed constants for a Ft resistor with = 100 O A = 3.90802 X 10 5=-5.802 X 10 C =-4.27350 X 10 (or a = 0.00385, 8 = 1.50701, /3 = 0.111). The platinum wire used in platinum resistance thermometers that conform to this proposed standard is a platinum alloy containing small amounts of several different elements (mostly noble metals) adjusted so as to achieve the required a = 0.00385 K . This alloy is now widely used in Europe and by some American manufacturers of resistance thermometers note, however, that other American firms use a wire for which a = 0.00392 K . In spite of the fact that this lEC proposal was not adopted, the Callendar-van Dusen constants given above are a guide to appropriate values, which can always be checked by calibration. 

For PRT measurements of normal precision, the Callendar-van Dusen interpolation formula, described by Eqs. (6) to (8), is the most practical choice. Once the constants that appear in Eq. (6) or (8) have been determined, there are two ways to proceed in converting Rt readings into temperatures. One can prepare a conversion table of closely spaced T... 

Regnault s apparatus was improved by Chappuis (mercury), Thiesen, Scheel and Diesselborst (water), Callendar and Moss (mercury), and Osborne, McKelvy, and Bearce (ethyl alcohol). Callendar and Moss used six pairs of hot and cold columns each nearly 2 m. in length. 

Sears palculated from. the results of Chappuis, Callendar and Moss/ and. Hariow (the la t two riot being in very good agreement) ... 

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