Thermodynamics thermometry

Critical Data in Physics and Chemistry Thermodynamics Thermometry Water Conditioning,... 

Most thermometry using the KTTS direcdy requites a thermodynamic instmment for interpolation. The vapor pressure of an ideal gas is a thermodynamic function, and a common device for reali2ing the KTTS is the helium gas thermometer. The transfer function of this thermometer may be chosen as the change in pressure with change in temperature at constant volume, or the change in volume with change in temperature at constant pressure. It is easier to measure pressure accurately than volume thus, constant volume gas thermometry is the usual choice (see Pressure measurement). 

The KTTS depends upon an absolute 2ero and one fixed point through which a straight line is projected. Because they are not ideally linear, practicable interpolation thermometers require additional fixed points to describe their individual characteristics. Thus a suitable number of fixed points, ie, temperatures at which pure substances in nature can exist in two- or three-phase equiUbrium, together with specification of an interpolation instmment and appropriate algorithms, define a temperature scale. The temperature values of the fixed points are assigned values based on adjustments of data obtained by thermodynamic measurements such as gas thermometry. 

Thermochemistry, 254, 507 Thermodynamic potentials, 99 Thermo-electric circuit, 450 inversion, 451 theories, 453 Thermometers, 3, 140, 166 Thermometry, 1, 353 Thomsen-Berthelot principle, 257, 506... 

The ITS-90 scale is designed to give temperatures T90 that do not differ from the Kelvin Thermodynamic Scale by more than the uncertainties associated with the measurement of the fixed points on the date of adoption of ITS-90 (January 1, 1990), to extend the low-temperature range previously covered by EPT-76, and to replace the high-temperature thermocouple measurements of IPTS-68 with platinum resistance thermometry. The result is a scale that has better agreement with thermodynamic temperatures, and much better continuity, reproducibility, and accuracy than all previous international scales. 

Consultative Committee for Thermometry creation of a mise en pratique of die definition of the kelvin The Consultative Committee for Thermometry, considering that the ITS-90 and the PLTS-2000 are internationally accepted practical temperature scales defining temperatures T90 and T2qqq that are good approximations to thermodynamic temperature T... 

The ITS is an artifact scale, designed to relate temperature measurements made with practicable instruments as closely as possible to the thermodynamic scale. The scale is established and controlled by the International Committee of Weights and Measures (BIPM) through its Consultative Committee on Thermometry, which was established in 1937. The BIPM itself is established to maintain and implement the Treaty of the Meter, to which most nations of the wodd subscribe thus the ITS has not only scientific but legal status in most nations. Within nations, the Temperature Scale is maintained by national standards establishments, eg, in the United States the National Institute for Standards and Technology (NIST), in England the National Physical Laboratory (NPL), and in Germany the Physikalisch-Technische Bundesanstalt (PTB). 

Practical measurements of temperature long preceded the theory of this important concept. Thermodynamics clearly requires the temperature concept, but thermometry (the theory of temperature measurements) is so deeply intertwined with general thermodynamic theory that we must take care to avoid logical circularity. 

A temperature of 0 K is called absolute zero . It coincides with the minimum molecular activity, i.e., thermal energy of matter. The thermodynamic temperature was formerly called absolute temperature . In practice, the International Temperature Scale of 1990 (ITS-90) [i] serves as the basis for high-accuracy temperature measurements. Up to 700 K, the most accurate measurements of thermodynamic temperature are the NBS/NIST results for Constant Volume Gas Thermometry (CVGT). Above 700 K, spectral radiometry is used to measure the ratio of radiances from a reference... 

In the preceding discussion we identified temperature levelsby the kelvin scale, established with ideal-gas thermometry. This does not preclude taking advantage of the opportunity provided by the Camot engine to establish a thermodynamic tempQxaXnxe scale that is traly independent... 

Precision thermometry based on the thermodynamic temperature scale had its beginnings with the work of P. Chappuis and of H. L. Callendar during the period from the late 1880s to the early 1900s. Chappuis transferred the hydrogen scale in the range from 0 to 100°C, provided by his constant-volume hydrogen gas thermometer, to several carefully made mercury thermometers (Chappuis, 1888). These were then used to calibrate many other mercury thermometers which in turn were to be used in many countries to put temperature measurements on the same scale. The probable uncertainty of those thermometers was stated to be 0.002°C. 

Guildner, L. A. (1980), Accuracy of Realizing Thermodynamic Temperatures by Gas Thermometry, PTB-Mitteilungen 90, 41. 

From the zeroth law of thermodynamics, we know that two systems that are in thermal equilibrium with a third system are in thermal equilibrium with one another and, by definition, have the same temperature. The zeroth law is not only important in defining systems that have the same temperature, but it also provides the basic principle behind thermometry one measures temperatures of different systems by thermometers that are, in turn, compared to some standard temperature systems or standard thermometers. 

Introduction. Historically, low-pressure, constant-volume gas thermometers were the only primary thermometers that had the accuracy required for determining the temperatures of defining fixed points. Recent advances in thermometry have resulted in the development of several types of primary thermometers capable of accurate thermodynamic temperature measurements [5-6]. A list of present-day primary thermometers capable of thermodynamic temperature measurement includes ... 

Clayton RN (1981) Isotopic thermometry. In Newton RC, Navrotsky A, Wood BJ (eds) The Thermodynamics of Minerals and Melts. Springer-Verlag, Berlin, p 85-109. 

More fundamental is the thermodynamic temperature scale. It is based on the second law of thermodynamics which is discussed in Sect. 2.2. This temperature scale is defined such, to be identical to the gas temperature in the region where the gas temperature is measurable. The thermodynamic temperature scale is independent not only of any material property, but also of the state of matter. The zero of the thermodynamic temperature fixes the zero of thermal motion. For more details on thermometry, see Sect. 4.1. 

Thermodynamics provides the framework of functions of state. All our experimental experience can be distilled into the three laws of thermodynamics (or four, if one counts the zeroth law, mentioned in the discussion of thermometry in Sect. 4.1). Not so precisely, these three laws have been characterized as follows [6] In the heat-to-work-conversion game the first law says you cannot win, the best you... 

To describe the thermodynamic equilibrium behavior at the transition, one can write the boxed equations in Fig. 2.119. Inspection of these equations shows that thermometry, discussed in Sect. 4.1, can give a characterization of a material if there is information on either the heats or entropies of transition. Some help for interpretation comes from the fact that related materials have similar changes in disorder—the entropies of transition are similar for structurally related materials. 

The most common method of temperature measurement is contact thermometry, as demonstfated in Fig. 4.1. One brings a thermometer, C, a system with a known thermal property, into intimate contact with the to be measured system, A. Next, thermal equilibration is awaited. When reached, the temperatures of A and C are equal. The use of C as a contact thermometer is based on the fact that if the two systems A and B are in thermal equilibrium with C they must also be in thermal equilibrium with each other. This statement is sometimes called the zeroth law of thermodynamics. It permits to use B with a known temperature to calibrate C, and then use C for measurement of the temperature of system A. A calibration with B can be made at a fixed temperature of a phase transition without degree of freedom, as given by the phase rule of Sect. 2.5.7. Less common are methods of temperature measurement without a separate thermometer system. They make use of the sample itself. For example, the temperature of the sample can be determined from its length, the speed of sound within the sample, or the frequency of light emitted. 

Temperature and thermometry are of fundamental importance in thermodynamics. Unlike the other physical quantities discussed in this chapter, temperature does not have a single unique definition. The chosen definition, whatever it may be, requires a temperature scale described by an operational method of measuring temperature values. For the scale to be useful, the values should increase monotonically with the increase of what we experience physiologically as the degree of hotness. We can define a satisfactory scale with any measuring method that satisfies this requirement. The values on a particular temperature scale correspond to a particular physical quantity and a particular temperature unit. 

Thermometry is based on the principle that the temperatures of different bodies may be compared with a thermometer. For example, if you find by separate measurements with your thermometer that two bodies give the same reading, you know that within experimental error both have the same temperature. The significance of two bodies having the same temperature (on any scale) is that if they are placed in thermal contact with one another, they will prove to be in thermal equilibrium with one another as evidenced by the absence of any changes in their properties. This principle is sometimes called the zeroth law of thermodynamics, and was first stated as follows by J. C. Maxwell (1872) Bodies whose temperatures are equal to that of the same body have themselves equal temperatures. ... 

Two particular temperature scales are used extensively. The ideal-gas temperature scale is defined by gas thermometry measurements, as described on page 42. The thermodynamic temperature scale is defined by the behavior of a theoretical Carnot engine, as explained in Sec. 4.3.4. These temperature scales correspond to the physical quantities called ideal-gas temperature and thermodynamic temperature, respectively. Although the two scales have different definitions, the two temperatures turn out (Sec. 4.3.4) to be proportional to one another. Their values become identical when the same unit of temperature is used for both. Thus, the kelvin is defined by specifying that a system containing the solid, liquid, and gaseous phases of H2O coexisting at equilibrium with one another (the triple point of water) has a thermodynamic temperature of exactly 273.16 kelvins. We... 

Fermi, E. 1956. Thermodynamics. New York Dover. Based on lectures given by Fermi in 1936, this book is about pure thermodynamics. Fermi describes the state of a system and its transformations, the first and second laws of thermodynamics, thermodynamic potentials, and thermodynamics of dilnte solntions. This is an elanentary treatment of thermodynamics, but the reader should be familiar with the fundamentals of thermometry and calorimetry. 

With this link between the microscopic and macroscopic description of matter securely established, the next chapter of the book will concentrate on the description of the various theories needed for the understanding of thermal analysis, namely equilibrium and irreversible thermodynamics and kinetics. The Introduction will then be completed with a summary of the specific functions needed for the six basic branches of thermal analysis thermometry, differential thermal analysis, calorimetry, thermomechanical analysis, dilatometiy, and thermogravimetiy. 

The most basic thermal analysis technique is simple thermometry. The functions of state needed for thermometry are temperature and time. Temperature was discussed already to some degree as the fundamental variable of state for all thermal analysis in Figs. 1.1-1.4. At this point one must add a concise temperature definition that is now, after the review of thermodynamics, easily understood Temperature is the partial differential of total energy U with respect to entropy at constant composition and volume. This definition is written as Eq. (1) of Fig. 2.13 and can easily be derived from Eqs. (1) and (3) of Figs. 2.2 and 2.3. At constant composition and volume no work (i.e. volume work) can be done, so that dw must be zero. In this case... 

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