Thermodynamic functions, selected substance

Characteristics of a series of these works are (l)the thermodynamic functions were determined by direct microcalorimetric measurements at (2) merely one fixed temperature, (3)on the systems CD +ROH +H2O which contained no other substance except the surface of purified metallic mercury, and (4)the systems were selected systematically. 

Metallurgical, materials, ceramic and chemical engineers worldwide will welcome this new compilation of thermochemical data by Professor Barin. Here they will find the most comprehensive tables yet available for the thermodynamic properties of pure substances as a function of temperature at 100° intervals. Almost twenty-four hundred substances are included - the elements, and compounds of two, three, and four elements. The vast majority of substances are inorganic, but Dr. Barin has included a generous selection of the more common hydrocarbons, carbohydrates, and a few chlorinated hydrocarbons. The format of the tables conforms to that of the JANAF tables, and SI units are employed. 

Data values were extracted from the SOURCE database by suitable software and then screened to identify the "best" (most accurate) values. The selection was based on a comparison of the estimated uncertainties of values for the same substance. The selection also took into account the distribution of virial coefficients with temperature. An appropriate algorithm has been developed at the Thermodynamics Research Center and has been used for several compilations. Briefly, the uncertainty for each data valne in a set was compared to a weighted mean of the uncertainties of all the other values. The weighting factor was an inverse exponential function of the absolute value of the difference between the temperature of the value being evaluated and the temperatures of the other values. The screeiung level, the size of the data set and range of temperatures it covered determined the parameters used in the comparison. Additional details are given in [96-wil/mar]. Selected values are marked with various symbol in the tables of data. 

Equations of state are used in engineering to predict the thermodynamic properties in particular the phase behaviour of pure substances and mixtures. However, since there is neither an exact statistical-mechanical solution relating the properties of dense fluids to their intermolecular potentials, nor detailed information available on intermolecular potential functions, all equations of state are, at least partially, empirical in nature. The equations of state in common use within both industry and academia are described elsewhere in this book and can be arbitrarily classified as follows (1), cubic equations derived from the observation of van der Waals that are described in Chapter 4 (2), those based on the virial equation discussed in Chapter 3 (3), equations based on general results obtained from statistical mechanics and computer simulations mentioned in Chapter 8 and (4), those obtained by selecting, based on statistical means, terms that best represent the available measurements obtained from a broad range of experiments as outlined in Chapter 12. The methods used for mixtures are also alluded to in these chapters and in Chapter 6. 

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