Physical, Thermodynamic and Solubility Data

Abstract

This chapter will attempt to present some of the basic physical and ther-modynamic data for potassium chloride and its simple aqueous solutions. However, only a limited amount of data will be given for other potash salts and solutions because of the immense amount of information that would be required to cover all of the potassium compounds and their mixtures. Since potassium chloride is such a common and basic compound it has been extensively studied, and data is available from the late 1800's to the present. In some respects this is a mixed blessing since the data in many cases is inconsistent. The early data was often presented as tables in centigrade and weight percent units, later it was reported in molar (moles/liter) concentrations , but now it is almost always expressed as molal (moles/l ,000 g water) solutions with quite limited and random molal and temperature values for each series of tests. This is the result of the present fairly universal objective of using the data to form very large polynomial equations, and present them instead of the more useable tables of data. The new polynomial equations are then compared to previous researcher's polynomials, but unfortunately discrepancies of 4-20% for some of the data is either ignored or brushed-off as the new values being better than the old ones. With the advent of easy computer fitting of data into equations, and the wide acceptance of Pitzer-type very large polynomials to semi-theoretically correlate and extrapolate thermodynamic properties, this type of data presentation has become dominant for all physical properties. Most authors first develop com