Chapter 10 - Transport properties in high temperature and pressure ionic solutions

Abstract

This chapter is focused on the study of transport properties in aqueous ionic solutions at elevated temperatures and pressures. The transport coefficients are defined in connection with the phenomenological laws that describe the transport of charge, mass or momentum in electrolyte solutions. The chapter summarizes the laws and the main characteristics of the transport parameters, which include electrical conductivity, transport numbers, diffusion, limiting laws, viscosity, and thermal conductivity. The most successful experimental methods and devices used to measure transport properties in high-temperature and -pressure aqueous solutions containing ionic solutes are High-Temperature Electrical Conductivity Cells and Electrochemical Methods. The simplest apparatus to measure the viscosity of electrolyte solutions is the rolling-ball viscometer, consisting of an inner tube, a ball, and an optical detector. The most precise method for measuring the viscosity of corrosive hydrothermal fluids is the oscillating-disk viscometer. The presence of ionic solutes generates new diffusion coefficients and also modifies to some extent the transport properties of water in the solution. This chapter deals mainly with those transport properties that are a direct consequence of the presence of ionic solutes, i.e., electrical conductivity and solute diffusion. The electrical conductivity, and the diffusion of salts and their ionic components are analyzed as a function of temperature and density (pressure) over the entire concentration range, from infinite dilution to very concentrated solutions.