A study of the rate of dissolution of magnesium in acids

Abstract

A brief critical account is given of Nernst's theory of heterogeneous reactions and of the modifications to it that have been proposed by various investigators. This is followed by a summary of the work done by a number of workers with ultrasound in the study of heterogeneous chemical and electrochemical reactions between solids and liquids. In Section II, an account is given of the experimental techniques used in the present work and of the methods of expressing the results. The experimental work carried out by the present author on the reaction between magnesium and hydrochloric acid, and between magnesium and a number of other acids, is described and detailed results reported. Section III is devoted to discussions of methods of effecting a change of control in heterogeneous reactions, to considerations of problems involved in determining chemical rate constants for partly diffusion controlled heterogeneous reactions, and to the mathematical treatment of rate equations for reactions where the apparent area of a dissolving magnesium cylinder changes appreciably during the course of reaction. In Section IV, the experimental results are discussed in detail, and it is shown that the data for the acids investigated in this work do not fit a Br?nsted-Pedersen relationship. Possible reasons for this are examined in detail. Finally, some interesting theories of heterogeneous reactions between solids and liquid reagents are briefly discussed.