<p> An investigation has been made concerning the solubility of nitrogen in pure liquid iron, iron-carbon and ironaluminium alloys. A technique involving levitation melting and a rapid quench device has been used. The experimental data obtained have been expressed in terms of the interaction coefficients proposed by Wagner and Lupis and Elliott. The data have also been used to test the formalisms developed recently by Darken and Chipman. A simple model for liquid metal solutions in which the solutes may be considered "interstitial" has been developed and tested using the results of the present study and published data for a number of ternary solutions </p> / Thesis / Doctor of Philosophy (PhD)