Background Sketch to the Problem

I can do all things through Christ. With that firm belief, I give God who enabled me to start and complete this research all the glory. My sincere thanks for the guidance of:- My supervisor, Prof. M.K. Du Toit, for his guidance and support.- My husband Clinton for his loyal support and encouragement. In memory of my father, Hermanus, who believed that "If you can dream it, you can achieve it". My mothers, Muriel and Salome, from whom I learned the strength to perservere and complete my research against all odds.- The financial assistance of Billiton South Africa. 4CONTENT