The tutorial discusses electrochemical methods for studying chemical reactions in molten salts, namely: metal-salt reactions, disproportionation, catalytic self-dissolution, competing complexation, polymerization and clustering. Methods for preventing the occurrence of chemical reactions that complicate the electrolysis process are considered. The results of the synthesis of functional materials using chemical reactions and their influence on the processes of electrolytic production of refractory metals are presented. The book is intended for graduate students, reseaches and specialists in the field of high temperatures physical chemistry and electrochemistry, the production of rare refractory metals and the creation of new fuctional materials.