Methods for calculating and predicting nonvariant compositions in two-component systems and methods for analytical description of properties of elements, simple substances, compounds and mixtures of element halides are given. The relationship of elements and simple substances, simple substances and compounds, compounds and mixtures is also shown. It is recommended for students, master's students of the direction of the 04.03.02 "Chemistry, Physics and Mechanics of Materials" (profile "Functional Structural Materials and Nanomaterials"), graduate students of the direction of the 04.06.01 "Chemical Sciences" (profiles "Inorganic Chemistry," "Physical Chemistry"), as well as teachers and employees working in the field of materials science.