[en] Developed is the technique for determining large amounts of vanadium(5) and (4) in the case of mutual presence and low oxidation levels in terms of VO₂ in glass of the V₂O₅-CaO-Al₂O₃-SiO₂ system, synthesized under various oxidation-reduction conditions. For this purpose determination oxidation-reduction methods have been used, and conditions for the glass transformation into a soluble form with the retention of vanadium valent states in solutions have been selected. The glass sample decomposition for vanadium (5) and (4) determination has been performed in the carbon dioxide atmosphere in a quartz device with a mixture of sulfuric and hydrofluoric acids. It has been established that the sample solution takes up from 10 to 20 minutes, depending on their synthesis conditions. Presented is a diagram of methematical processing the data, obtained as a result of analysis