Abstract <p>Changes in the composition of aluminum hypophosphite, calcium hypophosphite, and their mixtures with oxidizers after combustion in air under atmospheric pressure have been studied by X-ray photoelectron spectroscopy (XPS). It has been established that the formation of colored condensed combustion products is associated with the formation of the corresponding phosphides. A hypothesis is proposed that the source of phosphide formation is phosphine and its reactive decomposition products generated during the disproportionation reaction of hypophosphites.</p>