The chemical interaction between ammonium polyphosphate (APP) and talc was studied under dynamic or isothermal heating conditions. The products of interaction were identified by X-ray methods or separated by thin layer chromatography and analysed. It was shown that APP decomposes above 280-degrees-C and starts to interact with talc above 300-degrees-C, giving binary ammonium silicon tetrapolyphosphate and ammonium magnesium polyphosphate or cyclophosphate depending on the initial APP/talc ratio in the mixture. The formation of magnesium cyclotetraphosphate, magnesium ultraphosphate, silicon oxymonophosphate and silicon diphosphate is observed after further heating at 400-800-degrees-C. A glass of magnesium silicon phosphate is formed at 1000-degrees-C. The schemes of chemical reactions occurring at different temperatures are proposed for various APP/talc ratios.