in Chemistry M.P. Semenenko Institute of geochemistry, mineralogy and ore formation of the National Academy of sciences of Ukraine B.S. Homenko, senior engineer Institute of General and Inorganic Chemistry By methods of pH monitoring of filtration solutions as well as due to determination of residual concentrations of ions Мg 2+ and РО 4 3the bishofite-phosphate acid interaction was studied with the given ratio [РО 4 3-]:[Мg 2+ ] = 0,187-5,24. The precipitation arising from the reaction was studied by chemical, thermal gravimetric and X-ray phase analysis and its compliance with the formula xNH 4 MgPO 4 • yMgHPO 4 was established, where х = 0,25; у = 0,75. UDC546.41.185 ________________________ *Supervisorofstudies-professorO.P.Perepelytsya.