[en] The Federal Bureau of Mines has studied the reaction of oxides of niobium, vanadium, and tantalum with ammonia in vertical, gas-solids reactors at temperatures ranging from 300 to 1,300⁰C with the goal of preparing nitride intermediates for subsequent preparation of the metals by a thermal-decomposition step. Factors which affected the first part of the overall process were investigated in detail to optimize the conditions necessary for conversion of the oxides to the nitrides. These included reactor material, temperature, composition, and space velocity of the nitriding gases, and particle size and thermal treatment of the oxides. The best nitride conversions were obtained in nonmetal reactors of Al₂O₃ or Vycor. With Nb₂O₅, V₂O₃, and V₂O₅, low-temperature maxima in reaction rates occurred at 800, 800, and 450⁰C, respectively, during oxynitride formation (in Al₂O₃) at 1 atm of pure ammonia. Under fully optimized conditions, products containing less than one percent oxygen were readily obtained in under 6 hours