Sealed-Tube Dissolution Method for Determination of Nitride Nitrogen in Boron Carbide

摘要

Nitride nitrogen in B4C is determined by dissolving the sample in 14M H2SO4 in a sealed fused-silica tube, distilling the nitrogen as ammonia from alkaline solution, and titrating the ammonium hydroxide in the distillation receiver with standardized acid. The Winkler distillation and the titration are proven operations that are directly applicable to the analysis of the B4C solution. Recovery of nitrogen from B4C was difficult and time-consuming by the usual caustic-fusion and leach methods, but it was simplified by substituting the technique of high-temperature dissolution in 14M H2SO4 With the sealed-tube method, analysis of six prepared mixtures of BN and B4C gave a mean recovery of 99.9％ nitrogen, with a standard deviation of 0.94％. Fourteen portions of B4C production material gave a mean nitrogen value of 917 ppm, with a standard deviation of ± 30 ppm. Twelve analyses of the same material by the caustic-fusion method gave a mean nitrogen content of 928 ppm, with a standard deviation of ± 84 ppm. The sealed-tube method for determining nitrogen is highly selective;none of the impurities found in B4C interfere.