Bestimmung von stickstoff in refraktärmetallen—II Titan

This is a report on round-robin tests concerning the determination of nitrogen in titanium, which were carried out by the refractory-metals group of the chemical board of the Gesellschaft Deutscher Metallhütten- und Bergleute. The following methods were used: classical and modified Kjeldahl methods, inert gas fusion and vacuum fusion extraction. With the platinum (or palladium) flux technique (noble metal to sample ratio ～ 20 : 1, temperature ? 2000°) the reductive fusion methods are capable of determining nitrogen contents ? 20 ppm. Under special conditions, contents higher than 10–40 ppm can be determined by the Kjeldahl method (the lower limit varies from laboratory to laboratory). With a micro circulating distillation and determination apparatus, and dissolution of the sample within the pressure vessel, the detection limit can be lowered to 1 ppm. Because of possible interferences by reducible nitrogen compounds from the laboratory air, blanks must be determined with high-purity aluminium. The results from 7 laboratories (Kjeldahl 4; reductive fusion 3) for a titanium sample containing 138 ppm nitrogen were in good agreement (standard deviation 5 ppm).