Abstract
In order to elucidate the optimum conditions for the determination of nitrogen in coke, each of the semi-micro Kjeldahl, semi-micro gasification and automatic Duma's methods was investigated in some detail, and the following results were obtained.
(1) In the case of the semi-micro Kjeldahl method, the catalyst including selenium hastened remarkably the decomposition of coke in comparison with the catalyst excluding selenium, but the excessivey elongated heating after the termination of decompositions made the analytical results decreased. It was also recognized that the digestion time was affected by the degree of graphitization and particle size of the sample.
(2) In the case of semi-micro gasification method, although the procedure under the condition of the current JIS method gives preferable results, the precision of the analytical results was more improved by pulverizing the coke sample up to 74μm and adding soda lime in 20-25 times as much as the sample. This method has possessed so many merits in comparison with other methods as the good precision in the analytical results, the unnecessity of toxious reagents and the simplicity and rapidity in the procedure.
(3) In the case of automatic Duma's method, the reason why higher values in the analytical results were turned out in comparison with the former two methods was conjectured to be attributed to the generation of inert gases, and these bias could be improved considerably by pulverizing the samle to under 38μm, purging air at 100-300°C, and adjusting the combustion temperature to 1000-1100°C.
The reanalyses about the sample used in previous paper were carried out by adopting the improved conditions based on the above conclusions. The bias among the three types method mentioned above could be diminished until insignificant level.
