It is frequently necessary to analyze petroleum feed stocks and products for small amounts (less than 0.1%) of combined nitrogen. The conventional macro-Kjeldahl method requires large samples, prolonged acid digestion, and large amounts of reagents. A semimicro-Kjeldahl procedure has been devised to use small samples and to allow the determination of very low concentrations of nitrogen. The oil samples are digested with acid in special Kjeldahl flasks which fit onto an all-glass apparatus for steam distillation of the ammonia. The ammonia is determined by spectrophotometric measurements of the color developed with Nessler's reagent. Nitrogen present as amino, nitro, nitroso, azo, and ring compounds can be determined on an average to *10% over a concentration range of 0.002 to 1.0%.
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