ASTM D3228 Test Method for Total Nitrogen In Lubricating Oils and Fuel Oils By Modified Kjeldahl Method
3. Summary of Test Method
3.1 The sample is digested in a mixture of concentrated sulfuric acid, potassium sulfate, mercuric oxide, and copper sulfate. After digestion, sodium sulfide is added to precipitate the mercury, and the mixture is made alkaline with caustic. Nitrogen, now in the form of ammonia, is distilled into a boric acid solution. The ammonia is titrated with standard sulfuric acid using methyl purple as an indicator.
4. Significance and Use
4.1 The concentration of nitrogen is a measure of the presence of nitrogen-containing additives. Knowledge of its concentration can be used to predict performance.
