ASTM D3228 Test Method for Total Nitrogen In Lubricating Oils and Fuel Oils By Modified Kjeldahl Method
5. Apparatus
5.1 Buret, 50-mL, graduated in 0.1-mL subdivisions, one for each titrant. Other size burettes may also be used.
5.2 Flask, Erlenmeyer, 300-mL. Other sizes are also acceptable.
5.3 Heater, electrical or gas.
5.4 Kjeldahl Distillation Apparatus.
NOTE 2 - Commercially available semi-automatic Kjeldahl apparatus are acceptable. In such cases manufacturer prescribed sizes of burettes and flasks may be used.
5.5 Kjeldahl Flask, at least 500-mL volume.
6. Reagents
6.1 Purity of Reagents - Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.
6.2 Purity of Water - Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by Types II and III of Specification D1193.
6.3 Boric Acid Solution (40 g/L) - Dissolve 40 g of boric acid (H3BO3) in 1 L of boiling water.
6.4 Catalyst Reagent - For each test carefully weigh and mix 9.9 g of potassium sulfate (K 2SO4), 0.41 g of mercuric oxide (HgO), and 0.08 g of copper sulfate (CuSO4).
6.5 Methyl Purple Indicator Solution - Aqueous solution containing approximately 0.1 % active constituent (not methyl violet). Other appropriate indicator solutions may also be used.
6.6 Sodium Hydroxide Solution (1000 g/L) - Dissolve 1000 g of sodium hydroxide (NaOH) in 1 L of water. (Warning - See Note 2.)
NOTE 3 - Warning: Causes burns. Poison.
6.7 Sodium Sulfide Solution (40 g/L) - Dissolve 40 g of sodium sulfide (Na2S) in warm water 194°F (90°C); cool and dilute to 1 L.
6.8 Sucrose (NIST) - Primary standard grade.
6.9 Sulfuric Acid (rel dens 1.84) - Concentrated sulfuric acid (H2SO4). (Warning - See Note 3.)
NOTE 4 - Warning: Causes severe burns. Strong oxidizer.
6.10 Sulfuric Acid, Standard (0.05 M) - Slowly add 3 mL of concentrated sulfuric acid (H2SO4, rel dens 1.84) to 500 mL of water in a suitable size beaker. Mix the acid and water; allow it to cool and transfer to a 1-L volumetric flask. Dilute to the mark with water; mix well. Standardize sulfuric acid to the nearest 0.0005 mol/L against 0.1 mol/L NaOH solution using phenolphthalein indicator. Standardize the NaOH solution against primary standard grade potassium hydrogen phthalate (HOOCC6H4COOK). Use the procedure outlined in Sections 14 to 19 of Practice E 200.
NOTE 5 - Commercially available pre-standardized H2SO4 and NaOH solutions may be used.
6.11 Sulfuric Acid (0.005 M) - Prepare by ten-fold dilution of the standard 0.05 M sulfuric acid prepared and standardized in 6.10.
7. Sampling
7.1 Take the sample in accordance with the instructions in Practice D4057.
7.2 Ensure that the sample is thoroughly representative of the material to be tested and that the portion of the sample used for test is thoroughly representative of the whole sample.
