ASTM D1318 Test Method for Sodium in Residual Fuel Oil (Flame Photometric Method)
5. Apparatus
5.1 Flame Photometer, capable of isolating the sodium doublet at 589 nm and stable enough to give repeatable measurements that do not vary more than 5 % of their mean in the 2 to 20 mg/kg range of sodium.
5.2 Platinum Dish, 100-mL capacity, approximately 35 mm in depth.
5.3 Electric Muffle Furnace, capable of operating over a variable range from 200 to 600°C and of maintaining a temperature of 550 more or less 50°C.
6. Reagents and Materials
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 can 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 Type II or III of Specification D1193.
6.3 Hydrochloric Acid (sp gr 1.19) - Concentrated hydrochloric acid (HCl). (Warning - Poison. Causes severe burns. Harmful or fatal if swallowed or inhaled.)
6.4 Hydrochloric Acid (1+9) - Mix 1 volume of HCl (sp gr 1.19) with 9 volumes of water.
6.5 Hydrofluoric Acid (48 %) - Concentrated hydrofluoric acid (HF). (Warning - Poison. Causes severe burns. Harmful or fatal if swallowed or inhaled.)
6.6 Sodium Solution, Standard (1000 mg Na/L) - Dissolve 3.088 more or less 0.005 g of dried sodium sulfate (Na2SO4) in water and dilute to 1 L in a volumetric flask. Store in a polyethylene bottle.
6.7 Sulfuric Acid (1+1) - Carefully add, while stirring, 1 volume of concentrated sulfuric acid (H2SO4, sp gr 1.84) to 1 volume of water. (Warning - Poison. Causes severe burns. Harmful or fatal if swallowed or inhaled.)
7. Sampling
7.1 Sampling shall be done in accordance with Practices D4057 or Test Method D4177.
7.2 Use a clear, clean glass pint bottle, previously rinsed twice with HCl (1+9) and once with water and allowed to dry, for sampling the bulk material or plant streams. Obtain a representative sample but do not fill the bottle more than about two-thirds full. Warm viscous samples until they can be mixed readily. Stir up any material that has settled out and shake the sample for 3 min just prior to weighing it out.
7.3 Optimum sample size for most instruments is that which contains from 0.5 to 1.0 mg of sodium. Estimate the sample size as follows (see Note 1):
Sample size, g = 750/estimated sodium content, mg/kg
NOTE 1 - An estimate of the maximum amount of sodium in a sample can be obtained from its ash value. For example, an ash of 0.01 % would undoubtedly have less than 0.005 % sodium (50 ppm). If there is no estimate as to the probable sodium range in a sample, it is more expedient to weigh out a large amount, for example 60 g, because the test method provides for dilution of sample solutions that are more concentrated than the standards.
