ASTM D1121 method for Reserve Alkalinity of Engine Coolants and Antirusts
6. Apparatus
6.1 The pH meter, glass electrode, and calomel electrode, shall be as specified in the section on Apparatus (Section 5) of Test Method D1287.
6.2 It is recognized that many laboratories use a combination electrode system for measuring the reserve alkalinity of engine coolants. It should be noted that results obtained from using a combination electrode system have been found to be statistically different from results obtained when using the calomel and reference electrode system.
7. Reagents
7.1 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.
7.2 Purity of Water - References to water shall be understood to mean distilled water or water of equal purity. Distilled water shall be boiled thoroughly, or purged with carbon dioxide-free air, to remove carbon dioxide, and shall be protected with a soda-lime tube or the equivalent while cooling and in storage. The pH of the water shall be between 6.2 and 7.2 at 25°C. Take precautions to prevent contamination of the distilled water with traces of the material used for protection against carbon dioxide.
7.3 Standard Buffer Solution - The buffer solutions for checking pH assemblies and glass electrodes shall be stored in bottles of chemically resistant glass or polyethylene and shall be prepared from salts sold specifically for use, either singly or in combination, as pH standards. The salts shall be dried for 1h at 110°C before use.
7.4 Hydrochloric Acid (0.100 N) - Prepare and standardize 0.100 N hydrochloric acid (HCl).
7.5 Phthalate Buffer Solution (0.05 M, pH = 4.01 at 25°C) - Dissolve 10.21 g of potassium hydrogen phthalate in distilled water and dilute to 1 L.
7.6 Phosphate Buffer Solution (0.025 M with respect to each phosphate salt, pH = 6.86 at 25°C) - Dissolve 3.40 g of potassium dihydrogen phosphate (KH2PO4) and 3.55 g of anhydrous disodium hydrogen phosphate (Na2HPO4) in distilled water and dilute to 1 L.
7.7 Potassium Chloride Electrolyte - Prepare a saturated solution of potassium chloride (KCl) in water.
8. Sampling
8.1 Sample the material in accordance with Standard Practice D1176.
