ASTM D1287 Standard Test Method for pH of Engine Coolants and Antirusts
5. Apparatus
5.1 The pH meter, glass electrode, and calomel electrode, shall be as specified in the Annex.
NOTE 4 - In pH operation, the meter may be set up to perform one-, two- or up to five-point standardizations or may he set up to automatically recognize U.S. standard (pH 4, 7 and 10) buffers, NIST/International (pH 1.68, 4.01, 6.86, 9.18 and 12.46) buffers, or a custom user-centered set of buffers, or both.
6. Reagents
6.1 Parity 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 arc 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 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 its equivalent while cooling and in storage. The pH of the water shall be between 6.2 and 7.2 at 25°C.
6.3 Standard Buffer Solutions - The buffer solutions for calibrating the pi I meter and electrode pair shall be prepared from salts sold specifically for use. either singly or in combination. as pH standards. The salts shall be dried for 1 h at 110°C before use. except in the ease of borax which shall be used as the decahydrate. The solutions with pH less than 9.5 shall be stored in chemically resistant bottles. The alkaline phosphate solution shall be stored in glass bottles coaled on the side with paraffin.
NOTE 5 - Commercially available buffer tablets or prepared buffer solutions may he used.
6.4 Standard Buffer Solution pH = 1.68, (Buffer pH 1.68 from Fisher Scientific FC Part Number 13-620-836) or equivalent could be used.
6.5 Potassium Hydrogen Phthalate Buffer Solution (0.05 M, pH = 4.01 at 25°C) - Dissolve 10.21 g of potassium hydrogen phthalate (KHC8H4O4,) in water, and dilute to 1 L. Standard Buffer Solution pH = 4.0, Potassium Hydrogen Phthalate (Red, pH 4.01) from Fisher Scientific (FC Part Number: SB 101-500; NIST-SRM 185 g) or equivalent could be used.
6.6 Neutral 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 water and dilute to 1 L. Standard Buffer Solution pH = 6.86, Potassium Phosphate (pH 6.86 from Fisher Scientific, or NIST-SRM 186 le/lle) or equivalent could be used.
6.7 Standard Buffer Solution pH = 7.0, Potassium Phosphate Monobasic (Yello, pH 7.00) from Fisher Scientific (FC Part Number: SB 107-500) or equivalent could be used.
6.8 Borax Buffer Solution (0.01 M, pH = 9.18 at 25°C) - Dissolve 3.81 g of disodium tetraborate decahydrate (Na2B4O7·10H2O) in water, and dilute to 1 L. Protect this solution from atmospheric carbon dioxide; stopper the bottle at all limes except when actually in use. Standard Buffer Solution pH = 9.18. Sodium Tetraborate x 10 H2O (borax) (pH 9.18) from Fisher Scientific or XIST-SRM 187c) or equivalent could be used.
6.9 Standard Buffer Solution pH = 10.00, Potassium Carbonate. Potassium (Blue. Buffer pH 10.00 from Fisher Scientific FC Part Number SB 115-500) or equivalent could be used.
6.10 Alkaline Phosphate Buffer Solution (0.01 M trisodium phosphate, pH = 11.72 at 25°C) - Dissolve 1.42 g of anhydrous disodium hydrogen phosphate (Na2HPO4) in 100 mL of a 0.1 M carbonate-free solution of sodium hydroxide and dilute to I L with water.
6.11 Standard Buffer Solution pH = 12.46, (Buffer pH 12.46 from Fisher Scientific FC Part Number 13-620-837) or equivalent could be used.
6.12 Potassium Chloride Electrolyte - Prepare a saturated solution of potassium chloride (KCI) in water.
7. Sampling
Sample material in accordance with Practice D1176.
