ASTM D664 for acid number of petroleum products
ASTM D664 for acid number of petroleum products by potentiometric titration
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.
7.1.1 Commercially available solutions may be used in place of laboratory preparations provided the solutions have been certified as being equivalent.
7.1.2 Alternate volumes of the solutions may be prepared, provided the final solution concentration is equivalent.
7.2 Purity of Water - Unless otherwise indicated, reference to water shall be understood to mean reagent water that meets the requirements of either Type I, II, or III of Specification D1193.
7.3 Ethanol, (Warning - Flammable and toxic, especially when denatured.)
7.4 Hydrochloric Acid (HCl) - Relative density 1.19. (Warning - Corrosive, causes burns.)
7.5 Lithium Chloride, LiCl.
7.6 Lithium Chloride Electrolyte, Prepare a 1M–3M solution of lithium chloride (LiCl) in ethanol.
7.7 Methanol, (Warning - Flammable. Toxic if swallowed.)
7.8 Potassium Hydroxide, (Warning - Causes severe burns.)
7.9 Propan-2-ol, Anhydrous, (less than 0.1 % H2O). (Warning - Flammable.) If adequately dry reagent cannot be procured, it can be dried by distillation through a multiple plate column, discarding the first 5 % of material distilling overhead and using the 95 % remaining. Drying can also be accomplished using molecular sieves such as Linde Type 4A, by passing the solvent upward through a molecular sieve column using one part of molecular sieve per ten parts of solvent.
NOTE 7 - It has been reported that, if not originally inhibited against it, propan-2-ol can contain peroxides. When this occurs, an explosion is possible when the storage of the vessel or other equipment such as a dispensing bottle, is near empty and approaching dryness.
7.10 Toluene, (Warning - Flammable.)
7.11 Hydrochloric Acid Solution, Standard Alcoholic, (0.1 mol/L). (Warning - See 7.4 and 7.9.) Mix 9 mL of hydrochloric (HCl, relative density 1.19) acid with 1 L of anhydrous propan-2-ol. Standardize frequently enough to detect concentration changes of 0.0005 by potentiometric titration of approximately 8 mL (accurately measured) of the 0.1-mol/L alcoholic KOH solution diluted with 125 mL of CO2-free water.
7.12 Commercial Aqueous pH 4, pH 7 and pH 11 Buffer Solutions - These solutions shall be replaced at regular intervals consistent with their stability or when contamination is suspected. Information relating to their stability should be obtained from the manufacturer.
7.13 Potassium Hydroxide Solution, Standard Alcoholic, (0.1 mol//L). (Warning - See 7.8 and 7.9.) Add 6 g of potassium hydroxide (KOH) to approximately 1 L of propan-2-ol. Boil gently for 10 min to effect solution. Allow the solution to stand for two days and then filter the supernatant liquid through a fine sintered-glass funnel. Store the solution in a chemically resistant bottle. Dispense in a manner such that the solution is protected from atmospheric carbon dioxide (CO2) by means of a guard tube containing soda lime or soda non-fibrous silicate absorbents and such that it does not come into contact with cork, rubber, or saponifiable stopcock grease. Standardize frequently enough to detect concentration changes of 0.0005 by potentiometric titration of weighed quantities of potassium acid phthalate dissolved in CO2-free water.
7.14 Titration Solvent - Add 5 more or less 0.2 mL of water to 495 more or less 5 mL of anhydrous propan-2-ol and mix well. Add 500 more or less 5 mL of toluene. (Warning - Flammable.) The titration solvent should be made up in large quantities, and its blank value determined daily by titration prior to use.
7.15 Chloroform, (Warning - Flammable. Hazardous material.)
