ASTM D7638-10(R2021) pdf free download

ASTM D7638-10(R2021) pdf free download.Standard Test Method for Determination of Fatty Acids and Esters in Glycerin
1. Scope
1.1 This test method provides the quantitative determination of the fatty acid and ester content in purified glycerin by the titrimetric method. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This standard may involve hazardous materials, opera- tions and equipment. This standard does not purport to address all ofthe safety concerns, ifany, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific precautions are listed in Section 8. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
4. Significance and Use
4.1 Any residual fatty acid and esters (FA&E) should be present only at very low levels in purified glycerine. 4.2 This procedure requires the addition of a measured volume of sodium hydroxide, in excess of the amount actually needed to react with FA&E in the glycerine sample. After boiling, the excess sodium hydroxide is back titrated with standardized hydrochloric acid. The quantity of the substance being titrated is calculated as the difference between the volumes of the sodium hydroxide solution originally added, corrected by means ofa blank titration, and that was consumed by the titrant in the back titration. N OTE 1—The standardized solutions for sodium hydroxide and hydro- chloric acid are commercially available.
5. Apparatus
5.1 Standard Type A Glassware. 5.2 Erlenmeyer flask, 200 mL to 250 mL, alkali-resistant with a standard tapered 24/40 ground glass neck joint, or equivalent. 5.3 Microburette having a capacity of 5 mL, graduated to 0.02 mL and calibrated to meet the National Institute of Standards and Technology (NIST) specification. An automatic titrator with a minimum capacity of 5 mL can also be used. 5.4 Pipette, standard or automatic that can accurately de- liver 5 mL 6 0.01 mL. 5.5 Air reflux condenser with standard taper ground glass joint which fits the Erlenmeyer flask in 5.1. Minimum length, 550 mm.
6. Purity of Reagents and Water
6.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents 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 ofWater—Unless indicated otherwise, references to water shall be understood to mean Type II reagent water as defined in Specification D1193. N OTE 2—The presence ofcarbon dioxide can introduce errors; therefore it is advisable to prepare 500 mL of water by boiling for 5 min. Cool to room temperature. Check the pH of the distilled water before use. The pH should be 7.0 6 0.1. If not, adjust the pH with 0.1 N sodium hydroxide (NaOH) or 0.1 N hydrogen chloride (HCl), whichever is appropriate. Store the freshly boiled and neutralized water in a tightly closedcontainer.
7. Reagents
7.1 Phenolphthalein Solution—(See Note 2.) Dissolve 1 g of phenolphthalein in 100 mL of ethanol (95 %), methanol or isopropanol. This solution can be purchased. 7.2 Hydrochloric Acid, 0.5 N, aqueous solution—(See Note 1 and Note 2.) To a 1000 mL volumetric flask containing 40 mL of water, slowly add 43 mL of concentrated hydrochlo- ric acid. Cool, and add water to volume. Standardize the solution to an accuracy of 60.001 N. 7.3 Sodium Hydroxide, 0.5 N, aqueous solution—(See Note 1 and Note 2.) Dissolve 22.0 g of NaOH in water and dilute to 1 L. Allow to stand overnight. Siphon the liquid into a clean bottle. Standardize accurately to 60.001 N with potassium acid phthalate. The standardized sodium hydroxide solution should be protected against evaporation and absorption of carbon dioxide (CO 2 ) from the air. N OTE 3—The normality of the hydrochloric acid and sodium hydroxide solutions may be in the range of 0.5 N 6 0.05 N. 7.4 Freshly boiled water, or equivalent. (See 6.2.)