ASTM_D_1980_-_87_1998.pdf

Designation:D 1980 87(Reapproved 1998)Standard Test Method forAcid Value of Fatty Acids and Polymerized Fatty Acids1This standard is issued under the fixed designation D 1980;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of acid value(a measure of the acidity or amount of free fatty acids)and isapplicable to all fatty acids and polymerized fatty acids.1.2 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:D 1193 Specification for Reagent Water23.Terminology3.1 Definitions:3.1.1 acid valuethe number of milligrams of potassiumhydroxide required to neutralize the fatty acids in 1 g ofsample.4.Significance and Use4.1 Drying oils are composed primarily of triglycerides offatty acids,and normally contain low amounts of free fattyacids.However they can be saponified to produce essentiallyonly fatty acids.This test method is used to determine theacidity(acid value)of the fatty acids and is therefore indicativeof the amount of free fatty acids in a sample.4.2 This test method is not to be used as a quality require-ment since it measures all acidic components and does notdistinguish between fatty acids of different composition.5.Reagents5.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended thatall reagents shall conform to the Specifications of the Com-mittee on Analytical Reagents of the American ChemicalSociety,where such specifications are available.3Other gradesmay be used,provided it is first ascertained that the reagent isof sufficiently high purity to permit its use without lesseningthe accuracy of the determination.5.2 Purity of WaterUnless otherwise indicated,referencesto water shall be understood to mean water conforming to TypeII of Specification D 1193.5.3 Ethyl Alcohol,Neutral(95%)Use 95%ethyl alcoholor neutral denatured alcohol conforming to Formula No.30 orNo.3A of the U.S.Bureau of Alcohol,Tobacco,and Firearms.Boil and neutralize to the phenolphthalein end point with alkalijust before using.5.4 Phenolphthalein Indicator Solution(10 g/L)(Note 1)Dissolve 1 g of phenolphthalein in 100 mL of ethanol(95%),methanol,or isopropanol.NOTE1A“masked phenolphthalein indicator”may be used withoff-color materials.Prepare by dissolving 1.6 g of phenolphthalein and 2.7g of methylene blue in 500 mL of alcohol conforming to 5.3.Adjust thepH with sodium hydroxide(NaOH)or potassium hydroxide(KOH)solution so that the greenish-blue color is faintly tinted with purple.Thecolor change is from green to purple when going from acid to alkaline.5.5 Potassium Hydroxide or Sodium Hydroxide,StandardSolution(0.5 N):Prepare a stock concentrated solution bydissolving 560 g of potassium hydroxide(KOH)or 425 g ofsodium hydroxide(NaOH)in 1 L of water.5.5.1 Allow this solution to cool and settle in a stopperedbottle for several days.Decant the clear liquid from thecarbonate precipitate into another clean bottle.Add clearbarium hydroxide(Ba(OH)2)solution until no further precipi-tate forms.Again allow to settle until clear.Draw off about 875mL and dilute to 10 L with freshly boiled reagent water.Preserve in a stock bottle provided with a large drying tubefilled with soda-lime.5.5.2 Standardize by titrating against potassium acid phtha-late(National Bureau of Standards Acid Potassium PhthalateNo.84),using phenolphthalein as indicator.This solution isapproximately 0.5 N but instead of adjusting it to a specificvalue,determine the exact normality and use in the calcula-tions.1This test method is under the jurisdiction of ASTM Committee D-1 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.32 on Drying Oils.Current edition approved June 26,1987.Published August 1987.Originallypublished as D 1980 61.Last previous edition D 1980 85.2Annual Book of ASTM Standards,Vol 11.01.3Reagent Chemicals,American Chemical Society Specifications,AmericanChemical Society,Washington,DC.For suggestions on the testing of reagents notlisted by the American Chemical Society,see Analar Standards for LaboratoryChemicals,BDH Ltd.,Poole,Dorset,U.K.,and the United States Pharmacopeiaand National Formulary,U.S.Pharmacopeial Convention,Inc.(USPC),Rockville,MD.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTM6.Procedure6.1 Transfer about 5 g of the sample,weighed to 1 mg to a500-mL Erlenmeyer flask a