ASTM_D_5558_-_95_2011.pdf

Designation:D555895(Reapproved 2011)Standard Test Method forDetermination of the Saponification Value of Fats and Oils1This standard is issued under the fixed designation D5558;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of the saponi-fication value of fats and oils.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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.Significance and Use2.1 This test method is intended for use in the determinationof the saponification value of fats and oils used in themanufacture of fat liquors for the purpose of quality assurance.3.Apparatus and Reagents3.1 Erlenmeyer Flasks,Corning2alkali resistant,Kimbleresistant,or equivalent,250 or 300 mL.3.2 Air Condensers,minimum length 650 mm.3.3 Water Bath or a Hot Plate,with variable heat control.3.4 Hydrochloric Acid,0.5 N,accurately standardized.3.5 Alcoholic Potassium Hydroxide,3added to a 2-L flaskfrom 1 to 1.5 L of 95%ethyl alcohol(U.S.S.D.Formula 3A2is permitted)and a few grams(5 to 10 g)of potassiumhydroxide.After boiling under a reflux condenser on a waterbath for 30 to 60 min,the alcohol shall be distilled andcollected.For the preparation of alcoholic potassiumhydroxide,40 g of potassium hydroxide,low in carbonate,shall be dissolved in 1 L of the distilled alcohol,keeping thetemperature below 15.5C(60F)while the alkali is beingdissolved.This solution should remain clear.4.Procedure4.1 Melt the sample,if not already liquid,and filter throughfilter paper to remove any impurities and the last traces ofmoisture.The sample must be completely dry.4.2 Accurately weigh a sample,of such size(usually 4 to 5g)that the back titration is 45 to 55%of the blank,and 50 mLof the alcoholic KOH is added with a pipette,allowing thepipette to drain for a definite period of time.4.2.1 Prepare a blank determination and conduct simultane-ously with the sample.4.3 Connect air condensers to the flask and boil the solutiongently but steadily until the sample is completely saponified.This usually requires approximately 1 h for normal samples.Take care that the vapor ring in the condenser does not rise tothe top of the condenser or there may be some loss.NOTE1Some samples particularly difficult to saponify may requiremore than 1 h.This can only be determined by trial.Clarity andhomogeneity of the test solution are partial indicators of the completesaponification,but they are not necessarily absolute criteria.4.4 After the flask and condenser have cooled somewhat,but not sufficiently to jell the contents,wash down the inside ofthe condenser with a little distilled water.Then disconnect theflask,add approximately 1 mL of indicator,and titrate thesolution with 0.5 N HCl until the pink color has just disap-peared.5.Calculation and Report5.1 Calculate the saponification number as follows:saponification value528.05A 2 B!weight of sample(1)where:A=titration of blank,andB=titration of sample.5.2 Reference this test method as the procedure used in thetest report.6.Precision and Bias6.1 This test method is adopted from the procedures of theAmerican Leather ChemistsAssociation where it has long been1This test method is under the jurisdiction of ASTM Committee D31 on Leatherand is the direct responsibility of Subcommittee D31.08 on Fats and Oils.This testmethod was developed in cooperation with the American Leather Chemists Assn.(Method H 31-1957).Current edition approved Jan.1,2011.Published March 2011.Originallyapproved in 1994.Last previous edition approved in 2006 as D5558 95(2006).DOI:10.1520/D5558-95R11.2Product is widely available commercially.3Alternately,commercially available potassium hydroxide solution 0.5 Nmmethanol is said to work satisfactorily.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 in use and was approved for publication before the inclusion ofprecision and bias statements was mandated.The originalinterlaboratory test data are no longer available.The user iscautioned to verify by the use of reference materials,ifavailable,that the precision and bias(or reproducibility)of thistest method is adequate for the contemplated use.7.Keywords7.1 fats and oils;leather;saponification valueASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard.Users of this standard are expressly advised that determination