1、Designation: D 5558 95 (Reapproved 2006)Standard Test Method forDetermination of the Saponification Value of Fats and Oils1This standard is issued under the fixed designation D 5558; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、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 the saponi-fication value of fats and oils.1.2 The values st
3、ated in SI units are to be regarded as thestandard.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
4、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, Corning2alka
5、li 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 a
6、lcohol (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 potassium hydrox-ide, 40 g of potassium hydroxide, low in
7、 carbonate, shall bedissolved in 1 L of the distilled alcohol, keeping the tempera-ture below 15.5C (60F) while the alkali is being dissolved.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
8、 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 bl
9、ank determination and conduct simulta-neously 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
10、rise tothe top of the condenser or there may be some loss.NOTE 1Some 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 necessari
11、ly 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 p
12、ink color has just disap-peared.5. Calculation and Report5.1 Calculate the saponification number as follows:saponification value 528.05A 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
13、 and Bias6.1 This test method is adopted from the procedures of theAmerican Leather ChemistsAssociation where it has long beenin use and was approved for publication before the inclusion of1This test method is under the jurisdiction of ASTM Committee D31 on Leatherand is the direct responsibility of
14、 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 April 1, 2006. Published April 2006. Originallyapproved in 1994. Last previous edition approved in 2001 as D 5558 95(2001).2Product
15、is widely available commercially.3Alternately, commercially available potassium hydroxide solution 0.5 Nmmethanol is said to work satisfactorily.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.precision and bias statements was mandat
16、ed. 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; saponifica
17、tion 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 of the validity of any such patent rights, and the riskof infringement of such r
18、ights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for addition
19、al standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the AS
20、TM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 5558 95 (2006)2
