1、Designation: D5555 95 (Reapproved 2011)Standard Test Method forDetermination of Free Fatty Acids Contained in Animal,Marine, and Vegetable Fats and Oils Used in Fat Liquorsand Stuffing Compounds1This standard is issued under the fixed designation D5555; the number immediately following the designati
2、on 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 determi
3、nation of the freefatty acid content of fats and oils.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespon
4、sibility 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 the determination of thefree fatty acids contained in animal, marine, and ve
5、getable fatsand oils for the purpose of quality assurance.3. Apparatus and Reagents3.1 Oil Sample Bottles, 115 or 230 mL (4 or 8 oz) or 250 mLErlenmeyer flasks.3.2 Ethyl Alcohol, 95 %. The alcohol shall give a definite,distinct, and sharp end-point with phenolphthalein and shall beneutralized with a
6、lkali to a faint but permanent pink color justbefore using. (Isopropanol, 99 %, may be used as an alternatesolvent with crude and refined vegetable oils.)3.3 Phenolphthalein Indicator Solution, 1 % in 95 % alco-hol.3.4 Sodium Hydroxide Solution, accurately standardized.4. Procedure4.1 Use Table 1 to
7、 determine the quantities to be used withvarious ranges of fatty acids.4.2 The sample shall be entirely liquid and well mixedbefore weighing. Then weigh the designated sample size intoan oil-sample bottle or Erlenmeyer flask; add to that thespecified amount of hot, neutralized alcohol and 2 mL ofind
8、icator.4.3 Shaking vigorously, make the titration with alkali to theappearance of the first permanent pink color of the sameintensity as that of the neutralized alcohol before adding thesample. The color shall persist for 30 s.5. Calculation and Report5.1 Report the free fatty acids in percent, by w
9、eight:% free fatty acids 5mL of alkali 3 N 3 28.2weight of sample(1)5.2 Reference this test method in the test report.5.3 The free fatty acids are frequently expressed in terms ofacid value instead of percent free fatty acids. The acid value isdefined as the number of milligrams of KOH necessary ton
10、eutralize1gofsample. To convert percent free fatty acids (asoleic) to acid value, multiply the former by 1.99.6. Precision 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 i
11、nclusion 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 us
12、e.7. Keywords7.1 fats and oils; free fatty acids; leather1This 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
13、H 30-1957).Current edition approved Jan. 1, 2011. Published March 2011. Originallyapproved in 1994. Last previous edition approved in 2006 as D5555 95(2006).DOI: 10.1520/D5555-95R11.TABLE 1 Suggested Quantity of Material to TestSample, g Alcohol, mL Normality of AlkaliFree Fatty AcidRange (%)56.4 6
14、0.2 50 0.1 0.0 to 0.228.2 6 0.2 50 0.1 0.2 to 1.07.05 6 0.05 75 0.25 1.0 to 30.07.05 6 0.05 100 0.25 or 1.0 30.0 to 50.03.525 6 0.001 100 1.0 50.0 to 100.01Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.ASTM International takes no po
15、sition 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 rights, are entirely their own responsibi
16、lity.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 additional standardsand should be addressed to A
17、STM 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 ASTM Committee on Standards, at the addres
18、s 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D5555 95 (2011)2
