ASTM_D_5554_-_15.pdf

Designation:D555415Standard Test Method forDetermination of the Iodine Value of Fats and Oils1This standard is issued under the fixed designation D5554;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 iodinevalue 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 the determination of theiodine value of fats and oils that do not contain conjugateddouble bonds.The iodine value is a measure of the unsaturationof fats and oils and is expressed in terms of the number ofcentigrams of iodine absorbed per gram of sample.3.Apparatus and Reagents3.1 Glass-Stoppered Bottles or Wide Mouth ErlenmeyerFlasks,500 mL.Wide mouth bottles or flasks are essential ifstirring is done by mechanical means.3.2 Glass-Stoppered Volumetric Flasks,conforming toNIST tolerances2and accurately calibrated to contain 1000mL.3.3 Pipette,20 mL.3.4 Two Pipettes,25 mL.One pipette is reserved for usewith the standard potassium dichromate solution and shallconform to NIST tolerances2and be calibrated to deliver 25mL.3.5 Glacial Acetic Acid,A.C.S.grade.The permanganatetest shall be applied to be sure that this specification is met.3.5.1 Two millilitres of the glacial acetic acid shall bediluted with 10 mL of distilled water and 0.1 mL of 0.1 NKMnO4shall be added.The pink color shall not be entirelydischarged within 2 h.3.6 Potassium Iodide,A.C.S.grade.3.7 Chlorine,99.8%.Satisfactory commercial grades areavailable in cylinders,but this gas must be dried by passingthrough sulfuric acid(sp.gr.1.84)before introducing into theiodine solution.3.7.1 Chlorine may be prepared by allowing hydrochloricacid(sp.gr.1.19)to drop onto potassium permanganate or ona mixture of potassium permanganate and manganese dioxide.The gas thus generated shall be led through a glass tube intosulfuric acid(sp.gr.1.84)and then into the iodine solution.3.8 Carbon Tetrachloride,A.C.S.grade.(WarningCarbon Tetrachloride is a known carcinogen.It is toxic byinhalation,ingestion and skin absorption.Always handle Car-bon Tetrachloride inside a fume hood.Use only with adequateventilation.3.9 Cyclohexane3,A.C.S.grade.3.10 Reagent for Diluting SamplePrepare by mixing freshcyclohexane and glacial acetic acid,1:1,v/v.(After mixing,verify the absence of oxidizable matter in the reagent byshaking 10 mL of the reagent with 1 mL of saturated aqueouspotassium dichromate solution and 2 mL of concentratedsulfuric acid:no green coloration should appear.A greencoloration indicates presence of oxidizable matter,so discardand remix using fresh cyclohexane.)3.11 Hydrochloric Acid,A.C.S.grade,sp.gr.1.19.3.12 Soluble Starch,of suitable sensitivity.3.12.1 The test for starch sensitivity shall be made byadding,while stirring,200 mL of boiling water to a paste madewith 1 g of starch in a small amount of water.After placing 5mL of this solution in 100 mL of water,add 0.05 mL of 0.1 Niodine solution.The deep blue color produced must be dis-charged by 0.05 mL of 0.1 N sodium thiosulfate.3.13 Potassium Dichromate,A.C.S.grade,shall be finelyground and dried to constant weight at about 110C before1This 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 32-1957).Current edition approved Sept.1,2015.Published October 2015.Originallyapproved in 1994.Last previous edition approved in 2011 as D5554 95(2011).DOI:10.1520/D5554-15.2Available from National Institute of Standards and Technology,(NIST),Gaithersburg,MD 20899.3Comparison study showed excellent agreement between Carbon Tetrachlorideand Cyclohexane(ISO/IUPAP Smalley program).Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 using.(A standard sample of potassium dichromate with acertificate of analysis may be obtained from NIST.2Thissample is strongly recommended as the primary standard forthis test method.The dichromate should be treated as directedin the certificate of analysis accompanying the sample.)3.14 Sodium Thiosulfate(Na2S2O35H2O),A.C.S.grade.3.15 Iodine,A.C.S.grade.3.16 Potassium Iodide Solution,prepared by dissolving 150g in distilled water and making up to 1 L.3.17 Starch Indicator Soluti