ASTM_D_7795_-_12.pdf

Designation:D779512Standard Test Method forAcidity in Ethanol and Ethanol Blends by Titration1This standard is issued under the fixed designation D7795;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 acidity asacetic acid(see Specification D4806)in commonly availablegrades of denatured ethanol,and ethanol blends with gasolineranging from E95 to E30.This test method is used fordetermining low levels of acidity,below 200 mg/kg(ppmmass),with the exclusion of carbon dioxide.1.1.1 Test Method ADeveloped specifically for measure-ment of acidity by potentiometric titration.This is the refereemethod.1.1.2 Test Method BDeveloped specifically for measure-ment of acidity by color end point titration.1.2 The ethanol and ethanol blends may be analyzed di-rectly by this test method without any sample preparation.1.3 Review the current and appropriate Material Safety DataSheets(MSDS)for detailed information concerning toxicity,first aid procedures,and safety precautions and proper personalprotective equipments.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 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.Some specifichazards statements are given in Section 7 on Hazards.2.Referenced Documents2.1 ASTM Standards:2D770 Specification for Isopropyl AlcoholD1193 Specification for Reagent WaterD4175 Terminology Relating to Petroleum,PetroleumProducts,and LubricantsD4806 Specification for Denatured Fuel Ethanol for Blend-ing with Gasolines for Use as Automotive Spark-IgnitionEngine FuelD6300 Practice for Determination of Precision and BiasData for Use in Test Methods for Petroleum Products andLubricantsE200 Practice for Preparation,Standardization,and Storageof Standard and Reagent Solutions for Chemical Analysis3.Terminology3.1 Definitions:3.1.1 acidity,nthe quality,state,or degree of being acid.D41753.1.1.1 DiscussionThe amount of acid titrated with a base(NaOH or KOH)in a sample of ethanol or ethanol blend withgasoline,calculated as acetic acid in mg/kg(ppm mass).3.2 Abbreviations:3.2.1 KHC8H4O4KHP-Potassium Acid Phthalate4.Summary of Test Method4.1 Samples are purged with nitrogen prior to and duringtitration for the elimination of carbon dioxide and then a knownamount of ethanol or ethanol blend sample is analyzed poten-tiometrically either using a monotonic or dynamic end pointtitrant addition,as specified in Test Method A,or by color endpoint titration,as specified in Test Method B,using a base(NaOH)solution.Acid content is calculated as milligrams ofacetic acid per kilogram of sample.5.Significance and Use5.1 This test method measures acidity in ethanol or ethanolblends quantitatively.Denatured fuel ethanol may containadditives such as corrosion inhibitors and detergents as well ascontaminants from manufacturing that can affect the acidity offinished ethanol fuel.Very dilute aqueous solutions of lowmolecular mass organic acids,such as acetic acid,are highlycorrosive to many metals.It is important to keep such acids ata very low level.5.2 Acceptable levels of acidity in Ethanol or Ethanolblends can vary with different specifications but in general it isbelow 200 mg/kg(ppm).Knowledge of the acidity can berequired to establish whether the product quality meets speci-fication.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.06 on Analysis of Liquid Fuels and Lubricants.Current edition approved Dec.1,2012.Published February 2013.DOI:10.1520/D7795-12.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.Interferences6.1 Basic solutions will absorb carbon dioxide from the airto produce carbonate ions in the titrant and change theconcentration of the titrant.Care should be taken to minimizeexposure of basic titrants to the air as much as possible.Verifythe concentration of the titrant(standardize the titrant)fre-quently enough to detect concentration changes of 0.0005 Mand especially if prolonged exposure to the air occurs.6.2 Minimize exposure of the ethanol or ethanol blendsamples to the air to avoid contamination by carbon diox