1、Designation:D779515Standard 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 numbe
2、r in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This test method covers the determination of acidity asacetic acid(see Specification D4806)in commonly availablegrades of denatured ethanol,and
3、 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 Procedure ADeveloped specifically for measure-ment of acidity by potentiometric titration.This is the refereemethod.1
4、.1.2 Procedure 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 informat
5、ion 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 conce
6、rns,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 Documen
7、ts2.1 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 FuelD6708
8、Practice for Statistical Assessment and Improvementof Expected Agreement Between Two Test Methods thatPurport to Measure the Same Property of a MaterialE200 Practice for Preparation,Standardization,and Storageof Standard and Reagent Solutions for Chemical Analysis3.Terminology3.1 Definitions:3.1.1 a
9、cidity,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
10、 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 Procedure A,or by col
11、or endpoint titration,as specified in Procedure 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 containadditive
12、s 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 v
13、ery low level.5.2 Acceptable levels of acidity in ethanol or ethanol blendscan vary with different specifications but in general it is below200 mg/kg(ppm).Knowledge of the acidity can be required toestablish whether the product quality meets specification.1This test method is under the jurisdiction
14、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.15,2015.Published February 2016.Originallyapproved in 2012.Last previous edition approved in 2012 as D
15、7795 12.DOI:10.1520/D7795-15.2For 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.*A Summary of Changes section appears
16、 at the end of this standardCopyright 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-quentlyenoughtodetectconcentrationchangesof0.00