1、Designation:D7318191Standard Test Method forExistent Inorganic Sulfate in Ethanol by PotentiometricTitration1This standard is issued under the fixed designation D7318;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last r
2、evision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.NOTESubsection 11.2.1 was corrected and the yeardate changed on February 14,2019.Footnote 1 was corrected editorially in December 2019.1.Sco
3、pe*1.1 This test method covers a potentiometric titration pro-cedure for determining the existent inorganic sulfate content ofhydrous,anhydrous ethanol,and anhydrous denatured ethanol,which is added as a blending agent with spark ignition fuels.Itis intended for the analysis of denatured ethanol sam
4、plescontaining between 1.0 mg kg to 20 mg kg existent inorganicsulfate.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
5、is theresponsibility of the user of this standard to establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.Material Safety Data Sheets are available for reagents andmaterials.Review them for hazards prior to usage.1.4
6、 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Tra
7、de(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD4052 Test Method for Density,Relative Density,and APIGravity of Liquids by Digital Density MeterD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling
8、of Petroleum andPetroleum ProductsD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System Performance3.Terminology3.1 Definitions:3.1.1 existent inorganic sulfate,ninorganic sulfate speciesactually present in the sample at the
9、 time of analysis with nooxidation treatment.3.1.1.1 DiscussionSpecifically in this test method,inor-ganic sulfate is present as sulfate in ethanol.3.1.2 inorganic sulfate,nsulfate(SO42)species presentas sulfuric acid,ionic salts of this acid,or mixtures of these.4.Summary of Test Method4.1 An ethan
10、ol sample containing inorganic sulfate istitrated in ethanolic medium with a standard lead nitratesolution.Lead sulfate precipitate is formed during the titration.Perchloric acid is added to remove possible interference fromcarbonate.The endpoint is signaled by an increase in lead ionactivity,as mea
11、sured by a lead-selective electrode.5.Significance and Use5.1Ethanol is used as a blending agent added to gasoline.Sulfates are indicated in filter plugging deposits and fuelinjector deposits.When fuel ethanol is burned,sulfates maycontribute to sulfuric acid emissions.Ethanol acceptability foruse d
12、epends on the sulfate content.Sulfate content,as mea-sured by this test method,can be used as one measure ofdetermination of the acceptability of ethanol for automotivespark-ignition engine fuel use.6.Apparatus6.1 Potentiometric Titration AssemblyA titration assem-bly consisting of an automatic titr
13、ator fitted with a lead1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.03 on Elemental Analysis.Current edition approved Feb.14,2019.Published February 2019.Originallyapproved in 20
14、07.Last previous edition approved in 2013 as D7318 13.DOI:10.1520/D7318-19E01.2For 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 A
15、STM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardizati
16、on established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.ion-selective electrode,a double-junction reference electrode,buret,and stirring is used.Stirring may be accomplished bymeans of magnetic or propeller type stirrer mechanisms.Theburet size should ideally be 10 mL or 20 mL.6.2 Reference ElectrodeA double junction reference elec-trode with the inner el
