ASTM_D_6423_-_14.pdf

Designation:D642314Standard Test Method forDetermination of pHe of Denatured Fuel Ethanol andEthanol Fuel Blends1This standard is issued under the fixed designation D6423;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.Scope*1.1 This test method covers a procedure to determine ameasure of the acid strength of high ethanol content fuels.These include denatured fuel ethanol and ethanol fuel blends.The test method is applicable to denatured fuel ethanol andethanol fuel blends containing ethanol at 51%by volume,ormore.1.2 Acid strength as measured in this test method is definedas pHe.A pHe value for alcohol solutions is not comparable topH values of water solutions.1.2.1 The value of pHe measured will depend somewhat onthe fuel blend,the stirring rate,and the time the electrode is inthe fuel.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3.1 Hydrogen ion activity in water is expressed as pH andhydrogen ion activity in ethanol is expressed as pHe.1.4 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.Referenced Documents2.1 ASTM Standards:2D1193 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 FuelD5798 Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines3.Terminology3.1 For general terminology,refer to Terminology D4175.3.2 Definitions:3.2.1 denaturants,nmaterials added to ethanol to make itunsuitable for beverage use under a formula approved by aregulatory agency to prevent the imposition of beveragealcohol tax.D48063.2.1.1 DiscussionDenaturants are only those materialsadded by the denaturer to comply with the approved formula;any materials absorbed later are not denaturants.3.2.2 denatured fuel ethanol,nfuel ethanol made unfit forbeverage use by the addition of denaturants under formula(s)approved by the applicable regulatory agency to prevent theimposition of beverage alcohol tax.D48063.2.3 ethanol,nethyl alcohol,the chemical compound,C2H5OH.3.2.4 ethanol fuel blend,na blend of ethanol and hydro-carbons for use in flexible-fuel automotive spark-ignitionengines of which the ethanol portion is 51%to 83%byvolume.D57983.2.5 flexible-fuel vehicle,na vehicle designed to operateon either unleaded gasoline or ethanol fuel blends or mixturesof both.D57983.2.6 fuel ethanol,na grade of undenatured ethanol withother components common to its production(including water)that do not affect the use of the product as a component forautomotive spark-ignition engine fuels.D48063.2.7 hydrocarbon,na compound composed solely ofhydrogen and carbon.D57983.3 Definitions of Terms Specific to This Standard:3.3.1 pHe,na measure of the acid strength of ethanol-hydrocarbon blends defined by this apparatus and procedure.4.Summary of Test Method4.1 The sample is analyzed at room temperature using aspecified electrode system and a pH meter with an input1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.A0.02 on Oxygenated Fuels and Components.Current edition approved Dec.15,2014.Published February 2015.Originallyapproved in 1999.Last previous edition approved in 2008 as D6423 08.DOI:10.1520/D6423-14.2For 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 at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 impedance 1012(ohms).Meters designed for use withion-specific electrodes normally meet this criteria.4.2 Readings are taken at exactly 30 s because the meterreading will change throughout the analysis due to glass-electrode voltage drift caused by dehydration of the glass-electrode membrane.Because alcohol dehydrates the glass-electrode membrane,time spent soaking in alcohol solutionshould be minimized.4.3 The electrode is soaked in water-based pH 7 bufferbetween readings to prepare it for the next sample.Thisrehydrates the glass electrode,a necessary step to preserve theelectrodes response characteristics.4.4 The electrodes are cleaned/rehydrated at least every tensamples by altern