ASTM_D_1993_-_22.pdf

Designation:D199322Standard Test Method forPrecipitated Silica-Surface Area by Multipoint BET NitrogenAdsorption1This standard is issued under the fixed designation D1993;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 a procedure which is used tomeasure the surface area of precipitated hydrated silicas by theconventional Brunauer,Emmett,and Teller(BET)2theory ofmultilayergasadsorptionbehaviorusingmultipointdeterminations,similar to that used for carbon black in TestMethod D6556.This test method specifies the sample prepa-ration and treatment,instrument calibrations,required accuracyand precision of experimental data,and calculations of thesurface area results from the obtained data.1.2 This test method is used to determine the nitrogensurface area of precipitated silicas with specific surface areas inthe range of 10 to 500 m2/g.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.The minimum safety equipment should include protectivegloves,sturdy eye and face protection,and means to deal safelywith accidental mercury spills.1.5 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 Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:3D1799 Practice for Carbon BlackSampling PackagedShipmentsD1900 Practice for Carbon BlackSampling Bulk Ship-mentsD4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustriesD5604 Test Methods for Precipitated SilicaSurface Areaby Single Point B.E.T.Nitrogen AdsorptionD5900 Specification for Physical and Chemical Properties ofIndustry Reference Materials(IRM)D6556 Test Method for Carbon BlackTotal and ExternalSurface Area by Nitrogen Adsorption3.Significance and Use3.1 This test method is used to measure the surface area ofprecipitated,hydrated silicas that is available to the nitrogenmolecule using the multipoint(B.E.T.)method.Single pointnitrogen surface area is measured in accordance with the TestMethods D5604.3.2 Solids adsorb nitrogen,and under specific conditions,the adsorbed molecules approach a monomolecular layer.Thequantity in this hypothetical monomolecular layer is calculatedusing the BET equation.Combining this with the area occupiedby the nitrogen molecule yields the total surface area of thesolid.3.3 This test method measures the estimated quantity ofnitrogen in the monomolecular layer by adsorption at liquidnitrogen temperature and at several(at least five)partialpressures of nitrogen.3.4 Before a surface area determination can be made it isnecessary that the silica be stripped of any material which may1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand Rubber-like Materials and is the direct responsibility of Subcommittee D11.20on Compounding Materials and Procedures.Current edition approved Oct.1,2022.Published October 2022.Originallyapproved in 1991.Last previous edition approved in 2018 as D1993 18.DOI:10.1520/D1993-22.2Brunauer,Emmett,and Teller,Journal of the American Chemical Society,Vol60,1938,p.309.3For 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 StatesThis international standard was developed in accordance with internationally recognized principles on standardization 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.1already be adsorbed on the surface.The stripping of adsorbedforeign material eliminates two potential errors.The first erroris associated with the weight of the foreign material.Thesecond error is associated with the surface area that the foreignmaterial occupies.4.Apparatus4.1 Commercial instruments are available4for the measure-ment of nitrogen surface area by the multipoint BET method.These may be of the“flowing gas”or the“vacuum-volumetric”type.NOTE