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Designation: D6556 − 14Standard Test Method forCarbon Black—Total and External Surface Area by NitrogenAdsorption 1This standard is issued under the f i xed designation D6556; 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 the totalsurface area by the Brunauer, Emmett, and Teller (B.E.T. NSA)theory of multilayer gas adsorption behavior using multipointdeterminations and the external surface area based on thestatistical thickness surface area method.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 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. (The minimumsafety equipment should include protective gloves, sturdy eyeand face protection).2. Referenced Documents2.1 ASTM Standards: 2D1799 Practice for Carbon Black—Sampling PackagedShipmentsD1900 Practice for Carbon Black—Sampling Bulk Ship-mentsD3765 Test Method for Carbon Black—CTAB (Cetyltrim-ethylammonium Bromide) Surface Area (Withdrawn2007) 3D4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustries3. Summary of Test Method3.1 The total and external surface areas are measured byevaluating the amount of nitrogen adsorbed, at liquid nitrogentemperature, by a carbon black at several partial pressures ofnitrogen. The adsorption data is used to calculate the NSA andSTSA values.4. Signif i cance and Use4.1 This test method is used to measure the total andexternal surface area of carbon blacks based on multipointnitrogen adsorption. The NSA measurement is based on theB.E.T. theory and it includes the total surface area, inclusive ofmicropores, pore diameters less than 2 nm (20 Å). The externalsurface area, based on the statistical thickness method (STSA),is def i ned as the specif i c surface area that is accessible torubber.4.2 CTAB Surface Area (formerly Test Method D3765) hasbeen withdrawn. The CTAB value may be estimated from theSTSA value using Eq 1. The equation is based on a linearregression of the STSAand CTAB measured values of the SRB5 standards.CTAB5 STSA*1.017012.6434 (1)5. Apparatus5.1 Multipoint Static-Volumetric Gas Adsorption Apparatus,with Dewar f l asks and all other accessories required foroperation.5.2 Sample Cells, that when attached to the adsorptionapparatus, will maintain isolation of the sample from theatmosphere equivalent to a helium leak rate of <10 –5 cm 3 /min,per atmosphere of pressure difference.5.3 Balance, Analytical, with 0.1 mg sensitivity.5.4 Heating Mantle or Equivalent, capable of maintaining atemperature of 300 6 10°C.5.5 Oven, Gravity Convection, capable of maintaining atemperature of 125 6 10°C.6. Reagents6.1 Liquid Nitrogen, 98 % or higher purity.1 This test method is under the jurisdiction of ASTM Committee D24 on CarbonBlack and is the direct responsibility of Subcommittee D24.21 on Carbon BlackSurface Area and Related Properties.Current edition approved June 1, 2014. Published July 2014. Originally approvedin 2000. Last previous edition approved in 2010 as D6556 – 10. DOI: 10.1520/D6556-14.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.3 The last approved version of this historical standard is referenced onwww.astm.org.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1