ASTM_D_3238_-_95_2015.pdf

Designation:D323895(Reapproved 2015)Standard Test Method forCalculation of Carbon Distribution and Structural GroupAnalysis of Petroleum Oils by the n-d-M Method1This standard is issued under the fixed designation D3238;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 calculation of the carbondistribution and ring content(Note 1)of olefin-free petroleumoils from measurements of refractive index,density,andmolecular weight(n-d-M).2This test method should not beapplied to oils whose compositions are outside the followingranges:1.1.1 In terms of carbon distributionup to 75%carbonatoms in ring structure;percentage in aromatic rings not largerthan 1.5 times the percentage in naphthenic rings.1.1.2 In terms of ring contentup to four rings per moleculewith not more than half of them aromatic.Acorrection must beapplied for oils containing significant quantities of sulfur.NOTE1The composition of complex petroleum fractions is oftenexpressed in terms of the proportions of aromatic rings(RA),naphthenerings(RN),and paraffin chains(CP)that would comprise a hypotheticalmean molecule.Alternatively,the composition may be expressed in termsof a carbon distribution,that is,the percentage of the total number ofcarbon atoms that are present in aromatic ring structures(%CA),naphthene ring structures(%CN),and paraffin chains(%Cp).1.2 The values stated in SI units are to be regarded as thestandard.The values in parentheses are for information only.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.2.Referenced Documents2.1 ASTM Standards:3D1218 Test Method for Refractive Index and RefractiveDispersion of Hydrocarbon LiquidsD1480 Test Method for Density and Relative Density(Spe-cific Gravity)of Viscous Materials by Bingham Pycnom-eterD1481 Test Method for Density and Relative Density(Spe-cific Gravity)of Viscous Materials by Lipkin BicapillaryPycnometerD1552 Test Method for Sulfur in Petroleum Products byHigh Temperature Combustion and IR DetectionD2502 Test Method for Estimation of Mean Relative Mo-lecular Mass of Petroleum Oils from Viscosity Measure-mentsD2503 Test Method for Relative Molecular Mass(MolecularWeight)of Hydrocarbons by Thermoelectric Measure-ment of Vapor PressureD2622 Test Method for Sulfur in Petroleum Products byWavelength Dispersive X-ray Fluorescence Spectrometry3.Summary of Test Method3.1 The refractive index and density of the oil are deter-mined at 20 C.The molecular weight is determined experi-mentally or estimated from measurements of viscosity at37.8 C and 98.89 C(100 F and 210 F).These data are thenused to calculate the carbon distribution(%CA,%CN,%CP)or the ring analysis(RA,RN)using the appropriate set ofequations.4.Significance and Use4.1 The carbon distribution and ring content serve to ex-press the gross composition of the heavier fractions of petro-leum.These data can be used as an adjunct to the bulkproperties in monitoring the manufacture of lubricating oil basestocks by distillation,solvent refining or hydrogenation,orboth,and in comparing the composition of stocks fromdifferent crude sources.Furthermore,the data can often becorrelated with critical product performance properties.5.Measurement of Physical Properties5.1 Determine the refractive index of the oil at 20 C usingTest Method D1218.5.2 Determine the density at 20 C using Test MethodD1480 or Test Method D1481.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.04.0K on Correlative Methods.Current edition approved Oct.1,2015.Published December 2015.Originallyapproved in 1973.Last previous edition approved in 2010 as D3238 95(2010).DOI:10.1520/D3238-95R15.2Van Nes,K.,and van Westen,H.A.,Aspects of the Constitution of MineralOils,Elsevier,New York,1951.3For 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 States1 5.3 Determine the average molecular weight using TestMethod D2502 or Test Method D2503.6.Determination of Sulfur Content6.1 Determine the percentage of sulfur in the oil using TestMethods D1552 or D2622.7.Calculation of Carbon Distribution and Ring Content7.1 Calculate the factors v and w from the observed density(d)and the observed ref