1、Designation: D 1218 02 (Reapproved 2007)An American National StandardStandard Test Method forRefractive Index and Refractive Dispersion of HydrocarbonLiquids1This standard is issued under the fixed designation D 1218; the number immediately following the designation indicates the year oforiginal ado
2、ption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1
3、. Scope1.1 This test method covers the measurement of refractiveindex, accurate to four decimal places or better, of transparentand light-colored hydrocarbons in the range of 1.3300 to1.5000 at temperatures from 20 to 30C by manual (optical-mechanical) or automatic (digital) procedure.1.2 The manual
4、 (optical-mechanical) procedure also coversthe measurement of refractive dispersion accurate to the fourthdecimal place or better.NOTE 1The test method may be suitable for measuring the refractiveindices of liquids above 1.5000 and at temperatures both below 20C andabove 30C; however, the test metho
5、d precision may not apply. Verifica-tion of the accuracy of such measurements will depend upon theavailability of reliable, certified reference standards that demonstrate theperformance of the instrument used under the particular measuringconditions.1.3 The test method may not be applicable to liqui
6、ds that arestrongly colored, or that have bubble points so near the testtemperature that a reading cannot be obtained before substan-tial weathering takes place. Liquid color should be limited toNo. 4 ASTM Color or lighter, as determined by Test MethodD 1500.1.4 This standard does not purport to add
7、ress 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:2D 1193 Specif
8、ication for Reagent WaterD 1500 Test Method for ASTM Color of Petroleum Prod-ucts (ASTM Color Scale)D 6299 Practice for Applying Statistical Quality AssuranceTechniques to Evaluate Analytical Measurement SystemPerformanceD 6300 Practice for Determination of Precision and BiasData for Use in Test Met
9、hods for Petroleum Products andLubricantsE1 Specification for ASTM Liquid-in-Glass Thermometers2.2 ASTM Adjuncts:Determination of Precision and Bias Data for Use in TestMethods for Petroleum Products and Lubricants, Version4.0.6533. Terminology3.1 Definitions:3.1.1 refractive dispersionthe differenc
10、e between the re-fractive indexes of a substance for light of two differentwavelengths, both indexes being measured at the same tem-perature. For convenience in calculations, the value of thedifference thus obtained is usually multiplied by 10 000.3.1.2 refractive indexthe ratio of the velocity of l
11、ight (ofspecified wavelength) in air, to its velocity in the substanceunder examination. It may also be defined as the sine of theangle of incidence divided by the sine of the angle ofrefraction, as light passes from air into the substance. This isthe relative index of refraction. If absolute refrac
12、tive index(that is, referred to vacuum) is desired, this value should bemultiplied by the factor 1.00027, the absolute refractive indexof air. The numerical value of refractive index of liquids variesinversely with both wavelength and temperature.4. Summary of Test Method4.1 The refractive index is
13、measured using a high-resolutionrefractometer of an optical-mechanical or automatic digital1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.04.0D on Physical and Chemical Methods.Current edition
14、approved Nov. 1, 2007. Published January 2008. Originallyapproved in 1952. Last previous edition approved in 2002 as D 121802.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information,
15、 refer to the standards Document Summary page onthe ASTM website.3Available from ASTM International Headquarters. Order No. ADJD6300.(Originally published as Lawrey, D. M. G., ed., Calculation of Precision Data:Petroleum Test Methods, ASTM International, 1996.)1Copyright ASTM International, 100 Barr
16、 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.type with the prism temperature accurately controlled. Theinstrument principle is based on the critical angle concept.5. Significance and Use5.1 Refractive index and refractive dispersion are funda-mental physical properties
17、, which can be used in conjunctionwith other properties to characterize pure hydrocarbons andtheir mixtures.PROCEDURE AMANUAL (OPTICAL-MECHANICAL) PROCEDURE6. Apparatus6.1 Refractometer, high-resolution optical-mechanical re-fractometer of the “Abbe” type with suitable measuring range(1.3300 to 1.50
18、00 or higher) and an accuracy/resolution of0.0001 or better refractive index.NOTE 2Prior to 2001, Test Method D 1218 was based on a Bausch at 25C,nD= 1.3325; and at 30C, nD= 1.33197.4.3 2,2,4-trimethylpentane, 99 mol % Minimum Purity,at20C, nD= 1.3915; at 25C, nD= 1.3890.7.4.4 Methylcyclohexane, 99
19、mol % Minimum Purity,at20C, nD= 1.4231; at 25C, nD= 1.4206.7.4.5 Toluene, 99 mol % Minimum Purity, at 20C,nD= 1.4969; at 25C, nD= 1.4941. (Warning2,2,4-trimethylpentane, methylcylcohexane, and toluene are all flam-mable. Their vapor can be harmful.)NOTE 5Other pure materials may be used to calibrate
20、 the instrumentas primary reference material, as long as they can be obtained in 99 mol %minimum purity and accurate values of their refractive indices at specifictemperatures are available. The precision of the test method (see 15.1 and24.1) were obtained using distilled water as the calibrant.7.5
21、Secondary Reference Materials, for calibrating theinstrument.7.5.1 Mineral Oil Calibration Standards, measured andcertified by suppliers for specific refractive index ranges andtemperatures.8. Sampling8.1 Asample of at least 0.5 mLis required. The sample shallbe free of suspended solids, water, or o
22、ther materials that maysettle onto the prism surface and affect the measured reading.Water can be removed from hydrocarbons by treatment withcalcium chloride followed by filtering or centrifuging toremove the desiccant. The possibility of changing the compo-sition of the sample by action of the dryi
23、ng agent, by selectiveadsorption on the filter, or by fractional evaporation, shall beconsidered. (WarningVolatile hydrocarbon samples areflammable.)9. Preparation of Apparatus9.1 The refractometer shall be kept scrupulously clean at alltimes. Dust and oil can impair the optical component of theinst
24、rument. Thoroughly clean the prism faces with toluene,D 1218 02 (2007)2followed by n-pentane (see Note 4)(WarningThese mate-rials are extremely flammable. Harmful if inhaled. Vapors maycause flash fire.) using cotton swabs, fresh clean lens tissue, orsimilar material, in accordance with manufacturer
25、s instruc-tions. Do not dry the prism faces by rubbing with dry cotton.9.2 Adjust the thermostat bath/circulator settings or theelectronic temperature control system so that the temperatureindicated by the refractometer temperature measuring device iswithin 0.1C of the desired value. Turn on the lig
26、ht source andallow the refractometer to equilibrate for 30 min.NOTE 6The constancy of the prism temperature can be seriouslyaffected by variations in ambient conditions such as air drafts or changesin room temperature. Reasonable precautions should be taken to minimizethese factors.10. Calibration o
27、f Refractometer Using Solid ReferenceStandard10.1 Thoroughly clean the prism faces and surfaces of thesolid reference standard (see 7.4.1). Open the prism assembly.Apply a drop of 1-bromonaphthalene contact liquid, about 1.5mm in diameter, to the center of the polished surface of thesolid reference
28、material. Press the reference standard againstthe surface of the prism face with the polished end towards thelight source.10.2 Follow the manufacturers instructions on how tocalibrate the instrument using the solid reference standard.10.3 If the observed refractive index differs from the valueengrav
29、ed on the solid reference standard by more than 0.0001,adjust the refractometers scale reading to match the certifiedvalue, following manufacturers instructions.11. Calibration of the Refractometer Using LiquidReference Standards11.1 Using the procedure described in Section 12, determinethe refracti
30、ve index of any of the Reference Materials specifiedin 7.4 or 7.5 for a specific test temperature. If the observedrefractive index for the chosen reference material at a specifiedtest temperature differs by more than 0.0001 of the listed value,make adjustment to the instrument following manufacturer
31、sinstructions so that the observed refractive index correspondsto the listed value.11.2 For optimum accuracy, use a reference material whoserefractive index is close to the desired refractive index rangeand temperature to calibrate the instrument.12. Procedure12.1 Ensure that the prism faces are cle
32、an and dry. Checkthat the prism temperature is within 0.1C of the desiredtemperature.12.2 Unlock (if necessary) and open the prism assembly.12.3 Place one or two drops of the sample on the lowerprism face. Close the prism assembly and lock (if necessary).Turn on the light source.Allow 3 min temperat
33、ure equilibrationtime.12.4 Look through the eyepiece and observe the fieldconsisting of a light and dark portion. Follow manufacturersinstructions to adjust the instrument so that the boundarybetween the light and dark portions of the field is as sharp aspossible.12.5 Following manufacturers instruc
34、tions, make any ad-ditional adjustment until the sharp boundary line intersects themidpoint of the crosshairs superimposed on the field.12.6 Read the refractive index on the scale. Repeat 12.5 atleast four times, approaching from either side of the sharpboundary line, and average the scale readings.
35、12.7 Record and report the average refractive index value.12.8 If instrument is capable of determining refractivedispersion, change the light source to a light source withdifferent wavelength. Determine the refractive index at thesecondary wavelength following 12.4-12.7.NOTE 7When determining refrac
36、tive dispersion, it is expected that theinstrument would have been calibrated at both wavelengths used.13. Quality Control13.1 Confirm the performance of the test procedure byanalyzing a quality control (QC) sample, which is stable andrepresentative of the sample of interest.13.1.1 When quality cont
37、rol/quality assurance (QC/QA)protocols are established in the testing facility, these may beused to confirm the reliability of the test result.13.1.2 When there are no QC/QA protocols established inthe testing facility, Appendix X4 can be used to provideguidelines in performing this function.14. Cal
38、culation and Report14.1 Report the average refractive index to four decimalplaces and the test temperature at which the test was made, forexample:nD5 x.xxxx at 20C or n5895 x.xxxx at 20C (1)where D or the 589 signifies that the sodium D spectral linewas used.14.2 If a refractive dispersion measureme
39、nt was made,calculate the absolute value of the difference between therefractive indices at the two wavelengths and multiply thedifference by 10 000. Report the calculated value and the testtemperature, for example:? ng2 nD! ? 3 104at t 5 20C (2)where g and D signifies that the mercury g and sodium
40、Dspectral lines were used in the measurement.15. Precision and Bias15.1 PrecisionRefractive Index:15.1.1 The precision for the manual (optical-mechanical)refractive index procedure, as determined by the statisticalexamination of interlaboratory test results conducted in 19964on eight different sampl
41、es from ten laboratories, is as follows:15.1.2 RepeatabilityThe difference between successivetest results, obtained by the same operator with the sameapparatus, under constant operating conditions, and on identi-cal test material, would, in the long run, in the normal and4Supporting data have been f
42、iled at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D02-1493.D 1218 02 (2007)3correct operation of the test method, exceed the followingvalues only in one case in twenty (95 % confidence level):rmanual5 0.0002 (3)15.1.3 ReproducibilityThe difference between t
43、wo, singleand independent results obtained by different operators work-ing in different laboratories on identical test material would, inthe long run, in the normal and correct operation of the testmethod, exceed the following values only in one case in twenty(95 % confidence level):Rmanual5 0.0005
44、(4)15.1.4 The precision of this test method for automatic andmanual refractive index was obtained in accordance withPractice D 6300 using the D02 Precision Program (D2PP)software.315.2 PrecisionRefractive Dispersion:15.2.1 Repeatability = 0.0001215.2.2 Reproducibility = 0.0001215.2.3 The precision f
45、or refractive dispersion was not ob-tained in accordance with Practice D 6300, and was not part ofthe 1996 interlaboratory study.PROCEDURE BAUTOMATIC (DIGITAL)PROCEDURE16. Apparatus16.1 RefractometerAutomatic digital refractometer with asuitable measuring range of 1.3300 to 1.5000 or higher,capable
46、of displaying the measured refractive index automati-cally and digitally. The instrument shall incorporate a solvent-resistant prism seal.16.2 Temperature Control UnitSee 6.2.16.3 Temperature Measuring DeviceA platinum resis-tance probe or equivalent. The accuracy and resolution of thetemperature me
47、asuring device shall be 0.1C or better.16.4 Light SourceFiltered white light such as that ob-tained using a tungsten-halogen lamp or a light emitting diode(LED), capable of providing the sodium D spectral line at 589nm.16.5 Light FiltersSee 6.5.17. Reagents and Materials17.1 See Section 7.18. Sampli
48、ng18.1 See Section 8.19. Preparation of Apparatus19.1 See Section 9. Ensure that the instrument has a solventresistant prism seal.20. Calibration of the Refractometer Using LiquidReference Standards20.1 Automatic digital refractometers are normally cali-brated using liquid reference standards (see 7
49、.4 and 7.5). Theymay require a single, two-point, or multi-point calibration.Follow manufacturers instruction in calibrating the particularautomatic digital refractometer being used.21. Procedure21.1 Ensure that the prism and the surrounding plate anddish/plate (and presser, if fitted) are thoroughly cleaned as in9.1. Ensure the prism temperature is correct and the instrumenthas been properly calibrated.21.2 Introduce the test sample to the prism ensuring that theprism is adequately covered. Do not introduce an excessiveamount because t
