1、Designation: D 1218 02An 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 adoption or, in the c
2、ase 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. Scope *1.1 This
3、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 (optical-mechan
4、ical) 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 method precision may
5、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 liquids that arestron
6、gly 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 address all of thes
7、afety 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:D 1193 Specification for Reage
8、nt Water2D 1500 Test Method for ASTM Color of Petroleum Prod-ucts (ASTM Color Scale)3D 6299 Practice for Applying Statistical Quality AssuranceTechniques to Evaluate Analytical Measurement SystemPerformance4D 6300 Practice for the Determination of Precision and BiasData for Use in Test Methods for P
9、etroleum Products andLubricant4E 1 Specification for ASTM Thermometers53. Terminology3.1 Definitions:3.1.1 refractive dispersionthe difference between the re-fractive indexes of a substance for light of two differentwavelengths, both indexes being measured at the same tem-perature. For convenience i
10、n calculations, the value of thedifference thus obtained is usually multiplied by 10 000.3.1.2 refractive indexthe ratio of the velocity of light (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
11、 the sine of the angle ofrefraction, as light passes from air into the substance. This isthe relative index of refraction. If absolute refractive index(that is, referred to vacuum) is desired, this value should bemultiplied by the factor 1.00027, the absolute refractive indexof air. The numerical va
12、lue of refractive index of liquids variesinversely with both wavelength and temperature.4. Summary of Test Method4.1 The refractive index is measured using a high-resolutionrefractometer of an optical-mechanical or automatic digitaltype with the prism temperature accurately controlled. Theinstrument
13、 principle is based on the critical angle concept.5. Significance and Use5.1 Refractive index and refractive dispersion are funda-mental physical properties, which can be used in conjunctionwith other properties to characterize pure hydrocarbons andtheir mixtures.1This test method is under the juris
14、diction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.04 on Hydrocarbon Analysis.Current edition approved June 10, 2002. Published September 2002. Originallypublished as D 121852T. Last previous edition D 121899.2Annual Book of ASTM Sta
15、ndards, Vol 11.01.3Annual Book of ASTM Standards, Vol 05.01.4Annual Book of ASTM Standards, Vol 05.04.5Annual Book of ASTM Standards, Vol 14.03.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1
16、9428-2959, United States.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 1.5000 or higher) and an accuracy/resolution of0.0001 or better refractive index.NOTE 2
17、Prior 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 mol % Minimum Purity,at20C, nD= 1.4231; at 25C, nD= 1.4206.7.4.5 Toluene, 99 mol %
18、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 the instrumentas primary reference material, as long as they can be obtained in 99
19、 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 Secondary Reference Materials, for calibrating theinstrument.7.5.1 Mineral Oil Cali
20、bration Standards, measured andcertified by suppliers for specific refractive index ranges andtemperatures.8. Sampling8.1 A sample of at least 0.5 mL is required. The sample shallbe free of suspended solids, water, or other materials that maysettle onto the prism surface and affect the measured read
21、ing.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 drying agent, by selectiveadsorption on the filter, or by fractional evaporation, sha
22、ll 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 theinstrument. Thoroughly clean the prism faces with toluene,followed by n-pentane (see
23、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 manufacturers instruc-tions. Do not dry the prism faces by rubbing with dry cotton.D12180229.2 Adjust the the
24、rmostat 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 light source andallow the refractometer to equilibrate for 30 min.NOTE 6The constancy of the
25、 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 of Refractometer Using Solid ReferenceStandard10.1 Thoroughly clean the prism faces and su
26、rfaces 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 material. Press the reference standard againstthe surface of the prism face with the poli
27、shed 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 valueengraved on the solid reference standard by more than 0.0001,adjust the refractometers scale re
28、ading to match the certifiedvalue, following manufacturers instructions.11. Calibration of the Refractometer Using LiquidReference Standards11.1 Using the procedure described in Section 12, determinethe refractive index of any of the Reference Materials specifiedin 7.4 or 7.5 for a specific test tem
29、perature. 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 manufacturersinstructions so that the observed refractive index correspondsto the listed value.11.2 F
30、or 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 clean and dry. Checkthat the prism temperature is within 0.1C of the desiredtemperature.12.2
31、 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 temperature equilibrationtime.12.4 Look through the eyepiece and observe the fieldconsisting of
32、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 instructions, make any ad-ditional adjustment until the sharp boundary line intersects themidpo
33、int 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.12.7 Record and report the average refractive index value.12.8 If instrument is capable
34、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 refractive dispersion, it is expected that theinstrument would have been calibrated at both wa
35、velengths 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 control/quality assurance (QC/QA)protocols are established in the testing facility, these ma
36、y 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. Calculation and Report14.1 Report the average refractive index to four decimalplaces and th
37、e 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 measurement was made,calculate the absolute value of the difference between therefractive indices
38、 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 Dspectral lines were used in the measurement.15. Precision and Bias15.1 PrecisionRefract
39、ive 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 19966on eight different samples from ten laboratories, is as follows:15.1.2 RepeatabilityThe difference between succe
40、ssivetest 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 andcorrect operation of the test method, exceed the followingvalues only in one case in twenty (95 % confidence level):
41、rmanual5 0.0002 (3)6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D02-1493.D121802315.1.3 ReproducibilityThe difference between two, singleand independent results obtained by different operators work-ing in different laborator
42、ies 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 (4)15.1.4 The precision of this test method for automatic andmanual refractive index was obtained
43、 in accordance withPractice D 6300 using the D02 Precision Program (D2PP)software.715.2 PrecisionRefractive Dispersion:15.2.1 Repeatability = 0.0001215.2.2 Reproducibility = 0.0001215.2.3 The precision for refractive dispersion was not ob-tained in accordance with Practice D 6300, and was not part o
44、fthe 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 of displaying the measured refractive index automati-cally and digitally. The instrument shall i
45、ncorporate 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 measuring device shall be 0.1C or better.16.4 Light SourceFiltered white light such as that ob-tai
46、ned 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. Sampling18.1 See Section 8.19. Preparation of Apparatus19.1 See Section 9. Ensure that the instrument
47、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 7.4 and 7.5). Theymay require a single, two-point, or multi-point calibration.Follow manufacturer
48、s 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
49、calibrated.21.2 Introduce the test sample to the prism ensuring that theprism is adequately covered. Do not introduce an excessiveamount because this can slow the thermal equilibration. Lowerthe sample presser (if fitted).21.3 Take a succession of readings, noting values, until asteady value is obtained. Record or report, or both, this valueas the refractive index of the sample at the test temperature.NOTE 8From experience using the instrument, the user will be able tojudge with a safe margin the amount of time needed for a sample totherm
