1、Designation: D1218 12 (Reapproved 2016)Standard Test Method forRefractive Index and Refractive Dispersion of HydrocarbonLiquids1This standard is issued under the fixed designation D1218; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, 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.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method
3、 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 C to 30 C by manual(optical-mechanical) or automatic (digital) procedure.1.2 The manual (optical-mechanical) pro
4、cedure 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 20 C andabove 30 C; however, the test method precision may not app
5、ly. Verifi-cation 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 arestrongly col
6、ored, 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 MethodD1500.1.4 The values stated in SI units are to be regarded asstandard.
7、No other units of measurement are included in thisstandard.1.5 WARNINGMercury has been designated by manyregulatory agencies as a hazardous material that can causecentral nervous system, kidney and liver damage. Mercury, orits vapor, may be hazardous to health and corrosive tomaterials. Caution shou
8、ld be taken when handling mercury andmercury containing products. See the applicable product Ma-terial Safety Data Sheet (MSDS) for details and EPAswebsitehttp:/www.epa.gov/mercury/faq.htmfor addi-tional information. Users should be aware that selling mercuryand/or mercury containing products into y
9、our state or countrymay be prohibited by law.1.6 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 regula
10、tory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1500 Test Method for ASTM Color of Petroleum Products(ASTM Color Scale)D6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasure
11、ment System PerformanceD6300 Practice for Determination of Precision and BiasData for Use in Test Methods 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
12、 and Lubricants, Version4.0.6533. Terminology3.1 Definitions:3.1.1 refractive dispersion, nthe difference between therefractive indices of a substance for light of two differentwavelengths, both indices being measured at the same tem-perature.3.1.1.1 DiscussionFor convenience in calculations, theval
13、ue of the difference thus obtained is usually multiplied by10 000.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.04.0D on Physical and Chemical Methods.Current edition approved O
14、ct. 1, 2016. Published November 2016. Originallyapproved in 1952. Last previous edition approved in 2012 as D1218 12. DOI:10.1520/D1218-12R16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards vol
15、ume information, refer to the standards Document Summary page onthe ASTM website.3Out of print. No longer available from ASTM International Headquarters.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke
16、n, PA 19428-2959. United States13.1.2 refractive index, nthe ratio of the velocity of light(of specified wavelength) in air, to its velocity in the substanceunder examination.3.1.2.1 DiscussionIt may also be defined as the sine of theangle of incidence divided by the sine of the angle ofrefraction,
17、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 value of refractive index of liquids va
18、riesinversely 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 principle is based on the critical a
19、ngle 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.PROCEDURE AMANUAL (OPTICAL-MECHANICAL) PROCEDURE6. Apparatus6.1 Refractom
20、eter, 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 2Prior to 2001, Test Method D1218 was based on a Bausch at 25 C,nD= 1.3325; and at 30 C, nD= 1.3319
21、7.4.3 2,2,4-trimethylpentane, 99 mol % Minimum Purity, at20 C, nD= 1.3915; at 25 C, nD= 1.3890.7.4.4 Methylcyclohexane, 99 mol % Minimum Purity, at20 C, nD= 1.4231; at 25 C, nD= 1.4206.7.4.5 Toluene, 99 mol % Minimum Purity, at 20 C,nD= 1.4969; at 25 C, nD= 1.4941. (Warning2,2,4-trimethylpentane, me
22、thylcylcohexane, 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 mol %minimum purity and accurate values of their refractive indices at specifictemperatu
23、res 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 Calibration Standards, measured andcertified by suppliers for specific refractive index range
24、s andtemperatures.D1218 12 (2016)28. Sampling8.1 Asample of at least 0.5 mLis required.The sample shallbe free of suspended solids, water, or other materials that maysettle onto the prism surface and affect the measured reading.Water can be removed from hydrocarbons by treatment withcalcium chloride
25、 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, shall beconsidered. (WarningVolatile hydrocarbon samples areflammable.)9. Prepa
26、ration 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 Note 4)(WarningThese mate-rials are extremely flammable. Harmful if inhaled.
27、 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.9.2 Adjust the thermostat bath/circulator settings or theelectronic temperature control system so that
28、the temperatureindicated by the refractometer temperature measuring device iswithin 0.1 C of the desired value. Turn on the light 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
29、 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 surfaces of thesolid reference standard (see 7.4.1). Open the prism assembly.Apply a d
30、rop of 1-bromonaphthalene contact liquid, about1.5 mm 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 polished end towards thelight source.10.2 Follow the manufacturers instructions on how t
31、ocalibrate 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 reading to match the certifiedvalue, following manufacturers instructions.11. Calibrat
32、ion 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 temperature. If the observedrefractive index for the chosen reference material at a spe
33、cifiedtest 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 For optimum accuracy, use a reference material whoserefractive index is close to the
34、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 0.1 C of the desiredtemperature.12.2 Unlock (if necessary) and open the prism assembly.12.3 Place one or two drops of t
35、he sample on the lowerprism face. Close the prism assembly and lock (if necessary).Turn on the light source. Allow 3 min temperature equilibra-tion time.12.4 Look through the eyepiece and observe the fieldconsisting of a light and dark portion. Follow manufacturersinstructions to adjust the instrume
36、nt 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 themidpoint of the crosshairs superimposed on the field.12.6 Read the refractive index on
37、 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 of determining refractivedispersion, change the light source to a light source wi
38、thdifferent 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 wavelengths used.13. Quality Control13.1 Confirm the performance of the test proced
39、ure 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 may beused to confirm the reliability of the test result.13.1.2 When there are no Q
40、C/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 the test temperature at which the test was made, forexample:nD5 x.xxxx at 20 C or n
41、5895 x.xxxx at 20 C (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 at the two wavelengths and multiply thedifference by 10 000. Report the calcul
42、ated value and the testtemperature, for example:D1218 12 (2016)3?ng2 nD!?3104at t 5 20 C (2)where g and D signifies that the mercury g and sodium Dspectral lines were used in the measurement.15. Precision and Bias15.1 PrecisionRefractive Index:15.1.1 The precision for the manual (optical-mechanical)
43、refractive index procedure, as determined by the statisticalexamination of interlaboratory test results conducted in 19964on eight different samples from ten laboratories, is as follows:15.1.2 Repeatability The difference between successivetest results, obtained by the same operator with the sameapp
44、aratus, 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):rmanual5 0.0002 (3)15.1.3 Reproducibility The difference between
45、two, 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
46、 (4)15.1.4 The precision of this test method for automatic andmanual refractive index was obtained in accordance withPractice D6300 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
47、or refractive dispersion was not ob-tained in accordance with Practice D6300, 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 o
48、f 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 mea
49、suring device shall be 0.1 C 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 at589 nm.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 has a solventresistant prism seal.20. Calibration of the Refractometer Using LiquidReference Standards20.1 Automatic digital refractome
