1、Designation: D1218 12Standard 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 revision, the year of la
2、st 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 Department of Defense.1. Scope*1.1 This test method covers the measuremen
3、t 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-mechanical) procedure also coversthe me
4、asurement 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 not apply. Verifica-tion of the a
5、ccuracy 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 colored, or that have bubble
6、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. No other units of measurem
7、ent 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 should be taken when handling
8、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 your state or countrymay be
9、 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 regulatory limitations prior to
10、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 AnalyticalMeasurement System PerformanceD63
11、00 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 and Lubricants, Version4.
12、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, thevalue of the difference thus
13、obtained is usually multiplied by10 000.1This 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 approved Nov. 1, 2012. Published December 2012. Ori
14、ginallyapproved in 1952. Last previous edition approved in 2007 as D121802(2007).DOI: 10.1520/D1218-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards
15、 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 Conshohocken, PA 19428-2959. United States13.1.2 r
16、efractive 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, as light passes from air into the subst
17、ance. 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 variesinversely with both wavelength and
18、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 angle concept.5. Significance and Use5.1
19、 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 Refractometer, high-resolution optical-mechanica
20、l 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 25C,nD= 1.3325; and at 30C, nD= 1.33197.4.3 2,2,4-trimethylpentane, 99 mol % Mi
21、nimum 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 % Minimum Purity, at 20C,nD= 1.4969; at 25C, nD= 1.4941. (Warning2,2,4-trimethylpentane, methylcylcohexane, and toluene are all flam-mable
22、. 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 specifictemperatures are available. The precision of the test me
23、thod (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 ranges andtemperatures.D1218 1228. Sampling8.1 Asamp
24、le 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 followed by filtering or centrifuging toremove the de
25、siccant. 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. Preparation of Apparatus9.1 The refractometer shall be kept
26、 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. Vapors maycause flash fire.) using cotton swabs, fres
27、h 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 the temperatureindicated by the refractometer temperat
28、ure 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 prism temperature can be seriouslyaffected by variations in ambient conditions such as air drafts or changesin room temperature. Reasonabl
29、e 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 drop of 1-bromonaphthalene contact liquid, about 1.5mm i
30、n 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 tocalibrate the instrument using the solid reference sta
31、ndard.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. Calibration of the Refractometer Using LiquidReference Standard
32、s11.1 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 specifiedtest temperature differs by more than 0.0001 of t
33、he 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 desired refractive index rangeand temperature to calibr
34、ate 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 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 assemb
35、ly 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 a light and dark portion. Follow manufacturersinstructions to adjust the instrument so that the boundarybetween the light and dark portions
36、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 the scale. Repeat 12.5 atleast four times, approaching fro
37、m 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 withdifferent wavelength. Determine the refractive index at t
38、hesecondary 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 procedure byanalyzing a quality control (QC) sample, which is sta
39、ble 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 QC/QA protocols established inthe testing facility, Appendix
40、 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 20C or n5895 x.xxxx at 20C (1)where D or the 589 signifies that the
41、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 calculated value and the testtemperature, for example:D1218 123?ng2
42、 nD!?3104at 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 PrecisionRefractive Index:15.1.1 The precision for the manual (optical-mechanical)refractive index procedure, as determined by the statisticalexaminati
43、on 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 sameapparatus, under constant operating conditions, and on identi-cal test m
44、aterial, 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 two, singleand independent results obtained by different operators wo
45、rk-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 (4)15.1.4 The precision of this test method for automatic andmanual
46、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 for refractive dispersion was not ob-tained in accordance with Practic
47、e 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 of displaying the measured refractive index automati-cally and digital
48、ly. 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 measuring device shall be 0.1C or better.16.4 Light SourceFiltered white
49、 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. 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 refractometers are normally cali-brated using liquid reference standards (see 7.4 an
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