ASTM D1218-02(2007)
(Test Method)Standard Test Method for Refractive Index and Refractive Dispersion of Hydrocarbon Liquids
Standard Test Method for Refractive Index and Refractive Dispersion of Hydrocarbon Liquids
SIGNIFICANCE AND USE
Refractive index and refractive dispersion are fundamental physical properties, which can be used in conjunction with other properties to characterize pure hydrocarbons and their mixtures.
SCOPE
1.1 This test method covers the measurement of refractive index, accurate to four decimal places or better, of transparent and light-colored hydrocarbons in the range of 1.3300 to 1.5000 at temperatures from 20 to 30°C by manual (optical-mechanical) or automatic (digital) procedure.
1.2 The manual (optical-mechanical) procedure also covers the measurement of refractive dispersion accurate to the fourth decimal place or better.
Note 1—The test method may be suitable for measuring the refractive indices of liquids above 1.5000 and at temperatures both below 20°C and above 30°C; however, the test method precision may not apply. Verification of the accuracy of such measurements will depend upon the availability of reliable, certified reference standards that demonstrate the performance of the instrument used under the particular measuring conditions.
1.3 The test method may not be applicable to liquids that are strongly colored, or that have bubble points so near the test temperature that a reading cannot be obtained before substantial weathering takes place. Liquid color should be limited to No. 4 ASTM Color or lighter, as determined by Test Method D 1500.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D1218 − 02(Reapproved 2007)
Standard Test Method for
Refractive Index and Refractive Dispersion of Hydrocarbon
Liquids
This standard is issued under the fixed designation D1218; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript 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 D1500Test Method forASTM Color of Petroleum Products
(ASTM Color Scale)
1.1 This test method covers the measurement of refractive
D6299Practice for Applying Statistical Quality Assurance
index, accurate to four decimal places or better, of transparent
and Control Charting Techniques to Evaluate Analytical
and light-colored hydrocarbons in the range of 1.3300 to
Measurement System Performance
1.5000 at temperatures from 20 to 30°C by manual (optical-
D6300Practice for Determination of Precision and Bias
mechanical) or automatic (digital) procedure.
Data for Use in Test Methods for Petroleum Products and
1.2 The manual (optical-mechanical) procedure also covers
Lubricants
themeasurementofrefractivedispersionaccuratetothefourth
E1Specification for ASTM Liquid-in-Glass Thermometers
decimal place or better.
2.2 ASTM Adjuncts:
NOTE 1—The test method may be suitable for measuring the refractive
Determination of Precision and Bias Data for Use in Test
indices of liquids above 1.5000 and at temperatures both below 20°C and
Methods for Petroleum Products and Lubricants, Version
above 30°C; however, the test method precision may not apply. Verifica-
4.0.65
tion of the accuracy of such measurements will depend upon the
availability of reliable, certified reference standards that demonstrate the
performance of the instrument used under the particular measuring
3. Terminology
conditions.
3.1 Definitions:
1.3 Thetestmethodmaynotbeapplicabletoliquidsthatare
3.1.1 refractive dispersion—the difference between the re-
strongly colored, or that have bubble points so near the test
fractive indexes of a substance for light of two different
temperature that a reading cannot be obtained before substan-
wavelengths, both indexes being measured at the same tem-
tial weathering takes place. Liquid color should be limited to
perature. For convenience in calculations, the value of the
No. 4 ASTM Color or lighter, as determined by Test Method
difference thus obtained is usually multiplied by 10000.
D1500.
3.1.2 refractive index—the ratio of the velocity of light (of
1.4 This standard does not purport to address all of the
specified wavelength) in air, to its velocity in the substance
safety concerns, if any, associated with its use. It is the
under examination. It may also be defined as the sine of the
responsibility of the user of this standard to establish appro-
angle of incidence divided by the sine of the angle of
priate safety and health practices and determine the applica-
refraction, as light passes from air into the substance. This is
bility of regulatory limitations prior to use.
the relative index of refraction. If absolute refractive index
(that is, referred to vacuum) is desired, this value should be
2. Referenced Documents
multiplied by the factor 1.00027, the absolute refractive index
2.1 ASTM Standards:
ofair.Thenumericalvalueofrefractiveindexofliquidsvaries
D1193Specification for Reagent Water inversely with both wavelength and temperature.
4. Summary of Test Method
This test method is under the jurisdiction of ASTM Committee D02 on 4.1 Therefractiveindexismeasuredusingahigh-resolution
PetroleumProductsandLubricantsandisthedirectresponsibilityofSubcommittee
refractometer of an optical-mechanical or automatic digital
D02.04.0D on Physical and Chemical Methods.
type with the prism temperature accurately controlled. The
Current edition approved Nov. 1, 2007. Published January 2008. Originally
instrument principle is based on the critical angle concept.
approved in 1952. Last previous edition approved in 2002 as D1218–02. DOI:
10.1520/D1218-02R07.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from ASTM International Headquarters. Order No. ADJD6300.
Standards volume information, refer to the standard’s Document Summary page on (Originally published as Lawrey, D. M. G., ed., Calculation of Precision Data:
the ASTM website. Petroleum Test Methods, ASTM International, 1996.)
*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 19428-2959. United States
D1218 − 02 (2007)
5. Significance and Use 7. Reagents and Materials
5.1 Refractive index and refractive dispersion are funda- 7.1 n-Pentane, 95 mol % Minimum Purity, for cleaning the
mental physical properties, which can be used in conjunction prism faces. (Warning—Flammable. Harmful if inhaled. Va-
with other properties to characterize pure hydrocarbons and pors may cause flash fire.)
NOTE 4—Low boiling hydrocarbon fractions with boiling range 50 to
their mixtures.
100°C have also been found to be acceptable.
PROCEDURE A—MANUAL (OPTICAL-
7.2 Toluene, HPLC Grade, for cleaning the prism faces.
MECHANICAL) PROCEDURE
(Warning—Flammable. Vapor harmful.)
7.3 1-Bromonaphthalene, 98 mol % Minimum Purity, con-
6. Apparatus
tact liquid when calibrating with solid reference standard.
6.1 Refractometer, high-resolution optical-mechanical re-
(Warning—Toxic when ingested.)
fractometer of the “Abbe” type with suitable measuring range
7.4 Primary Reference Materials, for calibrating the instru-
(1.3300 to 1.5000 or higher) and an accuracy/resolution of
ment.
0.0001 or better refractive index.
7.4.1 Solid Reference Standard, with the value of refractive
NOTE 2—Prior to 2001, Test Method D1218 was based on a Bausch &
index engraved on its upper face.
LombRefractometer.However,thisinstrumentisnolongermanufactured.
7.4.2 Distilled or Deionized Water,conformingtoTypeIIor
Currentlyavailablemanualrefractometersareofthe“Abbe”type(critical
III of Specification D1193. At 20°C, n =1.3330; at 25°C,
D
anglerefractometers,seeX1.2.3).Thereisavarietyofrefractometersthat
n =1.3325; and at 30°C, n =1.3319
have been found to be suitable for this measurement. Some instruments
D D
offer a wider measuring range but it is important to verify the uniformity 7.4.3 2,2,4-trimethylpentane, 99 mol % Minimum Purity, at
of accuracy across the entire measuring range and to ensure suitable
20°C, n =1.3915; at 25°C, n =1.3890.
D D
calibration materials are available for this verification.
7.4.4 Methylcyclohexane, 99 mol % Minimum Purity, at
6.2 Temperature Control Unit, either an external liquid bath
20°C, n =1.4231; at 25°C, n =1.4206.
D D
with both heating and cooling capability and pump for main-
7.4.5 Toluene, 99 mol % Minimum Purity, at 20°C,
taining the indicated prism temperature within 0.1°C, or an
n = 1.4969; at 25°C, n = 1.4941. (Warning—2,2,4-
D D
internal electronic temperature control system (such as Peltier
trimethylpentane,methylcylcohexane,andtolueneareallflam-
system). If an external bath is used, the thermostating liquid
mable. Their vapor can be harmful.)
shallpassthetemperaturemeasuringdeviceonleaving,noton NOTE 5—Other pure materials may be used to calibrate the instrument
asprimaryreferencematerial,aslongastheycanbeobtainedin99mol%
entering the prism. The temperature control unit (external or
minimum purity and accurate values of their refractive indices at specific
internal) shall have the following control specification:
temperatures are available.The precision of the test method (see 15.1 and
Stability ± 0.1°C
24.1) were obtained using distilled water as the calibrant.
Uniformity ± 0.1°C
7.5 Secondary Reference Materials, for calibrating the
Display Resolution 0.1°C or better
instrument.
6.3 Temperature Measuring Device, for those apparatus
7.5.1 Mineral Oil Calibration Standards, measured and
employingmercuryinglassthermometer,ASTMThermometer
certified by suppliers for specific refractive index ranges and
17C having a range from 19 to 27°C, and conforming to the
temperatures.
requirements of Specification E1. For apparatus using non-
mercury in glass thermometer, a platinum resistance probe,
8. Sampling
thermocouple, or equivalent temperature sensors are accept-
8.1 Asampleofatleast0.5mLisrequired.Thesampleshall
able.
be free of suspended solids, water, or other materials that may
6.4 Light Sources—The following type of light source can
settle onto the prism surface and affect the measured reading.
beusedinconjunctionwithanoptical-mechanical(Abbetype)
Water can be removed from hydrocarbons by treatment with
refractometer:
calcium chloride followed by filtering or centrifuging to
6.4.1 Sodium Arc Lamp, Na line at 589 nm.
D
remove the desiccant. The possibility of changing the compo-
6.4.2 Mercury Arc Lamp, Hg line at 546 nm or Hg line at
c g
sition of the sample by action of the drying agent, by selective
436 nm.
adsorption on the filter, or by fractional evaporation, shall be
6.4.3 Cadmium Arc Lamp, Cd line at 644 nm.
C’
considered. (Warning—Volatile hydrocarbon samples are
6.4.4 Mercury-Cadmium Arc Lamp.
flammable.)
6.4.5 Helium Discharge Lamp.
9. Preparation of Apparatus
NOTE 3—Measurement of refractive dispersion requires more than one
type of light source.
9.1 Therefractometershallbekeptscrupulouslycleanatall
6.5 Light Filters—Arc lamps can emit a number of spectral times. Dust and oil can impair the optical component of the
lines that result in multiple-borderlines observed in the refrac- instrument. Thoroughly clean the prism faces with toluene,
tometer. Filters can be used to eliminate unwanted lines followed by n-pentane (see Note 4)(Warning—These mate-
(borderlines). Depending upon instrument design, the manu- rials are extremely flammable. Harmful if inhaled.Vapors may
facturer will recommend and supply a suitable filter or adapt a cause flash fire.) using cotton swabs, fresh clean lens tissue, or
commercially-available filter (for example, interference filter) similar material, in accordance with manufacturer’s instruc-
to suit the application. tions. Do not dry the prism faces by rubbing with dry cotton.
D1218 − 02 (2007)
9.2 Adjust the thermostat bath/circulator settings or the 12.6 Read the refractive index on the scale. Repeat 12.5 at
electronic temperature control system so that the temperature least four times, approaching from either side of the sharp
indicatedbytherefractometertemperaturemeasuringdeviceis boundary line, and average the scale readings.
within 0.1°C of the desired value.Turn on the light source and
12.7 Record and report the average refractive index value.
allow the refractometer to equilibrate for 30 min.
12.8 If instrument is capable of determining refractive
NOTE 6—The constancy of the prism temperature can be seriously
affected by variations in ambient conditions such as air drafts or changes dispersion, change the light source to a light source with
inroomtemperature.Reasonableprecautionsshouldbetakentominimize
different wavelength. Determine the refractive index at the
these factors.
secondary wavelength following 12.4-12.7.
NOTE7—Whendeterminingrefractivedispersion,itisexpectedthatthe
10. Calibration of Refractometer Using Solid Reference
instrument would have been calibrated at both wavelengths used.
Standard
13. Quality Control
10.1 Thoroughly clean the prism faces and surfaces of the
solid reference standard (see 7.4.1). Open the prism assembly.
13.1 Confirm the performance of the test procedure by
Apply a drop of 1-bromonaphthalene contact liquid, about 1.5 analyzing a quality control (QC) sample, which is stable and
mm in diameter, to the center of the polished surface of the
representative of the sample of interest.
solid reference material. Press the reference standard against
13.1.1 When quality control/quality assurance (QC/QA)
thesurfaceoftheprismfacewiththepolishedendtowardsthe
protocols are established in the testing facility, these may be
light source.
used to confirm the reliability of the test result.
13.1.2 When there are no QC/QA protocols established in
10.2 Follow the manufacturer’s instructions on how to
the testing facility, Appendix X4 can be used to provide
calibrate the instrument using the solid reference standard.
guidelines in performing this function.
10.3 If the observed refractive index differs from the value
engraved on the solid reference standard by more than 0.0001,
14. Calculation and Report
adjust the refractometer’s scale reading to match the certified
14.1 Report the average refractive index to four decimal
value, following manufacturer’s instructions.
places and the test temperature at which the test was made, for
example:
11. Calibration of the Refractometer Using Liquid
Reference Standards
n 5 x.xxxxat20°C or n 5 x.xxxxat20°C (1)
D 589
11.1 UsingtheproceduredescribedinSection12,determine
therefractiveindexofanyoftheReferenceMaterialsspecified
where D or the 589 signifies that the sodium D spectral line
in 7.4 or 7.5 for a specific test temperature. If the observed
was used.
refractiveindexforthechosenreferencematerialataspecified
14.2 If a refractive dispersion measurement was made,
testtemperaturediffersbymorethan0.0001ofthelistedvalue,
calculate the absolute value of the difference between the
make adjustment to the instrument following manufacturer’s
refractive indices at the two wavelengths and multiply the
instructions so that the observed refractive index corresponds
difference by 10000. Report the calculated value and the test
to the listed value.
temperature, for example:
11.2 For optimum accuracy, use a reference material whose
n 2 n 310 at t 520°C (2)
~ !
? g D ?
refractive index is close to the desired refractive index range
and temperature to calibrate the instrument.
where g and D signifies that the mercury g and sodium D
12. Procedure
spectral lines were used in the measurement.
12.1 Ensure that the prism faces are clean and dry. Check
15. Precision and Bias
that the prism temperature is within 0.1°C of the desired
15.1 Precision—Refractive Index:
temperature.
15.1.1 The precision for the manual (optical-mechanical)
12.2 Unlock (if necessary) and open the prism assembly.
refractive index procedure, as determined by the statistical
12.3 Place one or two drops of the sample on the lower
examination of interlaboratory test results conducted in 1996
prism face. Close the prism assembly and lock (if necessary).
on eight different samples from ten laboratories, is as follows:
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
AnAmericanNationalStandard Designation: DAn1218American– 02 (ReapprovedNational Standard2007)
Designation:D1218–99
Standard Test Method for
Refractive Index and Refractive Dispersion of Hydrocarbon
Liquids
This standard is issued under the fixed designation D1218; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript 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 *
1.1This test method covers the measurement of refractive indexes, accurate to six units in the fifth decimal place, and refractive
dispersions, accurate to twelve units in the fifth decimal place, of transparent and light-colored hydrocarbon liquids that have
refractive indexes in the range from 1.33 to 1.50, and at temperatures from 20 to 30°C. The test method is not applicable within
theaccuracystatedtoliquidshavingcolorsdarkerthanNo.4ASTMColorasdeterminedbyTestMethodD1500,toliquidshaving
bubble points so near the test temperature that a reading cannot be obtained before substantial weathering takes place, to liquids
having a refractive index above 1.50, or to measurements made at temperatures above 30°C.
1.1 This test method covers the measurement of refractive index, accurate to four decimal places or better, of transparent and
light-colored hydrocarbons in the range of 1.3300 to 1.5000 at temperatures from 20 to 30°C by manual (optical-mechanical) or
automatic (digital) procedure.
1.2 The manual (optical-mechanical) procedure also covers the measurement of refractive dispersion accurate to the fourth
decimal place or better.
NOTE1—The instrument can be successfully used for refractive indexes above 1.50 and at temperatures both below 20°C and above 30°C. As yet,
certified liquid standards for the ranges above a refractive index of 1.50 are not available, so the precision and accuracy of the instrument under these
conditions have not been evaluated. Similarly, certified refractive indexes of liquids at temperatures other than the 20 to 30°C range are not available,
although the instrument can be used up to 50°C.
1.2 1—The test method may be suitable for measuring the refractive indices of liquids above 1.5000 and at temperatures both
below 20°C and above 30°C; however, the test method precision may not apply. Verification of the accuracy of such measurements
will depend upon the availability of reliable, certified reference standards that demonstrate the performance of the instrument used
under the particular measuring conditions.
1.3 The test method may not be applicable to liquids that are strongly colored, or that have bubble points so near the test
temperature that a reading cannot be obtained before substantial weathering takes place. Liquid color should be limited to No. 4
ASTM Color or lighter, as determined by Test Method D1500.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D841Specification for Nitration Grade Toluene 1193 Specification for Reagent Water
D1500 Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
D6299 Practice for Applying Statistical Quality Assurance Techniques to Evaluate Analytical Measurement System
Performance
D6300 Practice for Determination of Precision and Bias Data for Use inTest Methods for Petroleum Products and Lubricants
E1Specification for ASTM Thermometers Specification for ASTM Liquid-in-Glass Thermometers
2.2 ASTM Adjuncts:
This test method is under the jurisdiction ofASTM Committee D-2 on Petroleum Products and Lubricants and is the direct responsibility of Subcommittee D02.04 on
Hydrocarbon Analysis.
Current edition approved Nov. 10, 1999. Published February 2000. Originally published as D1218–52T. Last previous edition D1218–98.
This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products and Lubricants and is the direct responsibility of Subcommittee D02.04.0D
on Physical and Chemical Methods.
Current edition approved Nov. 1, 2007. Published January 2008. Originally approved in 1952. Last previous edition approved in 2002 as D1218–02.
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.For Annual Book of ASTM Standards
, Vol 06.04.volume information, refer to the standard’s Document Summary page on the ASTM website.
*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 19428-2959, United States.
D 1218 – 02 (2007)
Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants, Version 4.0.65
3. Terminology
3.1 Definitions:
3.1.1 refractive index—the ratio of the velocity of light (of specified wavelength) in air, to its velocity in the substance under
examination. It may also be defined as the sine of the angle of incidence divided by the sine of the angle of refraction, as light
passes from air into the substance.This is the relative index of refraction. If absolute refractive index (that is, referred to vacuum)
is desired, this value should be multiplied by the factor 1.00027, the absolute refractive index of air. The numerical value of
refractive index of liquids varies inversely with both wavelength and temperature.
3.1.2refractive dispersion—the difference between the refractive indexes of a substance for light of two different wavelengths,
both indexes being measured at the same temperature. For convenience in calculations, the value of the difference thus obtained
is usually multiplied by 10000.
3.1.2 refractive index—the ratio of the velocity of light (of specified wavelength) in air, to its velocity in the substance under
examination. It may also be defined as the sine of the angle of incidence divided by the sine of the angle of refraction, as light
passes from air into the substance.This is the relative index of refraction. If absolute refractive index (that is, referred to vacuum)
is desired, this value should be multiplied by the factor 1.00027, the absolute refractive index of air. The numerical value of
refractive index of liquids varies inversely with both wavelength and temperature.
4. Summary of Test Method
4.1The refractive index is measured by the critical angle method with a Bausch & Lomb Precision Refractometer (or other
instruments of equivalent or superior performance), using monochromatic light. The instrument is previously adjusted by means
of a solid reference standard and the observed values are corrected, when necessary, by a calibration obtained with certified liquid
standards.
4.1 The refractive index is measured using a high-resolution refractometer of an optical-mechanical or automatic digital type
with the prism temperature accurately controlled. The instrument principle is based on the critical angle concept.
5. Significance and Use
5.1 Refractive index and refractive dispersion are fundamental physical properties thatproperties, which can be used in
conjunction with other properties to characterize pure hydrocarbons and their mixtures.
PROCEDURE A—MANUAL (OPTICAL-MECHANICAL) PROCEDURE
6. Apparatus
6.1 Refractometer,Bausch&Lomb,“Precision”type,range1.33to1.64forthesodium Dline.Otherinstrumentsofequivalent
or superior performance, such as automatic refractometers, shall meet the precision section requirements as minimum criteria. ,
high-resolution optical-mechanical refractometer of the “Abbe” type with suitable measuring range (1.3300 to 1.5000 or higher)
and an accuracy/resolution of 0.0001 or better refractive index.
NOTE2—When other instruments are used, follow the manufacturer’s instruction for operation and maintenance. Section 12 shall strictly be adhered
to on any instrument used, except that Sections 11 and 13 may be substituted with the appropriate manufacturer’s instructions.
6.2Thermostat and Circulating Pump, capable of maintaining the indicated prism temperature constant within 0.02°C of the
desired test temperature. The thermostating liquid should pass the thermometer on leaving, not on entering, the prism assembly.
NOTE3—In the Bausch & Lomb refractometer, the thermostating liquid shall pass the thermometer on leaving, not on entering the prism assembly.
6.3Thermometer—ASTM Saybolt Viscosity Thermometer 17C having a range from 19 to 27°C, and conforming to the
requirements of Specification E1.The thermometer shall be used in an approved holder, as shown in Fig. 1, such that almost total
immersion (not more than emergent stem) is obtained, and reading to 0.01°C is possible.
NOTE4—Other temperature sensing devices, such as thermocouples, that can provide equivalent or better temperature control may be used in place of
the thermometer specified in 6.3.
6.4 2—Prior to 2001, Test Method D 1218 was based on a Bausch & Lomb Refractometer. However, this instrument is no longer
manufactured. Currently available manual refractometers are of the “Abbe” type (critical angle refractometers, see X1.2.3). There
is a variety of refractometers that have been found to be suitable for this measurement. Some instruments offer a wider measuring
range but it is important to verify the uniformity of accuracy across the entire measuring range and to ensure suitable calibration
materials are available for this verification.
Annual Book of ASTM Standards, Vol 05.01.
AvailablefromASTMInternationalHeadquarters.OrderNo.ADJD6300.(OriginallypublishedasLawrey,D.M.G.,ed., Calculation of Precision Data: Petroleum Test
Methods, ASTM International, 1996.)
D 1218 – 02 (2007)
6.2 Temperature Control Unit,eitheranexternalliquidbathwithbothheatingandcoolingcapabilityandpumpformaintaining
the indicated prism temperature within 0.1°C, or an internal electronic temperature control system (such as Peltier system). If an
external bath is used, the thermostating liquid shall pass the temperature measuring device on leaving, not on entering the prism.
The temperature control unit (external or internal) shall have the following control specification:
Stability 6 0.1°C
Uniformity 6 0.1°C
Display Resolution 0.1°C or better
6.3 Temperature Measuring Device , for those apparatus employing mercury in glass thermometer, ASTM Thermometer 17C
havingarangefrom19to27°C,andconformingtotherequirementsofSpecificationE1.Forapparatususingnon-mercuryinglass
thermometer, a platinum resistance probe, thermocouple, or equivalent temperature sensors are acceptable.
6.4 Light Sources—Thefollowinglightsourceshavebeenfoundsatisfactory:—Thefollowingtypeoflightsourcecanbeused
in conjunction with an optical-mechanical (Abbe type) refractometer:
6.4.1 Sodium Arc Lamp—The Unitized “Sodium Lab Arc” is furnished with the instrument. , Na line at 589 nm.
D
6.4.2 Mercury Arc Lamp—The H-4 type capillary mercury arc is furnished as an accessory to the refractometer.
6.4.3Hydrogen Discharge Lamp—Any type of lamp capable of producing light having an intensity of at least 32 lx (3
footcandles) on an area of 1 cm on the entrance face of the illuminating prism. The luminous intensity may be conveniently
measured by means of a photographic light meter held 254 mm (10 in.) from the lamp and perpendicular to the light beam. For
convenience, the lamp should be mounted on an extension of the sodium lamp support. , Hg line at 546 nm or Hg line at 436
c g
nm.
6.4.3 Cadmium Arc Lamp,Cd line at 644 nm.
C’
6.4.4 Other Sources—Helium may be used in place of hydrogen in the lamp discussed in 6.4.3Mercury-CadmiumArc Lamp.
6.4.5 Light Filters—For isolating the various spectral lines from the above sources, special light filters are required. The
following are tentatively recommended:
˚
Wave-length, A Spectral Line Filter
6678 Helium Corning No. 2404
6563 H None required. May use Corning No. 2404.
c
5893 Na None required
D
5461 Hg Wratten No. 62, or No. 77A, Corning Nos.
c
3486+4303+5120
5016 Helium Wratten No. 45
4861 H Corning Nos. 5030+3387, 4303, or Wratten
F
No. 45
4358 Hg Corning Nos. 5113, 3389+5850.
g
Helium Discharge Lamp.
NOTE5—Indeterminationsofrefractiveindexesaboveapproximately1.53(wherevertheshortwavelengthsshowahigherscalereadingthanthelong),
thissystemoffiltersisrenderedworthless,andfiltersmustbechosenthatremoveallspectrallinesofshorterwavelengththantheonebeingread.Below
this refractive index, the specific filters listed above, which remove spectral lines of longer wavelengths than the one being read, should be used.
3—Measurement of refractive dispersion requires more than one type of light source.
6.5 Light Filters—Arc lamps can emit a number of spectral lines that result in multiple-borderlines observed in the
refractometer. Filters can be used to eliminate unwanted lines (borderlines). Depending upon instrument design, the manufacturer
will recommend and supply a suitable filter or adapt a commercially-available filter (for example, interference filter) to suit the
application.
7. Solvents Reagents and Materials
7.1 n-Pentane, 95 mol% minimum purity. (Warning—Extremely flammable. Harmful if inhaled.Vapors may cause flash fire.)
n-Pentane, 95 mol% Minimum Purity, for cleaning the prism faces. (Warning—Flammable. Harmful if inhaled. Vapors may
cause flash fire.)
NOTE 4—Low boiling hydrocarbon fractions with boiling range 50 to 100°C have also been found to be acceptable.
7.2 Toluene, conforming to Specification D841. (Warning—Toluene, HPLC Grade, for cleaning the prism faces. (Warning—
Flammable. Vapor harmful.)
8.Reference Standards
8.1
7.3 1-Bromonaphthalene, 98 mol % Minimum Purity, contact liquid when calibrating with solid reference standard.
(Warning—Toxic when ingested.)
7.4 Primary Reference Materials , for calibrating the instrument.
7.4.1 Solid Reference Standard, accurate to 60.00002 with the value of the refractive index engraved upon its upper face.
8.2Primary Liquid Standards—The organic liquids listed below, with the values of their refractive indexes for the D, F, and C
lines certified at 20, 25, and 30°C, obtained from the API Standard Reference Office: (Warning—Flammable.)
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