ASTM D1298-12b(2017)
(Test Method)Standard Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method
Standard Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method
SIGNIFICANCE AND USE
5.1 Accurate determination of the density, relative density (specific gravity), or API gravity of petroleum and its products is necessary for the conversion of measured volumes to volumes or masses, or both, at the standard reference temperatures of 15 °C or 60 °F during custody transfer.
5.2 This procedure is most suitable for determining the density, relative density (specific gravity), or API gravity of low viscosity transparent liquids. This procedure can also be used for viscous liquids by allowing sufficient time for the hydrometer to reach temperature equilibrium, and for opaque liquids by employing a suitable meniscus correction. Additionally for both transparent and opaque fluids the readings shall be corrected for the thermal glass expansion effect and alternative calibration temperature effects before correcting to the reference temperature.
5.3 When used in connection with bulk oil measurements, volume correction errors are minimized by observing the hydrometer reading at a temperature close to that of the bulk oil temperature.
5.4 Density, relative density, or API gravity is a factor governing the quality and pricing of crude petroleum. However, this property of petroleum is an uncertain indication of its quality unless correlated with other properties.
5.5 Density is an important quality indicator for automotive, aviation and marine fuels, where it affects storage, handling and combustion.
SCOPE
1.1 This test method covers the laboratory determination using a glass hydrometer in conjunction with a series of calculations, of the density, relative density, or API gravity of crude petroleum, petroleum products, or mixtures of petroleum and nonpetroleum products normally handled as liquids, and having a Reid vapor pressure of 101.325 kPa (14.696 psi) or less. Values are determined at existing temperatures and corrected to 15 °C or 60 °F by means of a series of calculations and international standard tables.
1.2 The initial hydrometer readings obtained are uncorrected hydrometer readings and not density measurements. Readings are measured on a hydrometer at either the reference temperature or at another convenient temperature, and readings are corrected for the meniscus effect, the thermal glass expansion effect, alternative calibration temperature effects and to the reference temperature by means of the Petroleum Measurement Tables; values obtained at other than the reference temperature being hydrometer readings and not density measurements.
1.3 Readings determined as density, relative density, or API gravity can be converted to equivalent values in the other units or alternative reference temperatures by means of Interconversion Procedures (API MPMS Chapter 11.5), or Adjunct to D1250 Guide for Petroleum Measurement Tables (API MPMS Chapter 11.1), or both, or tables, as applicable.
1.4 The initial hydrometer readings determined in the laboratory shall be recorded before performing any calculations. The calculations required in Section 10 shall be applied to the initial hydrometer reading with observations and results reported as required by Section 11 prior to use in a subsequent calculation procedure (ticket calculation, meter factor calculation, or base prover volume determination).
1.5 Annex A1 contains a procedure for verifying or certifying the equipment for this test method.
1.6 The values stated in SI units are to be regarded as standard.
1.6.1 Exception—The values given in parentheses are provided for information only.
1.7 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.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in th...
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Designation: D1298 − 12b (Reapproved 2017)
Manual of Petroleum Measurement Standards (MPMS), Chapter 9.1
Standard Test Method for
Density, Relative Density, or API Gravity of Crude Petroleum
and Liquid Petroleum Products by Hydrometer Method
This standard is issued under the fixed designation D1298; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number 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 U.S. Department of Defense.
1. Scope initial hydrometer reading with observations and results re-
ported as required by Section 11 prior to use in a subsequent
1.1 This test method covers the laboratory determination
calculation procedure (ticket calculation, meter factor
using a glass hydrometer in conjunction with a series of
calculation, or base prover volume determination).
calculations, of the density, relative density, or API gravity of
crude petroleum, petroleum products, or mixtures of petroleum 1.5 Annex A1 contains a procedure for verifying or certify-
and nonpetroleum products normally handled as liquids, and ing the equipment for this test method.
having a Reid vapor pressure of 101.325 kPa (14.696 psi) or
1.6 The values stated in SI units are to be regarded as
less. Values are determined at existing temperatures and
standard.
corrected to 15 °C or 60 °F by means of a series of calculations
1.6.1 Exception—The values given in parentheses are pro-
and international standard tables.
vided for information only.
1.2 The initial hydrometer readings obtained are uncor-
1.7 This standard does not purport to address all of the
rected hydrometer readings and not density measurements.
safety concerns, if any, associated with its use. It is the
Readings are measured on a hydrometer at either the reference
responsibility of the user of this standard to establish appro-
temperature or at another convenient temperature, and readings
priate safety and health practices and determine the applica-
are corrected for the meniscus effect, the thermal glass expan-
bility of regulatory limitations prior to use.
sion effect, alternative calibration temperature effects and to the
1.8 This international standard was developed in accor-
reference temperature by means of the Petroleum Measurement
dance with internationally recognized principles on standard-
Tables; values obtained at other than the reference temperature
ization established in the Decision on Principles for the
being hydrometer readings and not density measurements.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.3 Readings determined as density, relative density, or API
Barriers to Trade (TBT) Committee.
gravity can be converted to equivalent values in the other units
or alternative reference temperatures by means of Interconver-
2. Referenced Documents
sion Procedures (API MPMS Chapter 11.5), or Adjunct to
D1250 Guide for Petroleum Measurement Tables (API MPMS
2.1 ASTM Standards:
Chapter 11.1), or both, or tables, as applicable.
D1250 Guide for Use of the Petroleum Measurement Tables
D4057 Practice for Manual Sampling of Petroleum and
1.4 The initial hydrometer readings determined in the labo-
Petroleum Products
ratory shall be recorded before performing any calculations.
D4177 Practice for Automatic Sampling of Petroleum and
The calculations required in Section 10 shall be applied to the
Petroleum Products
D5854 Practice for Mixing and Handling of Liquid Samples
of Petroleum and Petroleum Products
This test method is under the jurisdiction of ASTM Committee D02 on
E1 Specification for ASTM Liquid-in-Glass Thermometers
Petroleum Products, Liquid Fuels, and Lubricants and the API Committee on
Petroleum Measurement, and is the direct responsibility of Subcommittee D02.02 E100 Specification for ASTM Hydrometers
/COMQ, the joint ASTM-API Committee on Hydrocarbon Measurement for
Custody Transfer (Joint ASTM-API). This test method has been approved by the
sponsoring committees and accepted by the Cooperating Societies in accordance
with established procedures. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 15, 2017. Published July 2017. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1953. Last previous edition approved in 2012 as D1298 – 12b. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D1298-12BR17. the ASTM website.
© Jointly copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, USA and the American Petroleum Institute (API), 1220 L Street NW, Washington DC 20005, USA
D1298 − 12b (2017)
2.2 API Standards: Reading – Observed). For nontransparent fluids the point at
MPMS Chapter 8.1 Manual Sampling of Petroleum and which the liquid surface cuts the Hydrometer scale cannot be
Petroleum Products (ASTM Practice D4057) determined directly and requires a correction (Meniscus Cor-
MPMS Chapter 8.2 Automatic Sampling of Petroleum and rection). The value represented by the point (Meniscus Read-
Petroleum Products (ASTM Practice D4177) ing) at which the liquid sample rises above the main surface of
MPMS Chapter 8.3 Mixing and Handling of Liquid Samples the liquid subtracted from the value represented by where the
of Petroleum and Petroleum Products (ASTM Practice main surface of the liquid cuts the Hydrometer scale is the
D5854) amount of the correction or Meniscus correction. This menis-
MPMS Chapter 11.1 Temperature and Pressure Volume Cor- cus correction is documented and then subtracted from the
rection Factors for Generalized Crude Oils, Refined Prod- value represented by the Meniscus Reading to yield the
ucts and Lubricating Oils (Adjunct to ASTM D1250) Hydrometer Reading corrected for the Meniscus (Hydrometer
MPMS Chapter 11.5 Density/Weight/Volume Intraconver- Reading – Observed, Meniscus Corrected).
sion
3.1.5 observed values, n—values observed at temperatures
2.3 Energy Institute Standards:
other than the specified reference temperature. These values are
IP 389 Determination of wax appearance temperature
only hydrometer readings and not density, relative density
(WAT) of middle distillate fuels by differential thermal
(specific gravity), or API gravity at that other temperature.
analysis (DTA) or differential scanning calorimetry (DSC)
3.1.6 pour point, n—lowest temperature at which a test
IP Standard Methods Book, Appendix A, Specifications – IP
portion of crude petroleum or petroleum product will continue
Standard Thermometers
to flow when it is cooled under specified conditions.
2.4 ISO Standards:
3.1.7 relative density (specific gravity), n—the ratio of the
ISO 649-1 Laboratory glassware – Density hydrometers for
mass of a given volume of liquid at a specific temperature to
general purpose – Part 1: Specification
the mass of an equal volume of pure water at the same or
2.5 ASTM Adjuncts:
different temperature. Both reference temperatures shall be
Adjunct to D1250 Guide for Petroleum Measurement Tables
explicitly stated.
(API MPMS Chapter 11.1)
3.1.7.1 Discussion—Common reference temperatures in-
3. Terminology
clude 60/60 °F, 20 ⁄20 °C, 20/4 °C. The historic deprecated
term specific gravity may still be found.
3.1 Definitions of Terms Specific to This Standard:
3.1.1 API gravity, n—a special function of relative density 3.1.8 wax appearance temperature (WAT), n—temperature
at which waxy solids form when a crude petroleum or
(specific gravity) 60/60 °F, represented by:
petroleum product is cooled under specified conditions.
°API5 141.5/ relative density 60/60 °F 2 131.5 (1)
@ ~ !#
3.1.1.1 Discussion—No statement of reference temperature
4. Summary of Test Method
is required, as 60 °F is included in the definition.
4.1 The sample is brought to a specified temperature and a
3.1.2 cloud point, n—temperature at which a cloud of wax
test portion is transferred to a hydrometer cylinder that has
crystals first appears in a liquid when it is cooled under specific
been brought to approximately the same temperature. The
conditions.
appropriate hydrometer and thermometer, also at a similar
3.1.3 density, n—the mass of liquid per unit volume at 15 °C
temperature, are lowered into the test portion and allowed to
and 101.325 kPa with the standard unit of measurement being
settle. After temperature equilibrium has been reached, the
kilograms per cubic metre.
hydrometer scale is read, and the temperature of the test
3.1.3.1 Discussion—Other reference temperatures, such as
portion is taken. The observed hydrometer reading is corrected
20 °C, may be used for some products or in some locations.
for the meniscus effect, the thermal glass expansion effect,
Less preferred units of measurement (for example, kg/L or
alternative calibration temperature effects and then reduced to
g/mL) are still in use.
the reference temperature by means of the volume correction
3.1.4 hydrometer reading, n—the point on the hydrometer
factors or tables as applicable by use of the appropriate Adjunct
scale at which the surface of the liquid cuts the scale.
to D1250 Guide for Petroleum Measurement Tables (API
3.1.4.1 Discussion—In practice for transparent fluids this
MPMS Chapter 11.1) and observed temperature from the
can be readily determined by aligning the surface of the liquid
thermometer.
on both sides of the hydrometer and reading the Hydrometer
4.2 If necessary, the hydrometer cylinder and its contents
scale where these surface readings cut the scale (Hydrometer
are placed in a constant temperature bath to avoid excessive
temperature variation during the test.
Published as Manual of Petroleum Measurement Standards. Available from the
American Petroleum Institute (API), 1220 L St., NW, Washington, DC 20005-4070,
5. Significance and Use
http://www.api.org.
5.1 Accurate determination of the density, relative density
Available from Energy Institute, 61 New Cavendish St., London, W1G 7AR,
U.K., http://www.energyinst.org.
(specific gravity), or API gravity of petroleum and its products
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
is necessary for the conversion of measured volumes to
4th Floor, New York, NY 10036, http://www.ansi.org.
6 volumes or masses, or both, at the standard reference tempera-
Available from ASTM International Headquarters. Order Adjunct No.
ADJD1250. Original adjunct produced in 1983. tures of 15 °C or 60 °F during custody transfer.
D1298 − 12b (2017)
TABLE 2 Recommended Thermometers
5.2 This procedure is most suitable for determining the
density, relative density (specific gravity), or API gravity of Scale Range Graduation Interval Scale Error
low viscosity transparent liquids. This procedure can also be °C −1 – +38 0.1 ± 0.1
°C −20 – +102 0.2 ± 0.15
used for viscous liquids by allowing sufficient time for the
°F −5 – +215 0.5 ± 0.25
hydrometer to reach temperature equilibrium, and for opaque
liquids by employing a suitable meniscus correction. Addition-
ally for both transparent and opaque fluids the readings shall be
repeatability and reproducibility values are not applicable if
corrected for the thermal glass expansion effect and alternative
alternative fluids are used in the liquid-in-glass thermometers.
calibration temperature effects before correcting to the refer-
ence temperature.
6.3 Hydrometer Cylinder, clear glass, or plastic (see 6.3.1).
The inside diameter of the cylinder shall be at least 25 mm
5.3 When used in connection with bulk oil measurements,
greater than the outside diameter of the hydrometer and the
volume correction errors are minimized by observing the
height shall be such that the appropriate hydrometer floats in
hydrometer reading at a temperature close to that of the bulk oil
the sample test portion with at least 25 mm clearance between
temperature.
the bottom of the hydrometer and the bottom of the cylinder.
5.4 Density, relative density, or API gravity is a factor
6.3.1 Hydrometer cylinders constructed of plastic materials
governing the quality and pricing of crude petroleum.
shall be resistant to discoloration or attack by oil samples and
However, this property of petroleum is an uncertain indication
shall not affect the material being tested. They shall not become
of its quality unless correlated with other properties.
opaque under prolonged exposure to sunlight.
5.5 Density is an important quality indicator for automotive,
6.4 Constant-Temperature Bath, if required, of dimensions
aviation and marine fuels, where it affects storage, handling
such that it can accommodate the hydrometer cylinder with the
and combustion.
test portion fully immersed below the test portion liquid
surface, and a temperature control system capable of maintain-
6. Apparatus
ing the bath temperature within 0.25 °C of the test temperature
6.1 Hydrometers, of glass, graduated in units of density,
throughout the duration of the test.
relative density, or API gravity as required, conforming to
6.5 Stirring Rod, optional, of glass or plastic, approximately
Specification E100 or ISO 649-1, and the requirements given
400 mm in length.
in Table 1.
6.1.1 The user should ascertain that the instruments used for
7. Sampling
this procedure conform to the requirements set out above with
7.1 Unless otherwise specified, samples of non-volatile
respect to materials, dimensions, and scale errors. In cases
petroleum and petroleum products shall be taken by the
where the instrument is provided with a calibration certificate
procedures described in Practice D4057 (API MPMS Chapter
issued by a recognized standardizing body, the instrument is
8.1) and D4177 (API MPMS Chapter 8.2).
classed as certified and the appropriate corrections for the
meniscus effect, the thermal glass expansion effect, and alter-
7.2 Samples of volatile crude petroleum or petroleum prod-
native calibration temperature effects shall be applied to the
ucts are preferably taken by Practice D4177 (API MPMS
observed readings prior to corrections. Instruments that satisfy
Chapter 8.2), using a variable volume (floating piston) sample
the requirements of this test method, but are not provided with
receiver to minimize any loss of light components which may
a recognized calibration certificate, are classed as uncertified.
affect the accuracy of the density measurement. In the absence
of this facility, extreme care shall be taken to minimize these
6.2 Thermometers, having range, g
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM 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.
Designation: D1298 − 12b D1298 − 12b (Reapproved 2017)
Manual of Petroleum Measurement Standards (MPMS), Chapter 9.1
Standard Test Method for
Density, Relative Density, or API Gravity of Crude Petroleum
and Liquid Petroleum Products by Hydrometer Method
This standard is issued under the fixed designation D1298; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number 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 U.S. Department of Defense.
1. Scope*Scope
1.1 This test method covers the laboratory determination using a glass hydrometer in conjunction with a series of calculations,
of the density, relative density, or API gravity of crude petroleum, petroleum products, or mixtures of petroleum and nonpetroleum
products normally handled as liquids, and having a Reid vapor pressure of 101.325 kPa (14.696 psi) 101.325 kPa (14.696 psi) or
less. Values are determined at existing temperatures and corrected to 15°C15 °C or 60°F60 °F by means of a series of calculations
and international standard tables.
1.2 The initial hydrometer readings obtained are uncorrected hydrometer readings and not density measurements. Readings are
measured on a hydrometer at either the reference temperature or at another convenient temperature, and readings are corrected for
the meniscus effect, the thermal glass expansion effect, alternatealternative calibration temperature effects and to the reference
temperature by means of the Petroleum Measurement Tables; values obtained at other than the reference temperature being
hydrometer readings and not density measurements.
1.3 Readings determined as density, relative density, or API gravity can be converted to equivalent values in the other units or
alternatealternative reference temperatures by means of Interconversion Procedures (API MPMS Chapter 11.5), or Adjunct to
D1250 Guide for Petroleum Measurement Tables (API MPMS Chapter 11.1), or both, or tables, as applicable.
1.4 The initial hydrometer readings determined in the laboratory shall be recorded before performing any calculations. The
calculations required in Section 10 shall be applied to the initial hydrometer reading with observations and results reported as
required by Section 11 prior to use in a subsequent calculation procedure (ticket calculation, meter factor calculation, or base
prover volume determination).
1.5 Annex A1 contains a procedure for verifying or certifying the equipment for this test method.
1.6 The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for information
only.
1.6.1 Exception—The values given in parentheses are provided for information only.
1.7 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.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1250 Guide for Use of the Petroleum Measurement Tables
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and the API Committee on Petroleum
Measurement, and is the direct responsibility of Subcommittee D02.02 /COMQ, the joint ASTM-API Committee on Hydrocarbon Measurement for Custody Transfer (Joint
ASTM-API). This test method has been approved by the sponsoring committees and accepted by the Cooperating Societies in accordance with established procedures.
Current edition approved June 1, 2012July 15, 2017. Published October 2012July 2017. Originally approved in 1953. Last previous edition approved in 2012 as
D1298D1298 – 12b.–12a. DOI: 10.1520/D1298-12B.10.1520/D1298-12BR17.
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 Standards
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
© Jointly copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, USA and the American Petroleum Institute (API), 1220 L Street NW, Washington DC 20005, USA
D1298 − 12b (2017)
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products
E1 Specification for ASTM Liquid-in-Glass Thermometers
E100 Specification for ASTM Hydrometers
2.2 API Standards:
MPMS Chapter 8.1 Manual Sampling of Petroleum and Petroleum Products (ASTM Practice D4057)
MPMS Chapter 8.2 Automatic Sampling of Petroleum and Petroleum Products (ASTM Practice D4177)
MPMS Chapter 8.3 Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products (ASTM Practice D5854)
MPMS Chapter 11.1 Temperature and Pressure Volume Correction Factors for Generalized Crude Oils, Refined Products and
Lubricating Oils (Adjunct to ASTM D1250)
MPMS Chapter 11.5 Density/Weight/Volume Intraconversion
2.3 Energy Institute Standards:
IP 389 Determination of wax appearance temperature (WAT) of middle distillate fuels by differential thermal analysis (DTA) or
differential scanning calorimetry (DSC)
IP Standard Methods Book, Appendix A, Specifications – IP Standard Thermometers
2.4 ISO Standards:
ISO 649-1 Laboratory glassware – Density hydrometers for general purpose – Part 1: Specification
2.5 ASTM Adjuncts:
Adjunct to D1250 Guide for Petroleum Measurement Tables (API MPMS Chapter 11.1)
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 API gravity, n—a special function of relative density (specific gravity) 60/60°F,60/60 °F, represented by:
°API 5 141.5/ relative density 60/60 °F 2 131.5 (1)
@ ~ !#
Published as Manual of Petroleum Measurement Standards. Available from the American Petroleum Institute (API), 1220 L St., NW, Washington, DC 20005. 20005-4070,
http://www.api.org.
Available from Energy Institute, 61 New Cavendish St., London, W1M 8AR, UK.W1G 7AR, U.K., http://www.energyinst.org.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.10036, http://www.ansi.org.
Available from ASTM International Headquarters. Order Adjunct No. ADJD1250. Original adjunct produced in 1983.
3.1.1.1 Discussion—
No statement of reference temperature is required, as 60°F60 °F is included in the definition.
3.1.2 cloud point, n—temperature at which a cloud of wax crystals first appears in a liquid when it is cooled under specific
conditions.
3.1.3 density, n—the mass of liquid per unit volume at 15°C15 °C and 101.325 kPa 101.325 kPa with the standard unit of
measurement being kilograms per cubic metre.
3.1.3.1 Discussion—
Other reference temperatures, such as 20°C,20 °C, may be used for some products or in some locations. Less preferred units of
measurement (for example, kg/L or g/mL) are still in use.
3.1.4 hydrometer reading, n—the point on the hydrometer scale at which the surface of the liquid cuts the scale.
3.1.4.1 Discussion—
In practice for transparent fluids this can be readily determined by aligning the surface of the liquid on both sides of the hydrometer
and reading the Hydrometer scale where these surface readings cut the scale (Hydrometer Reading – Observed). For nontransparent
fluids the point at which the liquid surface cuts the Hydrometer scale cannot be determined directly and requires a correction
(Meniscus Correction). The value represented by the point (Meniscus Reading) at which the liquid sample rises above the main
surface of the liquid subtracted from the value represented by where the main surface of the liquid cuts the Hydrometer scale is
the amount of the correction or Meniscus correction. This meniscus correction is documented and then subtracted from the value
represented by the Meniscus Reading to yield the Hydrometer Reading corrected for the Meniscus (Hydrometer Reading –
Observed, Meniscus Corrected).
D1298 − 12b (2017)
3.1.5 observed values, n—values observed at temperatures other than the specified reference temperature. These values are only
hydrometer readings and not density, relative density (specific gravity), or API gravity at that other temperature.
3.1.6 pour point, n—lowest temperature at which a test portion of crude petroleum or petroleum product will continue to flow
when it is cooled under specified conditions.
3.1.7 relative density (specific gravity), n—the ratio of the mass of a given volume of liquid at a specific temperature to the mass
of an equal volume of pure water at the same or different temperature. Both reference temperatures shall be explicitly stated.
3.1.7.1 Discussion—
Common reference temperatures include 60/60°F, 20/20°C,60/60 °F, 20 20/4°C.⁄20 °C, 20/4 °C. The historic deprecated term
specific gravity may still be found.
3.1.8 wax appearance temperature (WAT), n—temperature at which waxy solids form when a crude petroleum or petroleum
product is cooled under specified conditions.
4. Summary of Test Method
4.1 The sample is brought to a specified temperature and a test portion is transferred to a hydrometer cylinder that has been
brought to approximately the same temperature. The appropriate hydrometer and thermometer, also at a similar temperature, are
lowered into the test portion and allowed to settle. After temperature equilibrium has been reached, the hydrometer scale is read,
and the temperature of the test portion is taken. The observed hydrometer reading is corrected for the meniscus effect, the thermal
glass expansion effect, alternatealternative calibration temperature effects and then reduced to the reference temperature by means
of the volume correction factors or tables as applicable by use of the appropriate Adjunct to D1250 Guide for Petroleum
Measurement Tables (API MPMS Chapter 11.1) and observed temperature from the thermometer.
4.2 If necessary, the hydrometer cylinder and its contents are placed in a constant temperature bath to avoid excessive
temperature variation during the test.
5. Significance and Use
5.1 Accurate determination of the density, relative density (specific gravity), or API gravity of petroleum and its products is
necessary for the conversion of measured volumes to volumes or masses, or both, at the standard reference temperatures of
15°C15 °C or 60°F60 °F during custody transfer.
5.2 This procedure is most suitable for determining the density, relative density (specific gravity), or API gravity of low
viscosity transparent liquids. This procedure can also be used for viscous liquids by allowing sufficient time for the hydrometer
to reach temperature equilibrium, and for opaque liquids by employing a suitable meniscus correction. Additionally for both
transparent and opaque fluids the readings shall be corrected for the thermal glass expansion effect and alternatealternative
calibration temperature effects before correcting to the reference temperature.
5.3 When used in connection with bulk oil measurements, volume correction errors are minimized by observing the hydrometer
reading at a temperature close to that of the bulk oil temperature.
5.4 Density, relative density, or API gravity is a factor governing the quality and pricing of crude petroleum. However, this
property of petroleum is an uncertain indication of its quality unless correlated with other properties.
5.5 Density is an important quality indicator for automotive, aviation and marine fuels, where it affects storage, handling and
combustion.
6. Apparatus
6.1 Hydrometers, of glass, graduated in units of density, relative density, or API gravity as required, conforming to Specification
E100 or ISO 649-1, and the requirements given in Table 1.
6.1.1 The user should ascertain that the instruments used for this procedure conform to the requirements set out above with
respect to materials, dimensions, and scale errors. In cases where the instrument is provided with a calibration certificate issued
by a recognized standardizing body, the instrument is classed as certified and the appropriate corrections for the meniscus effect,
the thermal glass expansion effect, and alternative calibration temperature effects shall be applied to the observed readings prior
to corrections. Instruments that satisfy the requirements of this test method, but are not provided with a recognized calibration
certificate, are classed as uncertified.
6.2 Thermometers, having range, graduation intervals and maximum permitted scale error shown in Table 2 and conforming to
Specification E1 or IP Appendix A.
6.2.1 AlternateAlternative measuring devices or systems may be used, provided that the total uncertainty of the calibrated
system is no greater than that specified in 6.2. The stated repeatability and reproducibility values are not applicable if
alternatealternative fluids are used in the liquid-in-glass thermometers.
D1298 − 12b (2017)
TABLE 1 Recommended Hydrometers
A
Units Range Scale Meniscus
Each
A A
Total Interval Error Correction
Unit
Density, kg/m at 15°C 600 - 1100 20 0.2 ± 0.2 +0.3
600 - 1100 50 0.5 ± 0.3 +0.7
600 - 1100 50 1.0 ± 0.6 +1.4
Density, kg/m at 15 °C 600 - 1100 20 0.2 ± 0.2 +0.3
600 - 1100 50 0.5 ± 0.3 +0.7
600 - 1100 50 1.0 ± 0.6 +1.4
Relative density, 60/60°F 0.600 - 1.100 0.020 0.0002 ± 0.0002 +0.0003
0.600 - 1.100 0.050 0.0005 ± 0.0003 +0.0007
0.600 - 1.100 0.050 0.001 ± 0.0006 +0.0014
Relative density, 60/60 °F 0.600 - 1.100 0.020 0.0002 ± 0.0002 +0.0003
0.600 - 1.100 0.050 0.0005 ± 0.0003 +0.0007
0.600 - 1.100 0.050 0.001 ± 0.0006 +0.0014
Relative density, 60/60°F 0.650 - 1.100 0.050 0.0005 ±0.0005 +0.0007
Relative density, 60/60 °F 0.650 - 1.100 0.050 0.0005 ±0.0005 +0.0007
API Gravity −
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