ASTM E1782-98
(Test Method)Standard Test Method for Determining Vapor Pressure by Thermal Analysis
Standard Test Method for Determining Vapor Pressure by Thermal Analysis
SCOPE
1.1 This test method covers a procedure for the determination of the vapor pressure of pure liquids or melts from boiling point measurements made using differential thermal analysis (DTA) or differential scanning calorimetry (DSC) instrumentation operated at different applied pressures.
1.2 this test method may be used for the temperature range 273 to 773 K (0 to 500 degrees C) and for the pressures between 5 kPa to 2 MPa. These ranges may differ depending upon the instrumentation used and the thermal stability of materials tested. Because a range of applied pressures is required by this test method, the analyst is best served by use of instrumentation referred to as high pressure differential thermal instrumentation (HPDSC or HPDTA).
1.3 Computer or electronic-based instruments, techniques, or data treatment equivalent to this test method may also be used. Users of this test method are expressly advised that all such instruments or techniques may not be equivalent. It is the responsibility of the user of this test method to determine the necessary equivalency prior to use. In the case of dispute, only the manual procedures are to be considered valid.
1.4 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.
1.5 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
Designation:E 1782–98
Standard Test Method for
Determining Vapor Pressure by Thermal Analysis
This standard is issued under the fixed designation E 1782; 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.
1. Scope E380 Use of the International System of Units (SI)
E473 Terminology Relating to Thermal Analysis
1.1 This test method covers a procedure for the determina-
E691 Practice for Conducting an Interlaboratory Study to
tionofthevaporpressureofpureliquidsormeltsfromboiling
Determine the Precision of a Test Method
point measurements made using differential thermal analysis
E967 Practice for Temperature Calibration of Differential
(DTA) or differential scanning calorimetry (DSC) instrumen-
Scanning Calorimeters/Differential Thermal Analyzers
tation operated at different applied pressures.
E1142 Terminology Relating to Thermophysical Proper-
1.2 This test method may be used for the temperature range
ties
273 to 773 K (0 to 500°C) and for pressures between 5 kPa to
2 MPa. These ranges may differ depending upon the instru-
3. Terminology
mentation used and the thermal stability of materials tested.
3.1 Definitions:
Because a range of applied pressures is required by this test
3.1.1 The following terms are applicable to this test method
method, the analyst is best served by use of instrumentation
and can be found in either Terminology E473E473 or Termi-
referredtoashighpressuredifferentialthermalinstrumentation
nology E1142E1142: boiling pressure, boiling temperature,
(HPDSC or HPDTA).
differential scanning calorimetry (DSC), differential thermal
1.3 Computer or electronic-based instruments, techniques,
analysis (DTA), vapor pressure, vaporization point, vaporiza-
or data treatment equivalent to this test method may also be
tion temperature.
used. Users of this test method are expressly advised that all
3.2 Symbols:
such instruments or techniques may not be equivalent. It is the
3.2.1 A, B, C—Antoine vapor pressure equation constants
responsibility of the user of this test method to determine the
(log , kPa, K):
necessary equivalency prior to use. In the case of dispute, only
Antoine vapor pressure equation:Log P 5 A 2B/~T 1 C!
the manual procedures are to be considered valid.
1.4 The values stated in SI units are to be regarded as the
where:
standard. The inch-pound units given in parentheses are for
P = vapor pressure, kPa, and
information only.
T = temperature, K.
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
4.1 A specimen in an appropriate container is heated at a
priate safety and health practices and determine the applica-
constant rate within a DTAor DSC instrument operated under
bility of regulatory limitations prior to use.
anappliedconstantvacuum/pressurebetween5kPaand2MPa
until a boiling endotherm is recorded. Boiling is observed at
2. Referenced Documents
thetemperaturewherethespecimenpartialpressureequalsthe
2.1 ASTM Standards:
pressure applied to the test chamber. The pressure is recorded
E177 Practice for Use of the Terms Precision and Bias in
during observance of the boiling endotherm and the boiling
ASTM Test Methods
temperature is recorded as the extrapolated onset temperature.
Thismeasurementisrepeatedusingnewspecimensforeachof
five or more different pressures covering the pressure range of
This test method is under the jurisdiction of ASTM Committee E-37 on
interest. The pressure-temperature data are fitted as Log P
Thermal Measurements and is the direct responsibility of Subcommittee E37.01 on
−1
and 1/T(K ) to theAntoine vapor pressure equation (see Fig.
Test Methods and Recommended Practices.
CurrenteditionapprovedMarch10,1998.PublishedDecember1998.Originally
published as E1782–96. Last previous edition E1782–96.
2 3
Annual Book of ASTM Standards, Vol 14.02. Discontinued, see 1997 Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
E 1782–98
1). Vapor pressure values required for specific reports are then this method. This will be observed as an exotherm or a
computed from the derived equation. significantly broadened endotherm, or both, and shall not be
4.2 The capability of the assembled system after calibration consideredavalidpressure-temperaturedatumpoint.Useofan
should be periodically checked by using this method on pure inert gas for elevated pressures or for back-filling after evacu-
water as a reference substance and comparing the derived ation of the sample chamber is recommended to minimize the
vapor pressure data with the NBS/NRC steam tables attached risk of oxidation.
as Appendix X1. 6.3 Partial blockage of the pinhole in the DSC containers
could occasionally be encountered. This may be observed as
5. Significance and Use
noise spikes on the boiling endotherm and shall not be
5.1 Vapor pressure is a fundamental thermophysical prop- considered a valid pressure-temperature datum point.
erty of a liquid. Vapor pressure data are useful in process
7. Apparatus
design and control, in establishing environmental regulations
for safe handling and transport, for estimation of volatile
7.1 The essential equipment required to provide the mini-
organic content (VOC), and in deriving hazard assessments.
mum instrument capability of this test method includes (see
Vapor pressure and boiling temperature data are required for
Fig. 2):
Material Safety Data Sheets (MSDS). The enthalpy of vapor-
7.1.1 Differential Scanning Calorimeter (DSC) or Differen-
ization may also be estimated from the slope of the vapor
tial Thermal Analyzer (DTA), consisting of:
pressure curve.
7.1.1.1 DSC/DTA Test Chamber, composed of a furnace(s)
to provide uniform controlled heating of a specimen and
6. Interferences
referenceataconstantratewithinthe273to773Ktemperature
6.1 This test method is limited to materials that exhibit a
range of this test method; a temperature sensor to provide an
singularsharpboilingendothermundertheconditionsoutlined
indication of the specimen/furnace temperature to 61K;a
in this test method.
differential sensor to detect a difference (temperature or heat
6.2 Oxidation, pyrolysis, or polymerization of condensed
flow)betweenthespecimenandreferenceequivalentto5mW;
organic materials retained at temperatures above their ambient
and a means of sustaining an inert gas or vacuum test chamber
boiling point may be encountered at the elevated pressures of
NOTE—“A”, DSC/DTA instrument; “B,” pressure transducer;
“C,”pressure/vacuum source; “D,” pressure stabilizer; “E,” pressure
regulator; and “F,” relief valve.
FIG. 1 Vapor Pressure Curve with Experimental Data and
Antoine Equation Fig FIG. 2 Schematic of Apparatus
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
E 1782–98
environment at a purge rate of 10 mL/min or less 62% at 7.2 Auxiliary equipment considered useful in conducting
pressures above and below ambient. this test method include:
7.1.1.2 Temperature Controller, capable of executing a 7.2.1 Acoolantsystemthatcanbecoupleddirectlywiththe
specific temperature program by operating the furnace(s) controller to the furnace to hasten its recovery from elevated
between selected temperature limits to 61 K at a rate of temperatures or to sustain a subambient temperature to within
temperature change of 5 K/min constant within 61%. 61 K of a lower limit temperature.
7.1.1.3 Recording Device, either digital or analog, to record 7.2.2 Abalancetoweighspecimensorspecimencontainers,
and display the DSC/DTA curve with a Y-sensitivity of 5 or both, to 60.1 mg.
mW/cm or 0.5 K/cm and an X-sensitivity of 10 K/cm. 7.2.3 Asyringeormicropipettodeliverliquidspecimensof
7.1.2 Pressure/Vacuum System, consisting of: 1to5µL 610%.
7.1.2.1 Means of Sealing The Test Chamber, at any applied 7.2.4 Pressure relief valve to prevent accidental overpres-
absolute pressure within the 5 kPa to 2 MPa range of this test surizationinthepressuresystem.Aratingof10%inexcessof
method. theupperusepressureissuggestedprovideditdoesnotexceed
7.1.2.2 Source of Pressurized Gas, or vacuum capable of the maximum working pressure rating of any individual
sustaining a regulated inert gas pressure to the test chamber of component in the system.
between 5 kPa and 2 MPa.
8. Precautions
7.1.2.3 Pressure Transducer(s), to measure the pressure in
the test chamber to within 1% including any temperature 8.1 Safety Precautions:
8.1.1 Pressures in addition to ambient are employed in this
dependence of the transducer(s) over the range of 5 kPa to 2
MPa. test method. Ensure that the pressure/vacuum system is certi-
fied for operation at the extremes of pressure encountered with
NOTE 1—Distance (or dead volume) between the pressure transducer
this test method. Incorporation of a pressure relief device is
and the specimen in the test chamber should be minimized to ensure
recommended.
accurate recording of the pressure at the time of boiling.
8.1.2 Adequate provisions shall be available for retention
7.1.2.4 Pressure Regulator, or similar device to adjust the
and disposal of any spilled mercury if mercury-containing
applied pressure in the test chamber to 62% of the desired
pressure devices are employed.
value.
7.1.2.5 Ballast, or similar means to maintain the applied
9. Sampling
pressure in the test chamber constant to 61%.
9.1 Typical specimen sizes used for individual pressure
7.1.2.6 Valves,tocontroldeliveryoftheinertgas/vacuumto
measurements are 1 to 5 mg of solid or 1 to 5 µL of liquid.
the test chamber or to isolate components of the pressure/
Similar size specimens should be used for each individual
vacuum system, or both. Valves shall be rated in excess of the
measurement of a given sample.
2 MPa upper pressure limit of this test method.
9.2 Samples are assumed to be tested as received. Report
7.1.3 Containers, (pans, capillary tubes, etc.) that are inert
any special sampling or pretreatment used with this test
to the specimen and reference materials and which are of
method.
suitable structural shape and integrity to contain the specimen
and reference in accordance with the following specific re-
10. Calibration
quirements:
10.1 Perform calibration according to Practice E967E967,
7.1.3.1 It is imperative that the containers used in this test
usingtheheatingrateandspecimencontainersintendedforthis
method be capable of retaining the specimen in a manner
test method. Accomplish temperature calibration at ambient
which minimizes sample loss through vaporization prior to
pressure.
boiling and which promotes the development of vapor-liquid
NOTE 3—The effect of pressure on the melting temperature of pure
equilibrium at boiling. When both conditions are met a sharp
materials used to calibrate the temperature axis has been shown to be
endotherm with little or no baseline curvature at the onset will
<0.01 K at the maximum pressure of this method (3). The effects of
be observed.
vacuum on the heat transfer characteristics and subsequent thermal lag of
various differential thermal instruments (DSC and DTA) have not been
NOTE 2—Studies by ASTM task group E37.01.05 and others (1,2)
established. From general experiences these effects should not alter the
havedeterminedglasscylindricalcontainersof2to4mminsidediameter
temperatureaxiscalibrationbymorethan1Kattheminimumpressureof
by 25 mm long are suitable for thermocouple inserted style DTA
this test method.
instruments; and a hermetic sealable pan (approximately 40 µL vol) with
a single pinhole in the center of the lid of#125 µm diameter is suitable
10.2 Calibrate the pressure transducer according to the
for DSC instruments. For purposes of this test method, pinhole diameters
recommendations of the manufacturer or similar appropriate
of 50 to 75 µm are recommended. These pinhole dimensions for DSC
procedure.
containers were established specifically for use with heating rates of
nominally 5 K/min. Use of heating rates other than 5 K/min are not
11. Procedure
recommended for this test method. Higher rates may result in some
self-pressurization of the specimen and lesser rates will extend measure-
11.1 Place the specimen and inert reference in suitable
ment times and will tend to promote preboiling vaporization.
containers (see 7.1.3) into the test chamber.
NOTE 4—If hermetic sealable DSC pans with pinholed lids are used,
make sure there is no sample material on the outer surfaces of the
The boldface numbers given in parentheses refer to a list of references at the
end of the text. containerandthatagoodhermeticsealisaccomplished.Eitherwillresult
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
E 1782–98
inpreboilingvaporizationthatatleastpartiallynegatesthefunctionofthe NOTE 8—Deviations from linearity (curvature) due to expected de-
pinhole. Be certain, also, that the pinhole is free of dirt or debris. creases in enthalpy of vaporization with temperature (Antoine equation
“C” constant negative) should not be confused with the abrupt deviation
11.2 Seal the test chamber and apply the desired pressure.
due to decomposition or polymerization. Curvature of normal data is
barely perceptible.
NOTE 5—It is recommended to flush residual oxygen from the test
chamber by either purging for several minutes with inert gas or by
12.3 Calculate the Antoine vapor pressure equation con-
evacuation and back-filling with inert gas.
stants: A, B, and C retaining all available decimals using a
11.3 Allow the pressure to stabilize and equilibrate the test
nonlinear least-squares regression program to fit the Antoine
chamber at a start temperature which shall be at least 30 K
equation, Log P=A− B/(T + C) to the corrected pressure-
below the expected boiling temperature to ensure stable
temperature data points. Data for which any of the fitted
temperature control and baseline.
AntoineequationconstantsfalloutsideofrangesgiveninNote
11.4 Heat the specimen and reference at a cons
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.