ASTM E2071-21

Standard Practice for Calculating Heat of Vaporization or Sublimation from Vapor Pressure Data

ABSTRACT
This practice describes the calculation of the heat of vaporization of a liquid or the heat of sublimation of a solid from measured vapor pressure data. It is applicable to pure liquids, azeotropes, pure solids, and homogenous solid solutions over the temperature range for which the vapor pressure equation fitted to the measured data is applicable. Vapor pressure data shall be measured in accordance to the test methods and shall be correlated with the Antoine equation. The heat of vaporization or sublimation is computed at the desired temperature from the vapor-pressure temperature derivative from the fitted Antoine equation by use of the Clapeyron equation.
SCOPE
1.1 This practice describes the calculation of the heat of vaporization of a liquid or the heat of sublimation of a solid from measured vapor pressure data. It is applicable to pure liquids, azeotropes, pure solids, and homogenous solid solutions over the temperature range for which the vapor pressure equation fitted to the measured data is applicable.  
Note 1: This practice is generally not applicable to liquid mixtures. For a pure liquid or azeotrope, composition does not change upon vaporization so that the integral heat of vaporization is identical to the differential heat of vaporization. Non-azeotropic liquid mixtures change composition upon vaporizing. Heat of vaporization data computed from this practice for a liquid mixture are valid only as an approximation to the mixture differential heat of vaporization; it is not a valid approximation to the mixture integral heat of vaporization.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 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.

General Information

• Status: Published
• Publication Date: 28-Feb-2021
• ICS: 27.040 - Gas and steam turbines. Steam engines
• Technical Committee: E37 - Thermal Measurements
• Drafting Committee: E37.10 - Fundamental, Statistical and Mechanical Properties

Standards Content (Sample)

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.
Designation: E2071 − 21
Standard Practice for
Calculating Heat of Vaporization or Sublimation from Vapor
1
Pressure Data
This standard is issued under the fixed designation E2071; 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.
1. Scope tionship and Initial Decomposition Temperature of Liq-
uids by Isoteniscope
1.1 This practice describes the calculation of the heat of
E1142 Terminology Relating to Thermophysical Properties
vaporization of a liquid or the heat of sublimation of a solid
E1194 Test Method for Vapor Pressure
from measured vapor pressure data. It is applicable to pure
E1719 Test Method for Vapor Pressure of Liquids by Ebul-
liquids, azeotropes, pure solids, and homogenous solid solu-
liometry
tions over the temperature range for which the vapor pressure
E1782 Test Method for Determining Vapor Pressure by
equation fitted to the measured data is applicable.
Thermal Analysis
NOTE 1—This practice is generally not applicable to liquid mixtures.
For a pure liquid or azeotrope, composition does not change upon
3. Terminology
vaporization so that the integral heat of vaporization is identical to the
differential heat of vaporization. Non-azeotropic liquid mixtures change
3.1 Symbols:
composition upon vaporizing. Heat of vaporization data computed from
3.1.1 A, B, C—Antoine vapor pressure equation constants
this practice for a liquid mixture are valid only as an approximation to the
(log , kPa, K), Antoine vapor pressure equation:
mixture differential heat of vaporization; it is not a valid approximation to 10
the mixture integral heat of vaporization.
log P 5 A 2 B/~T1C! (1)
10
1.2 The values stated in SI units are to be regarded as
3.1.2 P—vapor pressure, kPa.
standard. No other units of measurement are included in this
3.1.3 P —critical pressure, kPa.
c
standard.
3.1.4 P —reduced pressure = P/P .
1.3 This standard does not purport to address all of the r c
safety concerns, if any, associated with its use. It is the
3.1.5 T—absolute temperature, K.
responsibility of the user of this standard to establish appro-
3.1.6 T —critical temperature, K.
c
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use. 3.1.7 T —reduced temperature = T/T .
r c
1.4 This international standard was developed in accor- 3
3.1.8 V—molar volume, cm /mol.
dance with internationally recognized principles on standard-
3
3.1.9 R—gas constant, 8.31433 J/mol-K; 8314330 kPa-cm /
ization established in the Decision on Principles for the
mol-K.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.1.10 ∆H —heat of vaporization, J/mol.
V
Barriers to Trade (TBT) Committee.
3.1.11 ∆Z —difference in compressibility factor (Z = PV/
V
RT) upon vaporization. Clapeyron equation:
2. Referenced Documents
2
∆H 52R∆Z @d~lnP!/d~1/T!# (2)
V V
2.1 ASTM Standards:
3.1.11.1 Discussion—The subscript “V” will be used
D2879 Test Method for Vapor Pressure-Temperature Rela-
throughout this practice to designate the vaporization of a
liquid. If the vapor pressure data were measured for a solid,
1
This practice is under the jurisdiction of Committee E37 on Thermal Measure-
substitute the subscript “S” for the sublimation of a solid.
ments and is the direct responsibility of Subcommittee E37.10 on Fundamental,
Statistical and Mechanical Properties. 3.2 Definitions—Specialized terms used in this practice are
Current edition approved March 1, 2021. Published April 2021. Originally
defined in Terminology E1142.
approved in 2000. Last previous edition approved in 2015 as E2071 – 00 (2015).
3.2.1 sublimation—transition from a solid phase to a gas-
DOI: 510.1520/E2071-21.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or eous phase.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3.2.2 vaporization—transition from a liquid phase to a
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. gaseous phase.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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E2071 − 21
2 2
4. Summary of Practice d lnP /d 1/T 522.3025851 BT / T1C (3)
@ ~ ! ~ !# @ ~ ! #
7.2 Calculate an approximation to∆Z at each temperature.
4.1 Vapor pressure data are measured by other referenced
V
...

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: E2071 − 00 (Reapproved 2015) E2071 − 21
Standard Practice for
Calculating Heat of Vaporization or Sublimation from Vapor
1
Pressure Data
This standard is issued under the fixed designation E2071; 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.
1. Scope
1.1 This practice describes the calculation of the heat of vaporization of a liquid or the heat of sublimation of a solid from
measured vapor pressure data. It is applicable to pure liquids, azeotropes, pure solids, and homogenous solid solutions over the
temperature range for which the vapor pressure equation fitted to the measured data is applicable.
NOTE 1—This practice is generally not applicable to liquid mixtures. For a pure liquid or azeotrope, composition does not change upon vaporization so
that the integral heat of vaporization is identical to the differential heat of vaporization. Non-azeotropic liquid mixtures change composition upon
vaporizing. Heat of vaporization data computed from this practice for a liquid mixture are valid only as an approximation to the mixture differential heat
of vaporization; it is not a valid approximation to the mixture integral heat of vaporization.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 There is no ISO standard equivalent to this practice.
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 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
2.1 ASTM Standards:
D2879 Test Method for Vapor Pressure-Temperature Relationship and Initial Decomposition Temperature of Liquids by
Isoteniscope
E1142 Terminology Relating to Thermophysical Properties
E1194 Test Method for Vapor Pressure
E1719 Test Method for Vapor Pressure of Liquids by Ebulliometry
E1782 Test Method for Determining Vapor Pressure by Thermal Analysis
1
This practice is under the jurisdiction of Committee E37 on Thermal Measurements and is the direct responsibility of Subcommittee E37.10 on Fundamental, Statistical
and Mechanical Properties.
Current edition approved May 1, 2015March 1, 2021. Published May 2015April 2021. Originally approved in 2000. Last previous edition approved in 20102015 as
E2071 – 00 (2010).(2015). DOI: 510.1520/E2071-00R15.510.1520/E2071-21.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E2071 − 21
3. Terminology
3.1 Symbols:
3.1.1 A, B, C—Antoine vapor pressure equation constants (log , kPa, K), Antoine vapor pressure equation:
10
log P 5 A 2 B/ T1C (1)
~ !
10
3.1.2 P—vapor pressure, kPa.
3.1.3 P —critical pressure, kPa.
c
3.1.4 P —reduced pressure = P/P .
r c
3.1.5 T—absolute temperature, K.
3.1.6 T —critical temperature, K.
c
3.1.7 T —reduced temperature = T/T .
r c
3
3.1.8 V—molar volume, cm /mol.
3
3.1.9 R—gas constant, 8.31433 J/mol-K; 8314330 kPa-cm /mol-K.
3.1.10 ΔH —heat of vaporization, J/mol.
V
3.1.11 ΔZ —difference in compressibility factor (Z = PV/RT) upon vaporization. Clapeyron equation:
V
ΔH 52RΔZ d lnP /d 1/T (2)
@ ~ ! ~ !#
V V
ΔH 52RΔZ d lnP /d 1/T (2)
@ ~ ! ~ !#
V V
3.1.11.1 Discussion—
The subscript “V” will be used throughout this practice to designate the vaporization of a liquid. If the vapor pressure data were
measured for a solid, substitute the subscript “S” for the sublimation of a solid.
3.2 Definitions:Definitions
3.2.1 Specialized terms used in this practice are defined in Terminology E1142.—Specialized terms u
...