ASTM E2071-21

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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
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volume information, refer to the standard’s Document Summary page on the ASTM website.
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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
...