ASTM E2551-07

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Designation: E2551 − 07
StandardTest Method for
Humidity Calibration (or Conformation) of Humidity
1
Generators for Use with Thermogravimetric Analyzers
This standard is issued under the fixed designation E2551; 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 3.2.2 water activity, n—the ratio of actual partial pressure of
water to the saturated water vapor pressure at the same
1.1 This test method describes the humidity calibration (or
temperature, expressed as a decimal fraction.
conformance) of humidity generators for use with thermogra-
3.2.2.1 Discussion—Water activity is also known as relative
vimetric analyzers and other thermal analysis apparatus. The
pressure in some applications areas.
humidity range covered is 5 to 95 % relative humidity (%RH)
3.2.3 first-deviation-from-baseline, n—the relative humidity
and the temperature range is 0 to 80 °C.
or water activity at which a deflection from the established
1.2 The values stated in SI units are to be regarded as
baseline is first observed.
standard. No other units of measurement are included in this
standard.
4. Summary of Test Method
1.3 There are no ISO equivalents to this standard.
4.1 Humidity generators are devices aimed at producing a
1.4 This standard does not purport to address all of the
specific level of humidity in the purge gas used by thermogra-
safety concerns, if any, associated with its use. It is the
vimetric analyzers or other thermal analysis apparatus. The
responsibility of the user of this standard to establish appro-
requested humidity levels may be held constant (isohum) or
priate safety and health practices and determine the applica-
increased or decreased in a continuous or stepped fashion.
bility of regulatory limitations prior to use.
4.2 The humidified purge gas is submitted to a thermogra-
vimetric analyzer in which the weight of a hygroscopic
2. Referenced Documents
material is observed. The relative humidity (or activity) of the
2
2.1 ASTM Standards:
moisture in the purge gas is stepped or scanned through a
D1193 Specification for Reagent Water
humidity range. At a fixed humidity of the purge gas, the test
E473 Terminology Relating to Thermal Analysis and Rhe-
specimen deliquesces and gains weight. In Method A, the
ology
humidity of the onset of this weight gain is taken as the
E1142 Terminology Relating to Thermophysical Properties
humidity calibration point. In Methods B and C, the rate of
E1582 Practice for Calibration of Temperature Scale for
weight change is zero at the humidity calibration point.
Thermogravimetry
5. Significance and Use
3. Terminology
5.1 This test method calibrates or demonstrates conformity
3.1 Specifictechnicaltermsusedinthisstandardaredefined
of the humidity level in a purge gas generated by a humidity
in Terminologies E473 and E1142. These terms include ther-
generator at a fixed temperature. Such calibration or demon-
mal curve and thermogravimetric analysis.
stration of conformity may be required by quality initiatives.
3.2 Definitions of Terms Specific to This Standard:
5.2 Conformance demonstrates that the humidified purge
3.2.1 relative humidity, n—the ratio of actual partial pres-
gas is within some established limits.
sure of water to the saturated water vapor pressure at the same
temperature, expressed as a percentage.
5.3 Calibration provides an offset and or slope value that
may be used for establishing the relative humidity scale of the
1
ThistestmethodisunderthejurisdictionofASTMCommitteeE37onThermal
apparatus.
Measurements and is the direct responsibility of Subcommittee E37.10 on
Fundamental, Statistical and Mechanical Properties.
6. Interferences
Current edition approved March 1, 2007. Published May 2007. DOI: 10.1520/
E2551-07.
6.1 Temperature regulation of any solution-head space en-
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
vironment to within 6 0.1 °C is essential for realizing
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
generated relative humidity values stable to within 6 1 %RH
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. (expected).
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E2551 − 07
7. Apparatus 7.3.2 A temperature sensor to provide an indication of the
specimen or furnace temperature to within 6 0.1 °C.
7.1 The humidity generator that is the focus of this standard
7.3.3 A continuously recording balance to measure the
may
...