ASTM E2551-07
(Test Method)Standard Test Method for Humidity Calibration (or Conformation) of Humidity Generators for Use with Thermogravimetric Analyzers
Standard Test Method for Humidity Calibration (or Conformation) of Humidity Generators for Use with Thermogravimetric Analyzers
SIGNIFICANCE AND USE
This test method calibrates or demonstrates conformity of the humidity level in a purge gas generated by a humidity generator at a fixed temperature. Such calibration or demonstration of conformity may be required by quality initiatives.
Conformance demonstrates that the humidified purge gas is within some established limits.
Calibration provides an offset and or slope value that may be used for establishing the relative humidity scale of the apparatus.
SCOPE
1.1 This test method describes the humidity calibration (or conformance) of humidity generators for use with thermogravimetric analyzers and other thermal analysis apparatus. The humidity range covered is 5 to 95 % relative humidity (%RH) and the temperature range is 0 to 80 °C.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 There are no ISO equivalents to this standard.
1.4 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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E2551 − 07
StandardTest Method for
Humidity Calibration (or Conformation) of Humidity
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
2.1 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
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-
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).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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 be an accessory providing a humidified purge gas to some
specimen weight with a minimum capacity of 100 mg and
otherthermalanalysisapparatus(typicallyathermogravimetric
sensitivity of 6 10 µg.
analyzer) or it may be part of a self-contained instrument that
7.3.4 Ameans of maintaining the specimen/container under
includes both the humidity generator and the thermal analysis
apparatus. In the former case, some of the components de- atmospheric control at a purge rate of 10 to 200 mL/min 6 10
mL/min or 1 %, whichever is greater.
scribed below may be redundant.
7.3.5 A temperature controller capable of executing a spe-
7.2 Humidity Generator—The essential instrumentation re-
cific temperature program by operating the furnace between
quired to provide the minimum humidity generator capability
selected temperature limits at a rate of temperature change of
for this method includes:
0.5 °C/min constant to within 6 0.1 °C/min or to an isothermal
7.2.1 Temperature Sensor—to provide an indication of the
temperature that is maintained constant to within 6 0.1 °C for
purge gas temperature readable to within 6 0.1 °C.
a minimum of 100 h.
7.2.2 Temperature Controller—capable of executing a spe-
7.3.6 Containers (pans, crucibles, etc.) that are inert to the
cific temperature program by operating heaters or coolers
between selected temperature limits at a rate of temperature specimen and that will remain gravimetrically stable within the
temperature limits of this method.
change of 0.5 °C/min constant to 6 0.1 °C/min or at an
isothermal temperature constant to within 6 0.1 °C.
7.3.7 Data storage capable of storage of the weight and
7.2.3 Humidity Sensor—capable of indicating the humidity
relative humidity signals.
of the purge gas over the range of 5 to 95 % relative humidity
7.3.8 A display capable of plotting a thermal curve with
(%RH) readable to within 6 0.1 %RH.
weight on the ordinate (Y-axis) and relative humidity (or
7.2.4 Humidity Controller—capable of executing a specific
activity) on the abscissa (X-axis) with a sensitivity of 10 µg for
humidity program by operating purge gas humidifiers between
weight and 0.1 %RH, respectively.
selected humidity limits at a rate of humidity change of
0.5 %RH/min constant to within 6 0.1 %RH or at an isohum
8. Reagents and Materials
relative humidity to within 6 0.1 %RH.
8.1 One or more inorganic salts taken from Table 1 selected
7.2.5 Purge Gas Flow Sensor—capable of measuring purge
to provide the humidity range of interest.
gas flow readable to within 6 0.1 mL/min.
7.2.6 Purge Gas Flow Controller—capable of controlling
8.2 Purity of Reagents—Reagentgradechemicals(orbetter)
purge gas flow readable to within 6 0.1 mL/min.
shall be used for preparation of all standard solutions.
7.2.7 Humdifier element—capableofgeneratingpurgegases
8.3 Purity of Water—Reagent water produced by distillation
with relative humidity continuously over the range of 5 to
or by ion exchange, or reverse osmosis followed by distillation
95 %RH.
shall be used (see Specification D1193).
7.3 Thermogravimetric Analyzer (TGA)—The essential in-
strumentation required to provide the minimum thermogravi-
9. Hazards
metric analytical capability for this method includes:
7.3.1 A furnace to provide uniform controlled heating or 9.1 Salt solutions are extremely corrosive to apparatus if
coolingofaspecimentoaconstanttemperatureorataconstant spilled. Care shall be taken in their preparation and handling to
rate within the applicable temperature range of this method. prevent contact with appara
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.