ASTM D2284-95(2002)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D2284 – 95 (Reapproved 2002)
Standard Test Method for
Acidity of Sulfur Hexafluoride
This standard is issued under the fixed designation D2284; 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.
hexafluoride at 25°C and 1 atm. of pressure (normal temperature and
1. Scope
pressure) is 5.97 g/L.Alternatively, the sample weight may be determined
1.1 This test method covers the determination of the acidic
by weighing the sample cylinder before and after sampling.
fluorides of sulfur hexafluoride (SF ).
1.2 This standard does not purport to address all of the
6. Reagents
safety concerns, if any, associated with its use. It is the
6.1 Purity of Reagents—Use reagent grade chemicals in all
responsibility of the user of this standard to establish appro-
tests. Unless otherwise indicated, it is intended that all reagents
priate safety and health practices and determine the applica-
shall conform to the specifications of the Committee on
bility of regulatory limitations prior to use.
Analytical Reagents of theAmerican Chemical Society, where
such specifications are available. Other grades may be used,
2. Referenced Documents
provided it is first ascertained that the reagent is of sufficiently
2.1 ASTM Standards:
high purity to permit its use without lessening the accuracy of
D1193 Specification for Reagent Water
the determination.
D2472 Specification for Sulfur Hexafluoride
6.2 Purity of Water—Unless otherwise indicated, references
to water shall be understood to mean reagent grade water
3. Summary of Test Method
conforming to Specification D1193.
3.1 Acidic constituents of the sample are absorbed in
6.3 Phenolphthalein Indicator Solution (10 g/L)—Dissolve
slightly alkaline water containing an indicator and the excess
1 g of phenolphthalein in 100 mL of ethanol (95 %).
base titrated with a standard acid solution.The resultant acidity
6.4 Sodium Hydroxide Solution (0.01 N)—Dissolve 0.4 6
is expressed as equivalents of hydrofluoric acid (HF).
0.01 g of sodium hydroxide (NaOH) in water and dilute to 1 L.
Prepare a fresh solution weekly. Standardize by titrating
4. Significance and Use
against a weighed amount of potassium acid phthalate.
4.1 Acidic fluorides are undesirable in SF used as an
6.5 Sulfuric Acid (0.01 N)—Add 0.25 mL of concentrated
electrical insulating gas in that they may contribute to corro-
sulfuric acid (H SO , sp gr 1.84) to water and dilute to 1 L.
2 4
sion or constitute dielectric hazard.
Standardize against standard 0.01 N NaOH solution.
4.2 This test method is valid for both new and used SF.In
used SF , it will only measure those active species which are
7. Sampling
hydrolyzable.
7.1 Take the sample as a liquid from the cylinder to be
sampled.Thismaybedonebyinvertingthecylindersothatthe
5. Apparatus
outlet valve is at the bottom.
5.1 Gas Washing Bottles, 500-mL capacity, two required.
5.2 Microburet, graduated to 0.01 mL.
8. Preparation of Apparatus
5.3 Wet Test Meter.
8.1 Place the cylinder to be sampled as suggested in Section
NOTE 1—The meter is used to measure the volume of dry gas in litres 7andconnectaneedlevalvetothecylinderoutlet.Connectthe
and hence the weight of SF samples. The density of sulfur hexafluoride
inlet of one of the gas sampling bottles to the cylinder needle
at 0°C and 1 atm. of pressure (STP) is 6.52 g/L. The density of sulfur
valve and the outlet to the wet test meter. Flexible rubber or
plastic tubing can be used. Set the meter to zero and note the
reading.
This test method is under the jurisdiction of ASTM Committee D27 on
Electrical Insulating Liquids and Gases and is the direct responsibility of Subcom-
mittee D27.06 on Chemical Test. Reagent Chemicals, American Chemical Society Specifications, American
Current edition approved March 15, 1995. Published May 1995. Originally Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
publishedasD2284 – 64T.LastpreviouseditionD2284 – 88.DOI:10.152
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