ASTM D3429-93(2002)e1

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Designation: D 3429 – 93 (Reapproved 2002)
Standard Test Method for
Solubility of Fixed Gases in Low-Boiling Liquids
This standard is issued under the fixed designation D3429; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Warnings were moved from notes to section text editorially December 2002.
1. Scope 3.1.2 test gas, n—gas whose solubility is being determined.
3.1.3 liquid or test liquid—solvent for test gas.
1.1 This test method covers the determination of the solu-
3.1.4 vapor, n—vapor phase of test liquid.
bilities of nonreactive gases such as nitrogen and helium in
3.1.5 nonreactive gas, n—gasthatdoesnotreactchemically
liquids that boil below 273 K.This test method is applicable at
with the test liquid.
temperatures from 77 to 300 K from subambient pressure to
3.1.6 elution, n—the process of removing a material ab-
6.5 MPa (65 atm). This test method does not provide for
sorbed on the stationary phase of the gas chromatograph
analysis of the vapor phase in equilibrium with the liquid (see
column by displacing it with the flowing carrier gas.
Section 3 for a description of terms).
3.1.7 fractionation, n—change of composition caused by
1.2 This test method as written describes the procedures to
change of pressure.
be followed for determination of the solubilities of helium and
nitrogen. If suitable modifications are made to the analytical
4. Summary of Test Method
measurements by gas chromatography, solubilities of other
4.1 Asample of test liquid A is saturated with test gas B at
gases such as argon, hydrogen, oxygen, etc., can be deter-
specified temperature and pressure.Aportion of the solution is
mined.
withdrawn and vaporized in an evacuated sample container at
1.3 The values stated in SI units are to be regarded as the
room temperature.The concentration of gas B in the vaporized
standard. In cases where materials, products, or equipment are
sample is determined by gas chromatography. It is necessary
available in inch-pound units only, SI units are omitted.
that the molar concentration of the gas in the sample container
1.4 This standard does not purport to address all of the
be the same as in the liquid phase. This will be true if
safety concerns, if any, associated with its use. It is the
fractionation of the sample is avoided while withdrawing it
responsibility of the user of this standard to establish appro-
from the liquid phase, if no decomposition or polymerization
priate safety and health practices and determine the applica-
ofthetestliquidoccursonvaporization,andifthevaporofthe
bility of regulatory limitations prior to use. For specific hazard
testliquiddoesnotreactwiththewallsofthesamplecontainer
statements, see 6.1.2 and 7.1 and Annex A1.
or connecting lines. It is also necessary that both the test gas
2. Referenced Documents andthevaporofthetestliquidbehavenearlyideallyat101kPa
(1atm).Iftheaboverequirementsaremet,thistestmethodwill
2.1 ASTM Standards:
give estimates of solubility with an accuracy of 62%.
E260 Practice for Packed Column Gas Chromatography
5. Significance and Use
3. Terminology
5.1 The solubility of fixed gases in liquids is an important
3.1 Definitions of Terms Specific to This Standard:
engineering parameter in the design of hydraulic systems. It is
3.1.1 carriergas,n—gasusedtosweepsamplesthroughthe
a measure of the amount of gas that can be released from
gas chromatograph.
solution when a system undergoes changes in pressure and
temperature. Theoretical considerations permit approximate
This test method is under the jurisdiction of ASTM Committee D02 on values of gas solubility to be computed with reasonable
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
accuracy. Dissolved gases are separated and quantified chro-
D02.11 on Engineering Sciences of High Performance Fluids and Solids.
matographically. The test method is restricted to use with
Current edition approved Aug. 15, 1993. Published October 1993. Originally
low-boiling liquid samples.
published as D3429–75. Last previous edition D3429–87.
Annual Book of ASTM Standards, Vol 03.06.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D 3429 – 93 (2002)
6. Apparatus 6.1.2 Nitrogen Vapor Cryostat, with suitable temperature
measurement and control devices, to provide the low-
6.1 Saturator and Sampler System, suitable for the tests of
temperature environment for the high-pressure test chamber.
low-boilingliquidsandgasesatvariouspressuresandtempera-
The cryostat consists of a cylindrical stainless steel Dewar or
tures, shown schematically in Fig. 1. The system comprises
other suitable insulated container not less than 0.3 m in inside
four parts:
diameter and approximately 0.5 m in inside depth.Asolenoid
6.1.1 High-Pressure Test Chamber,withinternalcapacityof
valveisusedtoadmitliquidnitrogentothecryostat.Theliquid
approximately(1L)suchasshowninFig.2.Thelidofthetest
nitrogencoolsthecryostatanditscontents.Theliquidnitrogen
chamber is equipped with three ports. The first is to contain a
(Warning—See 7.1.) should be introduced through a diffuser,
thermocouple well, the second is for the addition of the test
or in a fine stream behind a sheet metal baffle, so that liquid
liquid and pressurization of the system with the test gas, and
does not impinge directly on the test chamber or the controller
the third port is for withdrawal of the sample of solution from
thermocouple.Thelattermaybeattachedlooselytothesideof
the liquid phase by means of an eductor tube which extends to
thetestchamberforconvenience,butgoodthermalcouplingto
the bottom of the chamber. The high-pressure assembly is
the chamber must not be made. Although the nitrogen vapor
mountedsothatanoscillatingmotioninahorizontalplanecan
cryostat can undergo temperature excursions of several de-
be applied to it mechanically with a frequency of 1 Hz (one
cycle per second) and an amplitude of 0.02 m. Loops (pigtails) grees, the test chamber will stabilize at a temperature that
varies by only a few tenths of a degree because of its thermal
are formed in the connecting metal lines to the test chamber to
avoid undue stress. inertia.Tominimizeheattransferfromoutsideoftheapparatus
and frost condensation, the top of the cryostat should be
6.1.1.1 An electric motor geared down to provide a shaft
speed of about 60 rpm is convenient for providing the loosely covered with a lid of foamed glass or plastic, or other
necessary agitation. An eccentric or connecting rod from the similar insulating material. (Warning—Extremely cold. Lib-
motor shaft to the support rod imparts an oscillating motion. erates gas that can cause suffocation. Contact with skin causes
Without agitation an excessive time is required for equilibrium burns or freezing, or both. Vapors can react violently with hot
to be established. magnesium or aluminum alloys. See A1.1.)
NOTE 1—All lines and fittings 300 series stainless steel.
1. VI through V8—Stainless steel valves, metal-to-metal seat, bellows in the middle half of the scale, balance 6 3 % or better), com-
sealed 14 MPa (2000 psi) rating (V8 modified, see Fig. 3) pound range from 0 to 30 in. Hg and a gage pressure from 0 to
2. T/C-1—Copper-constantan thermocouple, test liquid temperature. 103 kPa (0 to 15 psi).
3. T/C-2—Copper-constantan thermocouple, vapor cryostat temperature con- 6. Burst Disk—Select to release at 50 % higher than maximum desired system
troller. pressure
4. G-1—Bourdon gage, 4 ⁄2 or 6-in. size, Grade 3A (accuracy 60.25 % of 7. Temperature Controller—Range 77 to 300 K, accuracy 60.5 % full range
maximum reading), range 1.5 times highest desired system pressure. 8. L—Loops in stainless steel lines for flexibility.
5. G-2—Bourdon gage, 3 ⁄2 to 6-in. size, Grade A or B (accuracy 2 % or better 9. R1 and R2—Gas pressure regulators with pressure gage.
FIG. 1 Saturator Apparatus—Schematic
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D 3429 – 93 (2002)
NOTE 1—All material 300 series stainless except flange gasket. Design of perforated baffles not critical but leave 6-mm diameter holes spaced on
20-mm centers are recommended. Baffles should be spot-welded to the inside of the chamber to prevent movement. The purpose of the baffles is to
increase turbulence in the liquid and thereby increase the rate of solubility of gas in the test liquid.
NOTE 2—The conflat flange manufactured by the Varian Corp. of Palo Alto, CA, is suitable.
FIG. 2 Test Chamber Detail
6.1.3 Vacuum and Pressurization Manifold, required for amount of liquid lost through purging, the sample valve (V8 in
initial evacuation of the test chamber, filling the chamber with Fig. 1) should be modified to reduce liquid holdup to a
the test liquid, and pressurizing the chamber with the test gas minimum.The details of this modification are shown in Fig. 3.
to the desired total pressure.The manifold is shown on the left 6.2 Gas Chromatograph, required for determination of the
side of Fig. 1.
gasconcentrationinthesample.Itmustbeequippedwithagas
6.1.3.1 The burst disk shown in Fig. 1 shall be of the type sampling valve. It is desirable that two different size loops be
capable of withstanding an external pressure of 101 kPa (1 provided so that the sample size can be adjusted depending on
atm) when the system is evacuated.
theconcentrationoftestgastobedetermined.Sampleloopsof
6.1.3.2 The pump used to evacuate the apparatus shall be a 0.5 and 2.0 mL are recommended. The gas chromatograph
good quality oil-filled mechanical pump capable of producing
system must permit easy and rapid change of carrier gas and
−6
an ultimate vacuum of 0.1 Pa (10 atm) or better. If conden- columns to suit a wide variety of analytical requirements. A
sible vapors or reactive vapors are to be pumped, the pump
thermal conductivity detector of the glass-coated bead type is
shallbeprotectedbyasuitableabsorberorcoldtrap.Thepump recommended. The instrumentation should provide a variable
shall run continuously for the duration of the test.
attenuator for the detector signal so that a wide range of fixed
6.1.4 Solution-Sampling System—This system utilizes a gas concentrations may be accommodated. A suitable chart
3-mm ( ⁄8-in.) outside diameter heavy-wall stainless steel
recorder, preferably equipped with integrator, should be pro-
eductor tube extending nearly to the bottom of the test vided. Alternatively, a digital readout may be used. A typical
chamber. The eductor tube end extending outside the chamber
gas chromatograph is shown schematically in Fig. 4, and its
is connected to a valve just above the top of the cryostat, and power supply is shown in Fig. 5.
the outlet of this valve leads to a sample cylinder or container
NOTE 1—Practice E260 provides further description.
of about 100-mL volume. Each time a sample is withdrawn
from the liquid phase, the eductor tube and sampling valve 6.3 Leak Testing—All parts of the system should be tested
must be purged, otherwise the liquid and vapor in the line will with helium for leakage at a pressure 1.5 times test operating
not necessarily be of equilibrium composition. To reduce the pressure and vacuum leak tested. The test should include
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D 3429 – 93 (2002)
NOTE 1—Stainless steel wire extends from the position shown in the valve to the lower end of the eductor tube. The purpose of this modification is
to reduce the volume of the valve upstream of the poppet to minimum. A valve with a blunt poppet, rather than a needle, is preferred for this service.
FIG. 3 Sampling Valve (V8) Modification
FIG. 4 Gas Chromatograph Schematic
externalleaksandport-to-portleaksinvalves.Thetotalsystem absolutemolefractionoftheheliumconcentration.Nitrogenis
maximum acceptable leak rate is 0.1 std cm atm/s. A mass used as the carrier gas when helium is the gas whose solubility
spectrometer leak detector is suitable for the leak rate mea- is to be determined. Helium is used as the carrier gas when
surements. nitrogen solubility is being determined. (Warning—
Compressed gas under high pressure. Gas reduces oxygen
7. Reagents and Materials
available for breathing. See A1.2.)
7.1 Calibration Mixtures—Gas Chromatography—For the 7.2 Column Materials—Because only two-component sys-
determination of nitrogen solubility, one or more mixtures of tems are analyzed and the boiling points of the test gas and
nitrogen in helium are required for calibration of the gas liquid are relatively far apart, a relatively short column is
chromatograph. Concentrations of 2% and 10% are recom- sufficient to provide resolution. For most test liquids, a 0.2-m
mended. The exact concentration of each mixture must be column of silica gel or molecular sieve will separate the test
accuratelyknownto 61%oftheabsoluteconcentrationofthe gasandtestliquid.Thecolumnshouldbeconstructedof6-mm
minor constituent. Certified calibration mixtures are available (0.25-in.) thin-walled stainless steel tubing. Certain reactive
from suppliers of commercial cylinder gases. For the determi- test liquids, particularly the powerful oxidizers that contain
nation of helium solubilities, mixtures of helium in nitrogen fluorine, may react with the stationary phase materials to
containing about 0.2% and 1.0% helium are recommended. produce interferences. If this is the case, more elaborate
The exact concentration should be known to 61% of the columns must be used to afford resolution. Each combination
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D 3429 – 93 (2002)
FIG. 5 Power Supply Schematic
of gas and liquid poses its own particular analytical problem prevent injury to operating personnel in the event of rupture of
and a certain amount of experimentation with stationary phase the equipment, and the portion of the eductor tube which is
materials may be required. Table 1 contains a list of materials
outside of the test chamber must be used in an explosion-proof
found appropriate for some typical test gas/liquid combina- hood.
tions.
7.3 Gases, Compressed—High-purity helium and nitrogen,
9. Procedure
or other test gases, are required for saturating the test liquids.
9.1 Evacuate the test chamber and the transfer manifold by
The same gases are required for carrier gases in the gas
opening the vacuum valve V3 (Fig. 1).
chromatograph. (Warning—see 7.1.)
9.2 Set the temperature controller and cool the cryostat to a
8. Safety Precautions
temperature near the temperature at which the solubility
measurement is to
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