1、Designation: D 3429 93 (Reapproved 2007)An American National StandardStandard Test Method forSolubility of Fixed Gases in Low-Boiling Liquids1This standard is issued under the fixed designation D 3429; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the solu-bilities of nonreactive gases su
3、ch as nitrogen and helium inliquids that boil below 273 K. This test method is applicable attemperatures from 77 to 300 K from subambient pressure to6.5 MPa (65 atm). This test method does not provide foranalysis of the vapor phase in equilibrium with the liquid (seeSection 3 for a description of te
4、rms).1.2 This test method as written describes the procedures tobe followed for determination of the solubilities of helium andnitrogen. If suitable modifications are made to the analyticalmeasurements by gas chromatography, solubilities of othergases such as argon, hydrogen, oxygen, etc., can be de
5、ter-mined.1.3 The values stated in SI units are to be regarded as thestandard. In cases where materials, products, or equipment areavailable in inch-pound units only, SI units are omitted.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is
6、theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see 6.1.2 and 7.1 and Annex A1.2. Referenced Documents2.1 ASTM Standards:2E 260 Practice for Pa
7、cked Column Gas Chromatography3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 carrier gas, ngas used to sweep samples through thegas chromatograph.3.1.2 test gas, ngas whose solubility is being determined.3.1.3 liquid or test liquidsolvent for test gas.3.1.4 vapor, nvapor phas
8、e of test liquid.3.1.5 nonreactive gas, ngas that does not react chemicallywith the test liquid.3.1.6 elution, nthe process of removing a material ab-sorbed on the stationary phase of the gas chromatographcolumn by displacing it with the flowing carrier gas.3.1.7 fractionation, nchange of compositio
9、n caused bychange of pressure.4. Summary of Test Method4.1 A sample of test liquid A is saturated with test gas B atspecified temperature and pressure. A portion of the solution iswithdrawn and vaporized in an evacuated sample container atroom temperature. The concentration of gas B in the vaporized
10、sample is determined by gas chromatography. It is necessarythat the molar concentration of the gas in the sample containerbe the same as in the liquid phase. This will be true iffractionation of the sample is avoided while withdrawing itfrom the liquid phase, if no decomposition or polymerizationof
11、the test liquid occurs on vaporization, and if the vapor of thetest liquid does not react with the walls of the sample containeror connecting lines. It is also necessary that both the test gasand the vapor of the test liquid behave nearly ideally at 101 kPa(1 atm). If the above requirements are met,
12、 this test method willgive estimates of solubility with an accuracy of 62%.5. Significance and Use5.1 The solubility of fixed gases in liquids is an importantengineering parameter in the design of hydraulic systems. It isa measure of the amount of gas that can be released fromsolution when a system
13、undergoes changes in pressure andtemperature. Theoretical considerations permit approximatevalues of gas solubility to be computed with reasonableaccuracy. Dissolved gases are separated and quantified chro-matographically. The test method is restricted to use withlow-boiling liquid samples.6. Appara
14、tus6.1 Saturator and Sampler System, suitable for the tests oflow-boiling liquids and gases at various pressures and tempera-tures, shown schematically in Fig. 1. The system comprisesfour parts:6.1.1 High-Pressure Test Chamber, with internal capacity ofapproximately (1 L) such as shown in Fig. 2. Th
15、e lid of the testchamber is equipped with three ports. The first is to contain a1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.11 on Engineering Sciences of High Performance Fluids and Solids.C
16、urrent edition approved May 1, 2007. Published June 2007. Originallyapproved in 1975. Last previous edition approved in 2002 as D 3429 93 (2002)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandard
17、s volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.thermocouple well, the second is for the addition of the testliquid and pressurization of the syste
18、m with the test gas, andthe third port is for withdrawal of the sample of solution fromthe liquid phase by means of an eductor tube which extends tothe bottom of the chamber. The high-pressure assembly ismounted so that an oscillating motion in a horizontal plane canbe applied to it mechanically wit
19、h a frequency of 1 Hz (onecycle per second) and an amplitude of 0.02 m. Loops (pigtails)are formed in the connecting metal lines to the test chamber toavoid undue stress.6.1.1.1 An electric motor geared down to provide a shaftspeed of about 60 rpm is convenient for providing thenecessary agitation.
20、An eccentric or connecting rod from themotor shaft to the support rod imparts an oscillating motion.Without agitation an excessive time is required for equilibriumto be established.6.1.2 Nitrogen Vapor Cryostat, with suitable temperaturemeasurement and control devices, to provide the low-temperature
21、 environment for the high-pressure test chamber.The cryostat consists of a cylindrical stainless steel Dewar orother suitable insulated container not less than 0.3 m in insidediameter and approximately 0.5 m in inside depth. A solenoidvalve is used to admit liquid nitrogen to the cryostat. The liqui
22、dnitrogen cools the cryostat and its contents. The liquid nitrogen(WarningSee 7.1.) should be introduced through a diffuser,or in a fine stream behind a sheet metal baffle, so that liquiddoes not impinge directly on the test chamber or the controllerthermocouple. The latter may be attached loosely t
23、o the side ofthe test chamber for convenience, but good thermal coupling tothe chamber must not be made. Although the nitrogen vaporcryostat can undergo temperature excursions of several de-grees, the test chamber will stabilize at a temperature thatvaries by only a few tenths of a degree because of
24、 its thermalinertia. To minimize heat transfer from outside of the apparatusand frost condensation, the top of the cryostat should beloosely covered with a lid of foamed glass or plastic, or othersimilar insulating material. (WarningExtremely cold. Lib-erates gas that can cause suffocation. Contact
25、with skin causesburns or freezing, or both. Vapors can react violently with hotmagnesium or aluminum alloys. See A1.1.)6.1.3 Vacuum and Pressurization Manifold, required forinitial evacuation of the test chamber, filling the chamber withthe test liquid, and pressurizing the chamber with the test gas
26、to the desired total pressure. The manifold is shown on the leftside of Fig. 1.6.1.3.1 The burst disk shown in Fig. 1 shall be of the typecapable of withstanding an external pressure of 101 kPa (1atm) when the system is evacuated.6.1.3.2 The pump used to evacuate the apparatus shall be agood quality
27、 oil-filled mechanical pump capable of producingNOTE 1All lines and fittings 300 series stainless steel.1. VI through V8Stainless 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
28、range from 0 to 30 in. Hg and a gage pressure from 0 to2. T/C-1Copper-constantan thermocouple, test liquid temperature. 103 kPa (0 to 15 psi).3. T/C-2Copper-constantan thermocouple, vapor cryostat temperature con- 6. Burst DiskSelect to release at 50 % higher than maximum desired systemtroller. pres
29、sure4. G-1Bourdon gage, 412 or 6-in. size, Grade 3A (accuracy 60.25 % of 7. Temperature ControllerRange 77 to 300 K, accuracy 60.5 % full rangemaximum reading), range 1.5 times highest desired system pressure. 8. LLoops in stainless steel lines for flexibility.5. G-2Bourdon gage, 312 to 6-in. size,
30、Grade A or B (accuracy 2 % or better 9. R1 and R2Gas pressure regulators with pressure gage.FIG. 1 Saturator ApparatusSchematicD 3429 93 (2007)2an ultimate vacuum of 0.1 Pa (106atm) or better. If conden-sible vapors or reactive vapors are to be pumped, the pumpshall be protected by a suitable absorb
31、er or cold trap.The pumpshall run continuously for the duration of the test.6.1.4 Solution-Sampling SystemThis system utilizes a3-mm (18-in.) outside diameter heavy-wall stainless steeleductor tube extending nearly to the bottom of the testchamber. The eductor tube end extending outside the chamberi
32、s connected to a valve just above the top of the cryostat, andthe outlet of this valve leads to a sample cylinder or containerof about 100-mL volume. Each time a sample is withdrawnfrom the liquid phase, the eductor tube and sampling valvemust be purged, otherwise the liquid and vapor in the line wi
33、llnot necessarily be of equilibrium composition. To reduce theamount of liquid lost through purging, the sample valve (V8 inFig. 1) should be modified to reduce liquid holdup to aminimum. The details of this modification are shown in Fig. 3.6.2 Gas Chromatograph, required for determination of thegas
34、 concentration in the sample. It must be equipped with a gassampling valve. It is desirable that two different size loops beprovided so that the sample size can be adjusted depending onthe concentration of test gas to be determined. Sample loops of0.5 and 2.0 mL are recommended. The gas chromatograp
35、hsystem must permit easy and rapid change of carrier gas andcolumns to suit a wide variety of analytical requirements. Athermal conductivity detector of the glass-coated bead type isrecommended. The instrumentation should provide a variableattenuator for the detector signal so that a wide range of f
36、ixedgas concentrations may be accommodated. A suitable chartrecorder, preferably equipped with integrator, should be pro-vided. Alternatively, a digital readout may be used. A typicalgas chromatograph is shown schematically in Fig. 4, and itspower supply is shown in Fig. 5.NOTE 1Practice E 260 provi
37、des further description.6.3 Leak TestingAll parts of the system should be testedwith helium for leakage at a pressure 1.5 times test operatingpressure and vacuum leak tested. The test should includeexternal leaks and port-to-port leaks in valves. The total systemmaximum acceptable leak rate is 0.1 s
38、td cm3atm/s. A massspectrometer leak detector is suitable for the leak rate mea-surements.7. Reagents and Materials7.1 Calibration MixturesGas ChromatographyFor thedetermination of nitrogen solubility, one or more mixtures ofnitrogen in helium are required for calibration of the gasNOTE 1All materia
39、l 300 series stainless except flange gasket. Design of perforated baffles not critical but leave 6-mm diameter holes spaced on20-mm centers are recommended. Baffles should be spot-welded to the inside of the chamber to prevent movement. The purpose of the baffles is toincrease turbulence in the liqu
40、id and thereby increase the rate of solubility of gas in the test liquid.NOTE 2The conflat flange manufactured by the Varian Corp. of Palo Alto, CA, is suitable.FIG. 2 Test Chamber DetailD 3429 93 (2007)3chromatograph. Concentrations of 2 % and 10 % are recom-mended. The exact concentration of each
41、mixture must beaccurately known to 61 % of the absolute concentration of theminor constituent. Certified calibration mixtures are availablefrom suppliers of commercial cylinder gases. For the determi-nation of helium solubilities, mixtures of helium in nitrogencontaining about 0.2 % and 1.0 % helium
42、 are recommended.The exact concentration should be known to 61 % of theabsolute mole fraction of the helium concentration. Nitrogen isused as the carrier gas when helium is the gas whose solubilityis to be determined. Helium is used as the carrier gas whennitrogen solubility is being determined. (Wa
43、rningCompressed gas under high pressure. Gas reduces oxygenavailable for breathing. See A1.2.)7.2 Column MaterialsBecause only two-component sys-tems are analyzed and the boiling points of the test gas andliquid are relatively far apart, a relatively short column issufficient to provide resolution.
44、For most test liquids, a 0.2-mcolumn of silica gel or molecular sieve will separate the testgas and test liquid. The column should be constructed of 6-mm(0.25-in.) thin-walled stainless steel tubing. Certain reactivetest liquids, particularly the powerful oxidizers that containfluorine, may react wi
45、th the stationary phase materials toproduce interferences. If this is the case, more elaboratecolumns must be used to afford resolution. Each combinationof gas and liquid poses its own particular analytical problemand a certain amount of experimentation with stationary phasematerials may be required
46、. Table 1 contains a list of materialsfound appropriate for some typical test gas/liquid combina-tions.7.3 Gases, CompressedHigh-purity helium and nitrogen,or other test gases, are required for saturating the test liquids.The same gases are required for carrier gases in the gaschromatograph. (Warnin
47、gsee 7.1.)NOTE 1Stainless steel wire extends from the position shown in the valve to the lower end of the eductor tube. The purpose of this modification isto 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 ser
48、vice.FIG. 3 Sampling Valve (V8) ModificationFIG. 4 Gas Chromatograph SchematicD 3429 93 (2007)48. Safety Precautions8.1 This procedure is applicable to determination of solu-bilities of gases in highly reactive or flammable test liquids athigh pressure under cryogenic conditions. It is mandatory tha
49、tadequate safety precautions be employed. All parts of systemsat high pressure must be provided with suitable barricades toprevent injury to operating personnel in the event of rupture ofthe equipment, and the portion of the eductor tube which isoutside of the test chamber must be used in an explosion-proofhood.9. Procedure9.1 Evacuate the test chamber and the transfer manifold byopening the vacuum valve V3 (Fig. 1).9.2 Set the temperature controller and cool the cryostat to atemperature near the temperature at which the solubilitymeasurement i
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