ASTM E1194-2007 Standard Test Method for Vapor Pressure 《蒸气压的标准试验方法》.pdf

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1、Designation: E 1194 07Standard Test Method forVapor Pressure1This standard is issued under the fixed designation E 1194; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates t

2、he year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes procedures for measuring thevapor pressure of pure liquid or solid compounds. Since nosingle technique is available to measure vapor pressur

3、es from1 3 1011to 100 kPa (approximately 1010to 760 torr), twoprocedures are presented.An isoteniscope (standard) procedurefor measuring vapor pressures of liquids from 1 3 101to 100kPa (approximately 1 to 760 torr) is available in Test MethodD 2879. A gas-saturation procedure for measuring vapor pr

4、es-sures from 1 3 1011to 1 kPa (approximately 1010to 10 torr)is presented in this test method. Both procedures are subjects ofU.S. Environmental Protection Agency Test Guidelines.1.2 These two methods were selected to provide data atnormal environmental temperatures (10 to 60C).At least threetempera

5、ture values should be studied to allow definition of avapor pressure-temperature correlation. Values determinedshould be based on temperature selections such that a mea-surement is made at 25C (as recommended by IUPAC) (1),2avalue can be interpolated for 25C, or a value can be reliablyextrapolated f

6、or 25C. Extrapolation to 25C should beavoided if the temperature range tested includes a value atwhich a phase change occurs. Extrapolation to 25C over arange larger than 10C should also be avoided. The testmethods were selected because of their extended range, sim-plicity, and general applicability

7、 (2). Examples of resultsproduced by the gas-saturation procedure during an interlabo-ratory evaluation are given in Table 1. These data have beentaken from Reference (3).1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4

8、This standard does not purport to address all of thesafety problems, if any, associated with its use. It is 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.2. Referenced Docum

9、ents2.1 ASTM Standards:3D 2879 Test Method for Vapor Pressure-Temperature Rela-tionship and Initial Decomposition Temperature of Liquidsby IsoteniscopeE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 U.S. Environmental Protection Agency Test Guidel

10、ines:Toxic Substances Control Act Test Guidelines; Final Rules,Vapor Pressure43. Terminology Definition3.1 vapor pressurea measure of the volatility in units ofor equivalent to kg/m2(pascal) of a substance in equilibriumwith the pure liquid or solid of that same substance at a giventemperature (4).4

11、. Summary of Isoteniscope Method4.1 The isoteniscope method is a relatively simple techniqueto use for vapor pressures of liquids above 0.133 kPa. Theprocedure is fully described in Test Method D 2879.5. Summary of Gas-Saturation Method5.1 Pressures less than 1.33 kPa may be measured using thegas-sa

12、turation procedure (4).5.2 In this test method, an inert carrier gas (for example N2)is passed through a sufficient amount of compound to maintainsaturation for the duration of the test. The compound may becoated onto an inert support (for example glass beads) or it maybe in a liquid or solid granul

13、ar form.The compound is removedfrom the gas stream using a suitable agent (sorbent or cold1This test method is under the jurisdiction of ASTM Committee E47 onBiological Effects and Environmental Fate and is the direct responsibility ofSubcommittee E47.04 on Environmental Fate and Transport of Biolog

14、icals andChemicals.Current edition approved Oct. 1, 2007. Published October 2007. Originallyapproved in 1987. Last previous edition approved in 2001 as E 1194-01.2The boldface numbers in parentheses refer to the list of references at the end ofthis test method.3For referenced ASTM standards, visit t

15、he ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Federal Register, Vol 50, No. 188, 1985, pp. 3927039273.1Copyright ASTM International, 100 Barr Har

16、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.trap). The amount of the test sample collected is then measuredusing gas chromatography or any other sensitive and specifictechnique capable of suitable mass detection limit for theintended purpose.6. Significance and Use6.1 Vap

17、or pressure values can be used to predict volatiliza-tion rates (5). Vapor pressures, along with vapor-liquid parti-tion coefficients (Henrys Law constant) are used to predictvolatilization rates from liquids such as water. These values arethus particularly important for the prediction of the transp

18、ort ofa chemical in the environment (6).7. Reagents and Materials7.1 The purity of the substance being tested shall bedetermined and documented as part of the effort to define thevapor pressure. If available, all reagents shall conform to thespecifications of the Committee on Analytical Reagents of

19、theAmerican Chemical Society.57.2 Every reasonable effort should be made to purify thechemical to be tested. High sample purity is required foraccurate evaluation of vapor pressure using direct mass lossmeasurement.7.3 For the gas-saturation method, the results can be re-ported in terms of the parti

20、al pressure for each component ofthe mixture that is identified and quantified through thetrapping procedure. However, unless the pure componentvapor pressures and the vapor/liquid activity coefficients of thecontaminants are known, the results cannot be interpreted anymore clearly. If the activity

21、coefficient of the major constituentis defined as one ( = 1), the indicated partial pressure andanalytical purity data can be converted to a pure componentvapor pressure.8. Procedures8.1 Isoteniscope ProcedureRefer to Test Method D 2879.8.2 Gas-Saturation Procedure:8.2.1 The test sample can be (1) c

22、oated onto clean silicasand, glass beads, or other suitable inert support from solution;prior to data measurement, the solvent must be completelyremoved by application of heat and flow (2) in solid state,possibly using a method similar to the previous one or bymelting the solid to maximize surface a

23、rea prior to datameasurement; or (3) a neat liquid. If using a coated-supportprocedure, the thickness of the coating must be sufficient toensure that surface energy effects will not impact vaporization.Following volatilization the surface must remain completelycoated with the test compound.8.2.2 Coa

24、t the support prior to column loading, to ensure thesupport is properly coated. Use sufficient quantity of materialon the support to maintain gas saturation for the duration of thetest.8.2.3 Put the support into a suitable saturator container. Thedimensions of the column and gas velocity through the

25、 columnshould allow complete saturation of the carrier gas andnegligible back diffusion.8.2.4 Connect the front and back-up traps to the columndischarge line downstream from the saturator column. Use theback-up trap to check for breakthrough of the compound fromthe front trap. For an example of such

26、 a system, see Fig. 1.8.2.5 Surround the saturator column and traps by a thermo-stated chamber controlled at the test temperature within60.05C or better.8.2.6 If test material is detected in the second trap, break-through has occurred and the measured vapor pressure may betoo low. To eliminate break

27、through, take one or both of thefollowing steps:8.2.6.1 Increase trapping efficiency by using more efficienttraps, such as a larger higher capacity or a different type of trap.8.2.6.2 Decrease the quantity of material trapped by de-creasing the flow rate of carrier gas or reduce the samplingperiod.8

28、.2.7 After temperature equilibration, the carrier gas passesthrough the specimen and the sorbent (or cold) traps and exitsfrom the thermostated chamber. The thermostatically-controlled chamber should utilize liquid baths to facilitate heattransfer. Liquid (for example, ethlene-glycol-water or oil) b

29、athsare suggested because of the difficulty in controlling tempera-tures in accordance with the tight specifications required (7)using air baths. Variations in the ambient temperature infacilities designed for hazardous chemical work make this acritical requirement.8.2.8 Measure the flow rate of the

30、 effluent carrier gas at theadiabatic saturation temperature using a calibrated mass flowmeter bubble meter or other, nonhumidifying devices consid-ered suitable. Check the flow rate frequently during the5“Reagent Chemicals,American Chemical Society Specifications,”Am. Chemi-cal Soc., Washington, DC

31、. For suggestions on the testing of reagents not listed bytheAmerican Chemical Society, see “Reagent Chemicals and Standards,” by JosephRosin, D. Van Nostrand Co., Inc., New York, NY, and the “United StatesPharmacopeia.”TABLE 1 Gas-Saturation Procedure Results Obtained During anInterlaboratory Evalu

32、ationTestCompoundTempera-ture, CMeanVaporPres-sures,kPaStandardDevia-tion Esti-mate, SrASquareRoot,SRBPrecisionEstimate,SRCNaphthalene 25 1.3 3 1020.31 0.39 0.5035 3.5 3 1020.55 1.23 1.35Benzaldehyde 25 1.8 3 1010.31 1.24 1.2835 2.8 3 1010.33 1.12 1.17Aniline 25 7.9 3 1021.9 3.8 4.335 1.5 3 1010.25

33、0.28 0.382-Nitrophenol 25 1.2 3 1020.33 0.41 0.5335 3.2 3 1020.53 1.57 1.66Benzoic Acid 25 1.5 3 1040.32 1.69 1.7235 5.7 3 1042.3 5.2 5.7Phenanthrene 25 1.6 3 1050.36 0.46 0.5835 4.7 3 1052.41 2.39 2.422,4-Dinitrotoluene 25 7.1 3 1051.9 6.3 6.635 2.3 3 1041.0 3.2 3.4Anthracene 25 6.0 3 1063.7 13.8 1

34、4.335 1.1 3 1050.23 2.29 2.30Dibutylphthalate 25 6.8 3 1064.4 8.8 9.835 2.0 3 1050.49 2.28 2.33p,p8-DDT 25 1.7 3 1070.55 1.66 1.7535 5.7 3 10711.1 4.7 12.1ASris the estimated standard deviation within laboratories, that is, an averageof the repeatability found in the separate laboratories.BSRis the

35、square root of the component of variance between laboratories.CSRis the between-laboratory estimate of precision.E1194072procedure to ensure that the total volume of carrier gas isaccurately measured. Use the flow rate to calculate the amountof gas that has passed through the specimen and sorbent or

36、trap. (volume/time) (time) = volume or (mass/time) (time) =mass).8.2.9 Measure the pressure at the outlet of the saturator.Determination of the saturator operating pressure is criticalbecause it will always be above ambient pressure due to apressure drop through the system. Measure either by includi

37、nga pressure gage between the saturator and traps or by deter-mining the pressure drop across the particular trapping systemused in a separate experiment for each flow rate.8.2.10 Calculate the test specimen vapor pressure (which isits partial pressure in the gas stream) from the total gas volume(co

38、rrected to the volume at the temperature at the saturator) andthe mass of specimen vaporized.8.2.11 Record the ambient pressure frequently during thetest to ensure an accurate saturator pressure value. Laboratoriesare seldom at normal atmospheric pressure, and this fact isoften overlooked.8.2.12 Det

39、ermine the time required for collecting the quan-tity of test specimen necessary for analysis in preliminary runsor by estimates based on experience. Before calculating thevapor pressure at a given temperature, carry out preliminaryruns to determine the flow rate that will completely saturate thecar

40、rier gas with sample vapor. To check, determine whetheranother flow rate at the same system temperature gives adifferent calculated vapor pressure.8.2.13 Measure the desorption efficiency for every combi-nation of sample, sorbent, and solvent used. To determine thedesorption efficiency, inject a kno

41、wn mass of sample onto asorbent. Then desorb and analyze it for the recovered mass.8.2.14 For each combination of sample, sorbent and solventused, make triplicate determinations at each of three concen-trations. Desorption efficiency may vary with the concentrationof the actual sample and it is impo

42、rtant to measure theefficiency at or near the concentration of the sample under gassaturation test procedure conditions. It is usually necessary tointerpolate between two measured efficiencies.8.2.15 If the test specimen vapor pressure is very low, checkand make sure significant amounts of the test

43、specimen are notlost on the surface of the apparatus. This is checked by amaterial compatibility test prior to loading the sorbent into thetraps or saturation column. If the tested chemical has asignificant affinity for the traps or saturation column material ofconstruction, select and test an alter

44、native material of construc-tion.8.2.16 When testing elevated temperature conditions, it isnecessary that the system is operating at a uniform tempera-ture. Contaminant condensation on cold spots will give lowvapor pressure values.8.2.17 The choice of the analytical method, trap, anddesorption solve

45、nt depends upon the nature of the test speci-men and the temperature conditions of interest.8.2.18 Advantages of this test method when used with ananalysis specific for the compound of interest are:8.2.18.1 Minor impurities are not likely to interfere witheither the test protocol or the accuracy of

46、the vapor pressureresults, and the effects of impurities on the indicated vaporpressure can be corrected for in the final calculation.FIG. 1 Configuration of Analytical ApparatusE11940738.2.18.2 Pressures of two or more compounds may beobtained simultaneously, providing the compounds do not havesign

47、ificant vapor/liquid activity interaction.9. Alternative Procedures9.1 Although the procedures stated in Section 8 are pre-ferred for vapor pressure measurement at ambient tempera-tures, many laboratories have employed other successful meth-ods. If an alternative is chosen, determine the vapor press

48、ure intriplicate at each of three temperatures and report the averagevalue at each temperature. As stated in 1.2, determine a valueat 25C by direct measurement, interpolation, or reliableextrapolation.10. Calculation10.1 For the gas-saturation procedure, compute the vaporpressure based on the volume

49、 of gas passing through thesaturator and traps and the quantity of chemical removed fromthe saturated gas stream. The calculations involve a series ofequations that convert wet gas flow and mass of organic to thevapor pressure of the chemical in the dry gas at the saturatorcolumn outlet. The equations (7) used for the calculations areas follows:Qw5 qDT! (1)QD5 QwPT2 PH2O!/PT(2)mgas5 QD/22.414273.15 1 texh!/273.15!760!/PT2 PH2O! (3)morg5 Worg/M (4)y 5 morg/mgas(5)P 5 yPT2 PH2O1DP! (6)where:T = elapsed time, min,q = wet gas flow rate, L/m