1、Designation: E1782 14Standard Test Method forDetermining Vapor Pressure by Thermal Analysis1This standard is issued under the fixed designation E1782; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A num
2、ber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes a procedure for the determi-nation of the vapor pressure of pure liquids or melts fromboiling point measurement
3、s made using differential thermalanalysis (DTA) or differential scanning calorimetry (DSC)instrumentation operated at different applied pressures.1.2 This test method may be used for the temperature range273 to 773 K (0 to 500C) and for pressures between 0.2 kPato 2 MPa. These ranges may differ depe
4、nding upon theinstrumentation used and the thermal stability of materialstested. Because a range of applied pressures is required by thistest method, the analyst is best served by use of instrumenta-tion referred to as high pressure differential thermal instrumen-tation (HPDSC or HPDTA).1.3 The valu
5、es stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard. (See also IEEE/ASTM SI 10.)1.4 There is no ISO standard equivalent to this test method.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its
6、 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 Documents2.1 ASTM Standards:2E177 Practice for Use of the Terms Precision and Bias inASTM Test Method
7、sE473 Terminology Relating to Thermal Analysis and Rhe-ologyE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE967 Test Method for Temperature Calibration of Differen-tial Scanning Calorimeters and Differential Thermal Ana-lyzersE1142 Terminology Relatin
8、g to Thermophysical PropertiesE2071 Practice for Calculating Heat of Vaporization orSublimation from Vapor Pressure DataIEEE/ASTM SI 10 Standard for Use of the InternationalSystem of Units (SI) The Modern Metric System3. Terminology3.1 Definitions:3.1.1 The following terms are applicable to this tes
9、t methodand can be found in either Terminology E473 or TerminologyE1142: boiling pressure, boiling temperature, differential scan-ning calorimetry (DSC), differential thermal analysis (DTA),vapor pressure, vaporization point, vaporization temperature.3.2 Symbols:3.2.1 A, B, CAntoine vapor pressure e
10、quation (1)3con-stants (log10, kPa, K):Antoinevaporpressureequation:Log10P 5 A 2 B/T1C!where:P = vapor pressure, kPa, andT = temperature, K.4. Summary of Test Method4.1 A specimen in an appropriate container is heated at aconstant rate within a DTA or DSC instrument operated underan applied constant
11、 vacuum/pressure between 0.2 kPa and 2MPa until a boiling endotherm is recorded. Boiling is observedat the temperature where the specimen partial pressure equalsthe pressure applied to the test chamber. The pressure isrecorded during observation of the boiling endotherm and theboiling temperature is
12、 recorded as the extrapolated onsettemperature. This measurement is repeated using new speci-mens for each of five or more different pressures covering thepressure range of interest. The pressure-temperature data arefitted as Log10P and 1/T (K1) to the Antoine vapor pressureequation (see Fig. 1). Va
13、por pressure values required forspecific reports are then computed from the derived equation.1This test method is under the jurisdiction ofASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on Calo-rimetry and Mass Loss.Current edition approved March 15
14、, 2014. Published April 2014. Originallyapproved in 1996. Last previous edition approved in 2008 as E1782 08. DOI:10.1520/E1782-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informa
15、tion, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to a list of references at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 The capability of
16、the assembled system after calibrationshould be periodically checked by using this method on purewater as a reference substance and comparing the derivedvapor pressure data with the NBS/NRC steam tables attachedas Appendix X1. For pressures below 5 kPa, operation of theassembled system may be checke
17、d using 1-octanol (2).5. Significance and Use5.1 Vapor pressure is a fundamental thermophysical prop-erty of a liquid. Vapor pressure data are useful in processdesign and control, in establishing environmental regulationsfor safe handling and transport, for estimation of volatileorganic content (VOC
18、), and in deriving hazard assessments.Vapor pressure and boiling temperature data are required forMaterial Safety Data Sheets (MSDS). The enthalpy of vapor-ization may also be estimated from the slope of the vaporpressure curve (see Practice E2071).6. Interferences6.1 This test method is limited to
19、materials that exhibit asingle sharp boiling endotherm under the conditions outlined inthis test method.6.2 Oxidation, pyrolysis, or polymerization of condensedorganic materials retained at temperatures above their ambientboiling point may be encountered at the elevated pressures ofthis method. This
20、 will be observed as an exotherm or asignificantly broadened endotherm, or both, and shall not beconsidered a valid pressure-temperature datum point. Use of aninert gas for elevated pressures or for back-filling after evacu-ation of the sample chamber is recommended to minimize therisk of oxidation.
21、6.3 Partial blockage of the pinhole in the DSC containerscould occasionally be encountered. This may be observed asnoise spikes on the boiling endotherm and shall not beconsidered a valid pressure-temperature datum point7. Apparatus7.1 The essential equipment required to provide the mini-mum instrum
22、ent capability of this test method includes (seeFig. 2):7.1.1 Differential Scanning Calorimeter (DSC) or Differen-tial Thermal Analyzer (DTA), consisting of:7.1.1.1 DSC/DTA Test Chamber, composed of a furnace(s)to provide uniform controlled heating of a specimen andreference at a constant rate withi
23、n the 273 to 773 K temperaturerange of this test method; a temperature sensor to provide anindication of the specimen/furnace temperature to 61K;adifferential sensor to detect a difference (temperature or heatflow) between the specimen and reference equivalent to 5 mW;and a means of sustaining an in
24、ert gas or vacuum test chamberenvironment at pressures above and below ambient.FIG. 1 Vapor Pressure Curve with Experimental Data and An-toine Equation FitNOTE 1“A”, DSC/DTA instrument; “B,” pressure transducer; “C,”pressure/vacuum source; “D,” pressure stabilizer; “E,” pressure regula-tor; and “F,”
25、 relief valve.FIG. 2 Schematic of ApparatusE1782 1427.1.1.2 Temperature Controller, capable of executing aspecific temperature program by operating the furnace(s)between selected temperature limits to 61 K at a rate oftemperature change of 5 K/min constant within 61%.7.1.1.3 Recording Device, to pro
26、vide a means of acquiring,storing and displaying measured or calculated signals or both.The minimum output signals are heat flow, temperature andtime.7.1.2 Pressure/Vacuum System, consisting of:7.1.2.1 A pressure vessel, or similar means of sealing thetest chamber at any applied absolute pressure wi
27、thin the 0.2kPa to 2 MPa range of this test method.7.1.2.2 Source of Pressurized Gas, or vacuum capable ofsustaining a regulated inert gas pressure to the test chamber ofbetween 0.2 kPa and 2 MPa.7.1.2.3 Pressure Transducer(s), to measure the pressure inthe test chamber to within 1 % including any t
28、emperaturedependence of the transducer(s) over the range of 0.2 kPa to 2MPa.NOTE 1Distance (or dead volume) between the pressure transducerand the specimen in the test chamber should be minimized to ensureaccurate recording of the pressure at the time of boiling.7.1.2.4 Pressure Regulator, or simila
29、r device to adjust theapplied pressure in the test chamber to 62 % of the desiredvalue.7.1.2.5 Ballast, or similar means to maintain the appliedpressure in the test chamber constant to 61%.7.1.2.6 Valves, to control delivery of the inert gas/vacuum tothe test chamber or to isolate components of the
30、pressure/vacuum system, or both. Valves shall be rated in excess of the2 MPa upper pressure limit of this test method.7.1.3 Containers, (pans, capillary tubes, etc.) that are inertto the specimen and reference materials and which are ofsuitable structural shape and integrity to contain the specimena
31、nd reference in accordance with the following specific re-quirements:7.1.3.1 It is imperative that the containers used in this testmethod be capable of retaining the specimen in a manner thatminimizes sample loss through vaporization prior to boilingand that promotes the development of vapor-liquid
32、equilibriumat boiling. When both conditions are met a sharp endothermwith little or no baseline curvature at the onset will beobserved.NOTE 2Studies byASTM task group E37.01.05 and others (3-5) havedetermined glass cylindrical containers of 2 to 4 mm inside diameter by 25mm long are suitable for the
33、rmocouple inserted style DTA instruments;and a hermetic sealable pan (approximately 40 L vol) with a singlepinhole in the center of the lid is suitable for DSC instruments withnominal heating rates of 5 K/min. Use of a progression of pinhole sizesranging from approximately 50 to 350 m is recommended
34、 in order toretain boiling endotherm sharpness over the full pressure range of thismethod. Typically, the sharpest boiling endotherm for a sample will beproduced at atmospheric pressure with a small (50 to 75 m) pinhole. Aspressure is reduced, increasingly larger pinholes should be used tominimize e
35、ndotherm broadening. Use of large pinholes (350 m) atpressures as low as 0.2 kPa has been shown to produce boiling endothermsof comparable sharpness to atmospheric pressure endotherms. Use ofheating rates other than 5 K/min are not recommended for this testmethod. Higher rates may result in some sel
36、f-pressurization of thespecimen and lesser rates will extend measurement times and will tend topromote preboiling vaporization.7.2 Auxiliary equipment considered useful in conductingthis test method include:7.2.1 Acoolant system that can be coupled directly with thecontroller to the furnace to haste
37、n its recovery from elevatedtemperatures or to sustain a subambient temperature to within61 K of a lower limit temperature.7.2.2 Abalance to weigh specimens or specimen containers,or both, to 60.1 mg.7.2.3 Asyringe or micropipet to deliver liquid specimens of1to5L610 %.7.2.4 Pressure relief valve to
38、 prevent accidental overpres-surization in the pressure system.Arating of 10 % in excess ofthe upper use pressure is suggested provided it does not exceedthe maximum working pressure rating of any individualcomponent in the system.8. Precautions8.1 Safety Precautions:8.1.1 Pressures in addition to a
39、mbient are employed in thistest method. Ensure that the pressure/vacuum system is certi-fied for operation at the extremes of pressure encountered withthis test method. Incorporation of a pressure relief device isrecommended.8.1.2 Adequate provisions shall be available for retentionand disposal of a
40、ny spilled mercury if mercury-containingpressure devices are employed.9. Sampling9.1 Typical specimen sizes used for individual pressuremeasurements are 1 to 5 mg of solid or 1 to 5 L of liquid.Similar size specimens should be used for each individualmeasurement of a given sample.9.2 Samples are ass
41、umed to be tested as received. Reportany special sampling or pretreatment used with this testmethod.10. Calibration10.1 Perform calibration according to Test Method E967,using the heating rate and specimen containers intended for thistest method. Accomplish temperature calibration at ambientpressure
42、.NOTE 3The effect of pressure on the melting temperature of purematerials used to calibrate the temperature axis has been shown to be0.01 K at the maximum pressure of this method (6). The effects ofvacuum on the heat transfer characteristics and subsequent thermal lag ofvarious differential thermal
43、instruments (DSC and DTA) have not beenestablished. From general experiences these effects should not alter thetemperature axis calibration by more than1Kattheminimum pressure ofthis test method.10.2 Calibrate the pressure transducer according to therecommendations of the manufacturer or similar app
44、ropriateprocedure.11. Procedure11.1 Place the specimen and inert reference in suitablecontainers (see 7.1.3) into the test chamber.NOTE 4If hermetic sealable DSC pans with pinholed lids are used,make sure there is no sample material on the outer surfaces of theE1782 143container and that a good herm
45、etic seal is accomplished. Either will resultin preboiling vaporization that at least partially negates the function of thepinhole. Be certain, also, that the pinhole is free of dirt or debris.NOTE 5For DSC vacuum operation, use of a thin layer of conductivepaste between the pan and the furnace is r
46、ecommended to retain sensitivityand resolution.11.2 Seal the test chamber and apply the desired pressure.NOTE 6It is recommended to flush residual oxygen from the testchamber by either purging for several minutes with inert gas or byevacuation and back-filling with inert gas.11.3 Allow the pressure
47、to stabilize and equilibrate the testchamber at a start temperature which shall be at least 30 Kbelow the expected boiling temperature to ensure stabletemperature control and baseline.11.4 Heat the specimen and reference at a constant rate of 5K/min, recording the DSC/DTA curve until the vaporizatio
48、n iscomplete.11.5 Record the absolute pressure in the test chamber at thetime the boiling endotherm is observed.NOTE 7Most pressure gauges report pressure relative to ambientpressure. In such cases, the measured pressure shall be added to orsubtracted from atmospheric pressure measured by a baromete
49、r to obtainabsolute pressure.11.6 Restore the test chamber to ambient conditions uponcompletion of the heating curve.11.7 Repeat 11.1 11.6 with a new specimen at each of fouror more additional pressures throughout the pressure rangecapability of the equipment.NOTE 8A minimum of five measurements at different pressures arerequired for this test method. Additional measurements should improvethe fit of the Antoine vapor pressure equation and reduce the uncertaintyof the Antoine constants used to calculate the vapor pressure curve.12. Calculation12.1 Determine and
