1、Designation: D2879 10D2879 18Standard Test Method forVapor Pressure-Temperature Relationship and InitialDecomposition Temperature of Liquids by Isoteniscope1This standard is issued under the fixed designation D2879; the number immediately following the designation indicates the year oforiginal adopt
2、ion or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense
3、.1. Scope Scope*1.1 This test method covers the determination of the vapor pressure of pure liquids, the vapor pressure exerted by mixtures ina closed vessel at 4040 % 6 5 % ullage, and the initial thermal decomposition temperature of pure and mixed liquids. It isapplicable to liquids that are compa
4、tible with borosilicate glass and that have a vapor pressure between 133 Pa (1.0 torr) and 101.3kPa (760 torr) 133 Pa (1.0 torr) and 101.3 kPa (760 torr) at the selected test temperatures. The test method is suitable for use overthe range from ambient to 748 K. 623 K. The temperature range may be ex
5、tended to include temperatures below ambient provideda suitable constant-temperature bath for such temperatures is used.NOTE 1The isoteniscope is a constant-volume apparatus and results obtained with it on other than pure liquids differ from those obtained in aconstant-pressure distillation.1.2 Most
6、 petroleum products boil over a fairly wide temperature range, and this fact shall be recognized in discussion of theirvapor pressures. Even an ideal mixture following Raoults law will show a progressive decrease in vapor pressure as the lightercomponent is removed, and this is vastly accentuated in
7、 complex mixtures such as lubricating oils containing traces of dewaxingsolvents, etc. Such a mixture may well exert a pressure in a closed vessel of as much as 100 times that calculated from its averagecomposition, and it is the closed vessel which is simulated by the isoteniscope. For measurement
8、of the apparent vapor pressurein open systems, Test Method D2878, is recommended.1.3 The values stated in SI units are to be regarded as the standard.The values given in parentheses are for information only.afterSI units are provided for information only and are not considered standard.1.4 WARNINGMe
9、rcury has been designated by many regulatory agencies as a hazardous materialsubstance that can causecentral nervous system, kidney and liver damage. serious medical issues. Mercury, or its vapor, may has been demonstrated to behazardous to health and corrosive to materials. Caution should be taken
10、Use Caution when handling mercury and mercurycontaining mercury-containing products. See the applicable product Material Safety Data Sheet (MSDS) for details and EPAswebsitehttp:/www.epa.gov/mercury/faq.htmfor additional information. Users should be aware (SDS) for additional informa-tion. The poten
11、tial exists that selling mercury or mercury containing products into your state or country may be prohibited bylaw.mercury-containing products, or both, is prohibited by local or national law. Users must determine legality of sales in theirlocation.1.5 This standard does not purport to address all o
12、f the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use. For specific warning statements, see 6
13、.10, 6.12, and Annex A2.1.6 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization
14、Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D2878 Test Method for Estimating Apparent Vapor Pressures and Molecular Weights of Lubricating Oils1 This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubrica
15、nts and is the direct responsibility of SubcommitteeD02.L0.07 on Engineering Sciences of High Performance Fluids and Solids (Formally D02.1100).Current edition approved Oct. 1, 2010Dec. 1, 2018. Published October 2010December 2018. Originally approved in 1970. Last previous edition approved in 20072
16、010as D2879 97D2879 10.(2007). DOI: 10.1520/D2879-10. 10.1520/D2879-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the AST
17、M website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult
18、 prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA
19、 19428-2959. United States1E230 Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 ullagethat percentage of a closed system which is filled with vapor.3.1.1.1 DiscussionSpecifically, on F
20、ig. 1, that portion of the volume of the isoteniscope to the right of point A whichthat is filled with vapor.FIG. 1 IsoteniscopeD2879 1823.2 Symbols:C = temperature, C,K = temperature, K,p = pressure, Pa or torr,Pe = experimentally measured total system pressure,Pa = partial pressure due to fixed ga
21、ses dissolved in sample,Pc = corrected vapor pressure, Pa or torr.t = time, s,K5C1273.15 (1)4. Summary of Test Method4.1 Dissolved and entrained fixed gases are removed from the sample in the isoteniscope by heating a thin layer of a sampleat reduced pressure, removing in this process the minimum am
22、ount of volatile constituents from the sample.4.2 The vapor pressure of the sample at selected temperatures is determined by balancing the pressure due to the vapor of thesample against a known pressure of an inert gas. The manometer section of the isoteniscope is used to determine pressure equality
23、.4.3 The initial decomposition temperature is determined from a plot of the logarithm of the vapor pressure versus the reciprocalof absolute temperature. The initial decomposition temperature is taken as that temperature at which the plot first departs fromlinearity as a result of the decomposition
24、of the sample. An optional method provides for the use of isothermal rates of pressurerise for this purpose (see Annex A1). These are measured at several temperatures and the logarithm of the rate of pressure rise isplotted versus the reciprocal of absolute temperature. The decomposition temperature
25、 of the sample is taken to be that temperatureat which the rate of increase of pressure is sufficient to produce a rise of 185 Pa 185 Pa (0.0139 torr(0.0139 torr/s).s).NOTE 2Vapor pressures less than 133 Pa (1.0 torr), 133 Pa (1.0 torr), but greater than 13.3 Pa (0.1 torr) 13.3 Pa (0.1 torr) at a se
26、lected test temperaturecan be determined directly with reduced accuracy. In some cases the tendency of the sample to retain dissolved or occluded air may prevent directdeterminations of vapor pressure in this range. In such cases, data points obtained at higher pressures can be extrapolated to yield
27、 approximate vaporpressures in this range.5. Significance and Use5.1 The vapor pressure of a substance as determined by isoteniscope reflects a property of the sample as received including mostvolatile components, but excluding dissolved fixed gases such as air. Vapor pressure, per se, is a thermody
28、namic property whichis dependent only upon composition and temperature for stable systems. The isoteniscope method is designed to minimizecomposition changes which may occur during the course of measurement.6. Apparatus6.1 Isoteniscope (Fig. 1).6.2 Constant-Temperature Air Bath(Fig. 2) for use over
29、the temperature range from ambient to 748 K, 623 K, controlled to62 K 62 K in the zone occupied by the isoteniscope beyond point “A” (Fig. 1).6.3 Temperature Controller.6.4 Vacuum and Gas Handling System (Fig. 3).6.5 Pressure Measurement InstrumentationPressure transducers of suitable ranges are the
30、 preferred means for themeasurement of pressure in the gas handling system. Alternatively bourdon-type vacuum gauges or liquid manometers may beused. Note that more than one gauge or transducer may be required for use over the range of 2.00 kPa (15 torr) to 101 kPa (760torr) 2.00 kPa (15 torr) to 10
31、1 kPa (760 torr) for pressures.6.6 McLeod Vacuum Gauge0 to 2.00 kPa (0 to 15 torr), 0 kPa to 2.00 kPa (0 torr to 15 torr), vertical primary standard type.6.7 Mechanical Two-Stage Vacuum Pump.6.8 Direct Temperature Readout, either potentiometric or electronic.6.9 Thermocouplein accordance with Americ
32、an National Standard for Temperature Measurement Thermocouples (ANSIC96.1) from Specification and Temperature Electromotive Force Tables E230.6.10 Nitrogenpre-purified grade. (WarningCompressed gas under high pressure. Gas reduces oxygen available forbreathing. See A2.1.)6.11 Nitrogen Pressure Regul
33、ator single-stage, 00 kPa to 345 kPa 345 kPa gauge (0(0 psig to 50 psig).50 psig).6.12 Alcohol Lamp(WarningWarningFlammable.Flammable. Denatured alcohol cannot be made nontoxic. See A2.2.)D2879 1837. Hazards7.1 The apparatus includes a vacuum system and a Dewar flask (constant temperature air bath)
34、that is subjected to elevatedtemperatures. Suitable means should be employed to protect the operator from implosion of these systems. These means includewrapping of vacuum vessels, use of safety shield in front of Dewar flask, and use of safety glasses by the operator.8. Procedure8.1 Add to the isot
35、eniscope a quantity of sample sufficient to fill the sample bulb and the short leg of the manometer section(WarningWarningPoison.Poison. Can be harmful or fatal if inhaled or swallowed. Vapor harmful; emits toxic fumes whenheated. Vapor pressure at normal room temperature exceeds threshold limit val
36、ue for occupational exposure. See A1.1.) to pointA of Fig. 1. Attach the isoteniscope to the vacuum system as shown in Fig. 3, and evacuate both the system and the filledA Dewar, strip silvered, 110 mm ID by 400 mm deep.B Borosilicate glass tube, 90 mm OD by 320 mm long.C Glass rod, 18-in. in diamet
37、er by 310 mm long. Three of these heater ele-ment holders are fused along their entire length to the outer surface of TubeB at 120-deg intervals. Slots cut into the fused glass rods on 38-in. centersserve as guides for the heating wire D.C Glass rod, 18 in. in diameter by 310 mm long. Three of these
38、 heater elementholders are fused along their entire length to the outer surface of Tube B at120 deg intervals. Slots cut into the fused glass rods on 38 in. centers serveas guides for the heating wire D.D Resistance wire, B. and S. No. 21 gauge, spirally wrapped around Tube Band its attached guides.
39、E Glass wool pad.F Glass wool pad for centering Tube B and sealing annular opening.G Lower plate of insulated isoteniscope holder.Transite disk 18 in. thick, loose fit in Tube B.Transite disk 18 in. thick, loose fit in Tube B.With hole for isoteniscope.H Upper plate of insulated isoteniscope holder.
40、Transite disk 18 in. thick, loose fit in Dewar A.Transite disk 18 in. thick, loose fit in Dewar A.With hole for isoteniscope.J Glass wool insulation between plates G and H.K Plate spacer rods.L Heater leads connected to power output of temperature controller.T1 Temperature-control thermocouple affix
41、ed to inside wall of Tube B.T2 Temperature-indicating thermocouple affixed to isoteniscope.FIG. 2 Constant-Temperature Air BathD2879 184isoteniscope to a pressure of 13.3 Pa (0.1 torr) 13.3 Pa (0.1 torr) as measured on the McLeod gauge. Break the vacuum withnitrogen (WarningWarningCompressedCompress
42、ed gas under high pressure. Gas reduces oxygen available for breathing. SeeA1.2.). Repeat the evacuation and purge of the system twice to remove residual oxygen.8.2 Place the filled isoteniscope in a horizontal position so that the sample spreads out into a thin layer in the sample bulb andmanometer
43、 section. Reduce the system pressure to 133 Pa (1 torr). 133 Pa (1 torr). Remove dissolved fixed gases by gentlywarming the sample with an alcohol lamp until it just boils (WarningWarningFlammable.Flammable. Denatured alcoholcannot be made nontoxic. See A2.2.). Continue for 1 min.1 min.NOTE 3During
44、the initial evacuation of the system, it may be necessary to cool volatile samples to prevent boiling or loss of volatiles.NOTE 4If the sample is a pure compound, complete removal of fixed gases may readily be accomplished by vigorous boiling at 13.3 Pa (0.1 torr).13.3 Pa (0.1 torr). For samples tha
45、t consist of mixtures of substances differing in vapor pressure, this procedure is likely to produce an error due to theloss of volatile components. Gentle boiling is to be preferred in such cases. The rate of boiling during degassing may be controlled by varying both thepressure at which the proced
46、ure is carried out and the amount of heating. In most cases, satisfactory degassing can be obtained at 133 Pa (1 torr). 133 Pa(1 torr). However, extremely viscous materials may require degassing at lower pressures. Samples of high volatility may have to be degassed at higherpressures. In the event t
47、hat the vapor pressure data indicate that the degassing procedure has not completely removed all dissolved gases, it may benecessary to apply a correction to the data or to disregard data points that are so affected (see 8.7). The degassing procedure does not prevent the lossof volatile sample compo
48、nents completely. However, the described procedure minimizes such losses, so that for most purposes the degassed sample canbe considered to be representative of the original sample less the fixed gases that have been removed.8.3 After the sample has been degassed, close the vacuum line valve and tur
49、n the isoteniscope to return the sample to the bulband short leg of the manometer so that both are entirely filled with the liquid. Create a vapor-filled, nitrogen-free space betweenthe bulb and the manometer in the following manner: maintain the pressure in the isoteniscope at the same pressure used fordegassing; heat the drawn-out tip of the sample bulb with a small flame until sample vapor is released from the sample; continueto heat the tip until the vapor expands sufficiently to displace part of the sample from the upper part of the
