ASTM E563-2008 866 Standard Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature《作为参考温度制备和使用的冰点浴的标准实施规程》.pdf

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1、Designation: E 563 08Standard Practice forPreparation and Use of an Ice-Point Bath as a ReferenceTemperature1This standard is issued under the fixed designation E 563; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las

2、t revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers a method of preparing, maintaining,and using a temperature reference bath of a mixture of shavedice

3、and water, saturated with air at a pressure of 101 325 Pa (1atm).1.2 An industrial practice for relating values referenced tothe ice point and to the water triple point on the ITS-90 isincluded.1.3 Methods to promote uniformity of bath temperature bymechanical stirring or agitation are not described

4、 in detail.1.4 Methods of approximating the ice point, as bythermostatically-controlled refrigeration, are not covered bythis practice.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to est

5、ablish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterE 344 Terminology Relating to Thermometry and Hydrom-etryE 1594 Guide for Expression of Temperature

6、3. Terminology3.1 DefinitionsDefinitions given in Terminology E 344,unless otherwise defined herein, apply to terms as used in thispractice.3.2 Temperature relationships given in Guide E 1594, un-less otherwise defined herein, apply to temperature values asused in this practice.3.3 Definitions of Te

7、rms Specific to This Standard:3.3.1 ice-point bath, nphysical system containing ice andwater assembled to realize the ice point as a referencetemperature, or to establish a constant temperature near 0 C.4. Summary of Practice4.1 The ice-point bath described by this practice consists ofan intimate mi

8、xture, without voids, of pure shaved ice or iceparticles and distilled air-saturated water in a thermally insu-lating vessel open to the atmosphere.4.2 The ice bath realization of the ice point physicallyapproximates, with small uncertainty, a natural fixed-pointtemperature.4.2.1 An ice-point bath p

9、repared by rigorous application ofthis practice, using distilled-water ice and air-saturated, chilleddistilled water, typically has a temperature of 0.000 6 0.002 Cat a barometric pressure of 101,325 Pa (1 standard atmo-sphere). See 8, Precision and Bias.4.2.2 The ice-point bath is open to the atmos

10、phere. Thesolubility of air in water, which affects phase change, is directlyproportional to the atmospheric pressure. The effect of baro-metric pressure on the ice point is 75 nK/Pa (7.6 mK/atm).Accordingly, the change in ice-point temperature resultingfrom an increase in elevation above sea level

11、is -0.86 mK per1000 m increase in altitude (-0.26 mK per 1000 ft increase inaltitude). See Table 1.4.3 The ice-bath temperature can also be measured with anaccurately calibrated thermometer or compared to a watertriple point cell and the bath temperature reported as themeasured temperature with an u

12、ncertainty that is attributed tothe measurement, not to the ice point.5. Significance and Use5.1 This practice is adequate for use with other ASTMstandards that specify the ice point as a reference. It is alsointended to be adequate for most other ice-point referencepurposes.1This practice is under

13、the jurisdiction ofASTM Committee E20 onTemperatureMeasurement and is the direct responsibility of Subcommittee E20.07 on Funda-mentals in Thermometry.Current edition approved Nov. 1, 2008. Published December 2008. Originallyapproved in 1976. Discontinued February 1996 and reinstated in 1997 asE 563

14、 97. Last previous ediiton approved in 2002 as E 563021.2For referenced ASTM standards, visit the 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.1Copy

15、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 The ice point is a common practical industrial referencepoint of thermometry. The ice point is relatively simple torealize and provides a readily available natural fixed-pointreference t

16、emperature.5.3 Use in Resistance Thermometry:5.3.1 The ice point was a defining fixed point on practicaltemperature scales prior to 1960.5.3.2 The ITS-90 defines W(T90) = R(T90)/R(273.16 K), themeasured resistance ratio of a Standard Platinum ResistanceThermometer (SPRT), in reference to the water t

17、riple point, notthe ice point (1).3In many instances, where the water triplepoint is not available, or when the accuracy obtainable with thewater triple point is not required, reference to a properlyestablished and maintained ice-point reference is used. Forindustrial-quality resistance thermometers

18、, the resistance valueis determined for 0 C, and an uncertainty that is appropriatefor the quality of the ice-point realization is assigned.5.4 Use in Thermoelectric Thermometry:5.4.1 In thermoelectric thermometry, the ice point is ordi-narily used as the reference temperature (2).5.4.2 Adequate the

19、rmoelectric reference requires that ther-mocouple junctions be well-coupled thermally to the bath,electrically isolated from each other and from the bath, andadequately immersed to avoid perturbing the reference-junction temperatures by radiation and longitudinal conductionof heat along the thermoel

20、ements (3 and 4).5.5 Use in Liquid-in-Glass Thermometry:5.5.1 In liquid-in-glass thermometry, the ice point is ordi-narily used as the reference temperature (6).5.5.2 The periodic recalibration of a liquid-in-glass ther-mometer at the ice point provides a reliable indication of theeffect of gradual

21、relaxation of residual mechanical strains in theglass that have a significant effect on the volume of the bulb(6).6. Hazards6.1 Excess water accumulating in any region, particularlyaround the reference location, can elevate the temperature inthat vicinity above the ice point. Errors, usually somewha

22、t lessthan 4 C, can occur from this cause in poorly maintained bathsand with poorly positioned test objects (3 and 4).6.2 For a stirred bath, the temperature of the bath willdepend on the heat gained by the bath, the amount of water andice, and the vigor of stirring. The uniformity of temperature of

23、the bath can be enhanced by slowly stirring or agitating theslush of ice and water either manually or by a powered stirringmeans so that all of the ice and water in the bath come intointimate contact.6.3 Ice making machines operate below 0 C. Therefore,when excessively large ice particles are used t

24、o prepare theice-point bath, the initial temperature of the bath can briefly beslightly below the ice point.Also, some of the water may freezeand bridge some of the particles. Use of the bath must bedelayed long enough to establish thermal equilibrium, and theparticles shall be sufficiently small so

25、 that the bath approachesthe required state of ice and air-saturated water in intimatecontact.6.4 Cleanliness is essential as small amounts of dissolvedsalts, and other contaminants can cause the equilibrium tem-perature to be below that of the ice-point temperature.7. Procedure7.1 In the practical

26、use of the ice-point bath, two objectivesshall be accomplished: (1) the bath shall be established andmaintained so that its temperature is a good approximation tothat of the ice point, and (2) the object for which the referencetemperature is to be obtained shall be in thermal equilibriumwith the wat

27、er-ice equilibrium temperature (water-ice interfacetemperature).7.2 Establishing the Ice-Point:7.2.1 All equipment that comes in contact with the waterand ice of an ice-point bath shall be clean. Thoroughly rinse theequipment with tap water, then rinse with the type of waterused for the ice-point ba

28、th medium. Use clean plastic gloves tohandle the ice and equipment.7.2.2 Use water of purity equivalent to or better than type IVreagent water, Specification D 1193, for the ice-point bathmedium. Chill a quantity of the water to near 0 C in a flaskand shake vigorously to aerate the water. Freeze ano

29、therportion of the water to produce ice for the bath.7.2.3 Prepare finely divided ice by shaving or crushing.Shaved ice resembling snow is preferred, but crushed ice isacceptable if the particles are small (not exceeding 2 to 3 mmin diameter).7.2.4 Prepare the bath in a clean thermally insulated ves

30、sel,preferably a wide-mouthed Dewar vacuum flask fitted with aninsulating closure such as a stopper. The vessel should be largeenough that its size does not affect the water-ice equilibriumtemperature and of such diameter and depth that in thermalequilibrium the test objects will not significantly m

31、odify thetemperature of the bath over the region to which the ice pointis to be applied. For usual applications, a diameter of at least 70mm and a depth of at least 300 mm may be adequate.7.2.5 Alternately add shaved ice and chilled water to thevessel, using enough water to saturate the ice but not

32、enough tofloat it. As the vessel fills, compress the ice-water mixture toforce out excess water. The objective is to surround eachparticle of ice with water, filling all voids, but to keep the iceparticles as close together as possible. Continue adding ice andwater and compressing until the vessel i

33、s filled to the requiredlevel. Decant or siphon off excess water.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.TABLE 1 Change in Ice Point Temperature Corresponding toElevation Above Sea LevelElevation Change in ice point, mKSea Level 0500 m (1640 ft

34、) 0.431000 m (3281 ft) 0.861500 m (4921 ft) 1.292000 m (6562 ft) 1.722500 m (8202 ft) 2.153000 m (9843 ft) 2.58E5630827.2.6 Cover the ice-point bath to protect it. Use an opaqueand thermally insulating cover or stopper that is suitable for theapplication.Allow the bath and vessel to equilibrate for

35、at least30 min before using.7.3 Using the Ice-Point Bath:7.3.1 Form a well in the ice-point bath that has the diameterand intended immersion depth of the test object.7.3.2 Cool the test object in water less than 3 C beforeimmersing it in the bath. This reduces the time to reachequilibrium at the ice

36、 point. Pre-cooling the sensor helps topreserve the bath at the ice point for a prolonged time and helpsensure that the water-ice interface will be in contact with thethermometer because negligible melting will occur to increasethe water film thickness.7.3.3 Insert the test object with the sensor po

37、rtion of theobject, such as the sensing element of an SPRT, to a depth ofat least ten object diameters below the surface. For thermo-electric thermo-elements of high thermal conductivity, as muchas 200 mm immersion may be necessary. For total immersionliquid-in-glass thermometers, immerse to the 0 C

38、 (32 F)mark. For partial immersion liquid-in-glass thermometers,immerse to the immersion line or stated immersion depth.Keep the sensor portion of the object several centimeters abovethe bottom of the flask to avoid the zone at the bottom wheredenser melt water tends to accumulate.7.3.4 Close the to

39、p of the vessel around the test object withan opaque insulating stopper or other thermal barrier to reduceheat transfer through the surface of the bath.NOTE 1When liquid-in-glass thermometers are tested in an ice pointbath, the bath may be left uncovered. The loss of precision between acovered and u

40、ncovered bath may be below the resolution of liquid-in-glassthermometers. The user must test for this condition.7.3.5 Allow the bath and test object to come to thermalequilibrium.7.4 Maintaining the Bath:7.4.1 As ice particles in the bath melt, excess water beginsto accumulate. This melt water has a

41、 temperature slightlywarmer than 0 C. Since the density of water is at a maximumat 4 C, the slightly warm melt water will collect at the bottomof the bath and, hence, around the test object. Under theseconditions, the bath will no longer be at 0 C and cannot serveas an ice-point bath. For this reaso

42、n surplus water should beremoved, as it accumulates, from the bottom of the bath bydecanting or siphoning. The presence of excess water can bedetected if water overspill occurs when the ice is depressed.Add ice particles, and chilled water, as necessary so that the iceslush column always extends to

43、at least 30 mm below thelowest point of the test object.7.4.2 In order to sustain the ice point over prolongedperiods, the ice-point bath may be immersed in another baththat is kept near 0 C.8. Precision and Bias8.1 If a succession of ice-point baths is prepared by follow-ing all of the procedures d

44、escribed in this practice, routinedetermination of the temperature of each of the baths with astable, well-calibrated standard platinum resistance thermom-eter will yield values of temperature that vary over a range ofabout 4 mK with a sample standard deviation of about 1 mK(5).8.2 The variability r

45、epresents the reproducibility of the icepoint under the conditions of this practice, and the standarddeviation may be interpreted as a measure of the imprecision ofrealizing an ice point.8.3 The mean of values determined under the conditions of8.1 will be biased from 0 C by an amount negligible comp

46、aredto the variability (5).8.4 An ice-point bath prepared by rigorous application ofthis practice may be assigned a temperature of 0 C with anexpanded total uncertainty (k = 2) of about 2 mK (5).8.5 Sources of Error and Uncertainty:8.5.1 The temperature of a poorly made or poorly main-tained ice-poi

47、nt bath can differ from 0 C by as much as severalkelvins. Impurities in the water usually lower the temperature.Excessive water in the bath can cause an increase in tempera-ture as denser warm water settles to the bottom. Large chunksof very cold ice added to a bath can produce local temperaturedepr

48、ession.8.5.2 Type IV grade reagent water prepared with differentapparatus can produce ice-point baths with slightly differenttemperatures that are detectable with very precise thermom-etry. Temperature differences of 0.4 mK have been observed inice-point baths made from water purified in different s

49、tills (5).8.5.3 The temperature of an ice-point bath made withtypical potable city tap water may be low by 10 to 20 mK (3,5).8.5.4 The temperature of the ice-point bath is slightlydependent on pressure. The temperature is lowered by about6.3 K for each centimeter of depth below the liquid surfacedue to hydrostatic pressure. There is a corresponding effect forchanges in atmospheric pressure. In most cases, pressureeffects can be ignored (4).8.5.5 In an ice-point bath, the actual temperature of a pointin an immersed test object that conducts heat into the