1、Designation: C729 11Standard Test Method forDensity of Glass by the Sink-Float Comparator1This standard is issued under the fixed designation C729; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、 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 covers the determination of the densityof glass or nonporous solids of density from 1.1 to 3.3 g/cm3.It can be used to deter
3、mine the apparent density of ceramics orsolids, preferably of known porosity.1.2 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 establish appro-priate safety and health practices and determ
4、ine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1217 Test Method for Density and Relative Density (Spe-cific Gravity) of Liquids by Bingham PycnometerE77 Test Method for Inspection and Verification of Ther-mometersF77 Test Method for Apparent
5、 Density of Ceramics forElectron Device and Semiconductor Application33. Summary of Method3.1 The specimen of unknown density is compared with areference standard of known density. The specimen to bemeasured is placed in a test tube containing a solution whosedensity at 35C is within 0.0200 g/cm3of
6、the density of thespecimen at 25C. The solution is prepared using miscibleliquids of known densities bracketing the desired range. Thetube also contains a glass density reference standard whosedensity at 35C is close to that of the solution at 35C; the tubeis immersed in a variable-temperature compa
7、rator bath. Ini-tially the solutions, specimen, and standard are at a temperaturenear 25C, and both the standard and the specimen float in thesolution. The temperature of the system is raised at a uniformrate. Because the volumetric expansion coefficient of thesolution is much higher than those of t
8、he glass pieces, itsdensity decreases more rapidly and eventually both the stan-dard and the specimen will sink (settle) in the solution. Thetemperatures at which the specimen and standard reach themid-point of the test tube are noted and by use of special tables,the density of the specimen is obtai
9、ned.3.2 Range of a Given Density SolutionA given densitysolution can be used to measure specimens whose density iswithin 6 0.0200 g/cm3of the density of the solution at 35C,by operating the comparator bath in the range 25 to 45C.4. Significance and Use4.1 The sink-float comparator method of test for
10、 glassdensity provides the most accurate (yet convenient for practicalapplications) method of evaluating the density of small piecesor specimens of glass. The data obtained are useful for dailyquality control of production, acceptance or rejection underspecifications, and for special purposes in res
11、earch and devel-opment.4.2 Although this test scope is limited to a density rangefrom 1.1 to 3.3 g/cm3, it may be extended (in principle) tohigher densities by the use of other miscible liquids (TestMethod F77) such as water and thallium malonate-formate(approximately 5.0 g/cm3). The stability of th
12、e liquid and theprecision of the test may be reduced somewhat, however, athigher densities.5. Apparatus5.1 Single Tube and Multiple-Tube Comparators (MethodE77)A single-tube comparator can be constructed frommaterials readily available in a typical laboratory, and useful ifone wishes to measure the
13、density of materials within a fairlynarrow range, or if only a few tests need to be run each day.The multiple-tube comparator can be purchased commercially.It is useful if materials with a wide range of density must betested or if many specimens must be tested each day. Thecomparators shall consist
14、of the following:5.1.1 Single-Tube Comparator (Fig. 1):5.1.1.1 Circulating Water Bath, consisting of a 4000-cm3beaker, a cover plate supporting test tubes and thermometer, acooling water coil made from copper tubing, an electrically1This test method is under the jurisdiction of ASTM Committee C14 on
15、 Glassand Glass Products and is the direct responsibility of Subcommittee C14.04 onPhysical and Mechanical Properties.Current edition approved Oct. 1, 2011. Published October 2011. Originallyapproved in 1972. Last previous edition approved in 2005 as C729 05. DOI:10.1520/C0729-11.2For referenced AST
16、M 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.3Withdrawn. The last approved version of this historical standard is referencedo
17、n www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.driven stirrer, and containing an immersion heater with rheostatfor controlling heating rate, or heated by an external heatsource such as a hot plate.5.1.1.2 Test Tubes,
18、two, 100-cm3capacity. The cover platesupports the test tubes, which extended into the water bath.One tube contains the density solution, the test specimen, thestandard, and a glass or TFE-fluorocarbon cage (Fig. 2) thatkeeps the specimens immersed in the solution. The second testtube contains densit
19、y solution and a thermometer; both testtubes employ rubber stoppers for supporting the cage orthermometer.5.1.1.3 Thermometers, two, mercury, readable to 0.1Cbetween 20 and 50C. One thermometer passes through arubber stopper supported by the cover plate into the water bath.The second thermometer pas
20、ses through a rubber stopper intothe test tube that contains density solution only. Thermistors,resistive thermal devices (RTD), or thermocouples capable ofmeasuring and displaying at least 0.1C accuracy between 20and 50C can be used in lieu of mercury thermometers.5.1.2 Multiple-Tube ComparatorThe
21、commercially ob-tainable multiple-tube comparator employs the same principleas the single-tube comparator, except that the multiple-tubeMetric Equivalentsin.1412 1134 29mm 6.4 12.7 25.4 44.4 51 229FIG. 1 Single Tube Sink-Float Density ApparatusC729 112type contains additional specimen tubes. These s
22、pecimen tubesmay contain similar density solutions if a large number ofspecimens with similar density are to be measured; they maycontain density solutions of differing density if a number ofspecimens with a range of densities are to be measured.6. Reagents and Materials6.1 Density Reference Standar
23、dsThe reference standardshall be a solid piece of glass with a volume between 0.10 and0.15 cm3, and a ratio of major to minor dimensions notexceeding 2.0. It shall have a smooth surface and be free ofseeds, cords, and cracks. A quantity of such standards may becut from a 20-g piece of glass similarl
24、y free of defects, withdensity at 25C (r25) known to 60.0001 g/cm3. The density ofsuch a standard glass can be determined to 60.00001 g/cm3bya precise buoyancy method.4Determine the settling tempera-ture of each reference standard to the nearest 0.1C and discardany that deviate more than 0.1C from m
25、ean temperature. Lessprecise density standards are commercially available.6.2 Density SolutionThe following organic liquids5aremixed to provide a solution of the desired density:6.2.1 Isopropyl Salicylate, density (25C) approximately1.10 g/cm3or alpha-bromonaphthalene, density (25C) ap-proximately 1
26、.49 g/cm3.6.2.2 sym-Tetrabromoethane, density (25C) approximately2.96 g/cm3.6.2.3 Methylene Iodide, density (25C) approximately 3.32g/cm3.NOTE 1Methylene iodide, sym-tetrabromoethane, and alpha-bromonaphthalene are light-sensitive. These liquids should be stored inlight-protective containers.Apiece
27、of copper wire in the methylene iodidecontainer will help retard decomposition.6.2.4 The density solution consists of mixtures of isopropylsalicylate and sym-tetrabromoethane for densities between 1.10and 2.96 g/cm3, and of sym-tetrabromoethane and methyleneiodide for densities between 2.96 and 3.32
28、 g/cm3. Properamounts of the two liquids to be used are found by simultane-ous solution of:rsVs5r1V11r2V2(1)Vs5 V11 V2(2)rs5 r1V11r2V2!/V11 V2! (3)where:rs= density of solution density of standard at35C,Vs= volume of solution to be prepared,r1and r2= densities of the component liquids at 35C,andV1an
29、d V2= volumes of the component liquids at 35C.6.2.5 Solution PreparationApproximate volumes of liq-uids required to supply desired density rsare shown in Table1. Mix the two required volumes of liquids 1 and 2 (6.2.4)ina beaker, set on a hot plate, and warm to 35C. Place a densitystandard in the sol
30、ution. Adjust the mixture by adding one ormore drops of either component until the density standardsettles at 35 6 0.2C in the well-stirred solution.7. Preparation of Density-Temperature Tables7.1 Tables are prepared from the equations of this section torelate the specimen density at 25C to its sett
31、ling temperature.These tables are prepared once for each glass referencestandard-density solution system. Subsequent supplies of den-sity solutions prepared for use with the same glass reference4Bowman, H.A., and Schoonover, R. M., “Procedure for High Precision DensityDeterminations by Hydrostatic W
32、eighing,” Journal of Research, National Bureau ofStandards, 71 C, 3, 1967, p. 179.5These liquids are available from most chemical supply companies.FIG. 2 TFE-Flourocarbon Cage for 100-mL Test TubeTABLE 1 Volumes of Liquids for Solutions of Various Densitiesrsg/cm3at 35CVolume of Material Used, cm3Is
33、opropylSalicylatesym-Tetra-bromo-ethaneMethyleneIodide2.103 135 165 .2.136 127 173 .2.190 120 180 .2.222 115 185 .2.236 113 187 .2.257 109 191 .2.291 104 196 .2.315 100 200 .2.335 95 205 .2.363 92 208 .2.403 85 215 .2.434 80 220 .2.448 78 222 .2.473 74 226 .2.495 70 230 .2.511 68 232 .2.529 65 235 .
34、2.560 60 240 .2.589 56 244 .2.596 54 246 .2.619 50 250 .2.633 48 252 .2.669 42 258 .2.702 37 263 .2.728 33 267 .2.757 28 272 .2.812 19 281 .2.847 13 287 .2.863 10 290 .2.893 6 294 .2.933 . 300 12.960 . 277 232.999 . 248 523.035 . 214 863.054 . 198 1023.096 . 168 132C729 113standard will be sufficien
35、tly similar in expansion and densitycharacteristics so that the same table can be used.7.2 Determination of Temperature Coeffcient of DensityMeasure the density of the solution at approximately 25 and45C using the Bingham pycnometer, Test Method D1217,orequivalent pycnometer method. Calculate the te
36、mperaturecoefficient of density, Cr, as follows:Cr5 rT12rT2!/T12 T2! (4)where:Cr= temperature coefficient of the solution,g/cm3C, andrT1and rT2= density of the solution at temperature T1and T2, g/cm3.7.3 Equations for Determination of Density:NOTE 2Alternative equations or method of calculation may
37、be used inconjunction with different density tables and standard settling tempera-tures.7.3.1 These equations relate the specimen density to itssettling temperatures. Express the exact relationship:rT5rs1 CrT 2 Ts! (5)where:rT= density of specimen at its settling temperature, T, andrs= density of st
38、andard at its settling temperature, Ts,approximately 35C.7.3.2 If the thermal expansions of a specimen and standardare similar, express their densities at 25C as follows:r255rs251 Cr1 3asrs!T 2 Ts! (6)where:r25= specimen density at 25C,rs25= standard density at 25C, andas= linear expansion of standa
39、rd expansion of speci-men.7.3.3 It is convenient to fix 35C as the settling temperatureof the standard, as it will vary slightly with heating rate,operator, and liquid density. The specimen settling temperaturemust be corrected as follows:Tc5 T 1 35 2 Ts! (7)where:Tc= corrected specimen settling tem
40、perature,T = observed specimen settling temperature, andTs= observed standard settling temperature.Eq 6 then becomes:r255rs251 Cr1 3asrs!Tc2 35! (8)7.4 Density TableThis table is prepared and used whenmany routine densities are to be determined. Eq 8 is solved forTcbetween 25 and 45C in 0.1C increme
41、nts, and specimendensity at 25C is tabulated with corrected specimen settlingtemperature Tc. A typical density table is shown in Table 2.7.5 Density Equation for Unlike ExpansionsIf the thermalexpansions of specimen and standard differ, specimen densitywill be in error by approximately 0.0001 g/cm3f
42、or every20 3 107/C mismatch in expansion. This error is greater ifthe specimen settles above 35C and less if it settles below35C. Use the following equation, which is accurate to60.0001 g/cm3:r255rs251.0000 2 30 as! 1 3aTc2 25!# 1 CrTc2 35! (9)where: a = linear expansion coefficient of specimen.8. P
43、rocedure for Determining Density of Test Specimens8.1 Prepare the specimen for testing by cutting from thesample a piece comparable in size with the standard. The testspecimen should be smooth and free of bubbles and cracks.Identify the specimen using a diamond-point marking pencil orby cutting it t
44、o a distinctive shape. Clean the specimen inreagent grade alcohol or acetone and wipe dry with silicone-free lens tissue. Place specimen in the solution (Note 3) thatcontains the standard. The bath and solution temperaturesshould be approximately 256 3C, and both specimen andstandard should float.NO
45、TE 3Adsorbed moisture on the specimen surface will lower themeasured density. Moisture, from condensation, on the solution surfaceshould be removed by periodically filtering the solution through coarsefilter paper.8.2 Place all the tubes, thermometers, stoppers, etc., in theirproper location in the
46、bath, and rapidly heat the bath (1 to2C/min), noting the temperature of the density solution atwhich the test specimen (or the standard) begins to settle.8.3 Adjust the bath temperature by cooling to 2 to 4Cbelow the expected settling temperature of the specimen (orstandard). Allow the bath and solu
47、tions to come to equilibriumfor 10 min, then heat the bath at a rate of 0.1 6 0.02C/min.Heating rates can be controlled by adjusting the power to thehotplate or immersion heater and the cooling water flow rate.Cooling water is used as a fine adjustment of heating rate.8.4 As either the specimen or s
48、tandard begin to settle in thesolutions, note the temperature at which either is halfwaybetween upper and lower cage disks. The bath and densitysolution temperatures must agree within 0.4C when thetemperature is recorded, with the bath temperature beinghigher. Record T and Ts.8.5 Calculate the corre
49、cted specimen settling temperature,Tc, by Eq 7. From an appropriate density table prepared fromEq 4 and Eq 8, read the density that corresponds to thecorrected specimen settling temperature, Tc. This density is thedensity of the specimen at 25C, r25.8.6 Up to three test specimens can be run in a single tubesimultaneously.C729 1149. Report9.1 Report the following:9.1.1 Identification of test sample, product, manufacturer,code number, date, etc. as required,9.1.2 Test information, including test date,
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