ASTM_C_729_-_11_2016.pdf

Designation:C72911(Reapproved 2016)Standard 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 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 determine 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 determine 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 Density of Ceramics forElectron Device and Semiconductor Application(With-drawn 2001)33.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 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 comparator 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 the 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 obtained.3.2 Range of a Given Density SolutionA given densitysolution can be used to measure specimens whose density iswithin 60.0200 g/cm3of the density of the solution at 35C,byoperating the comparator bath in the range 25 to 45C.4.Significance and Use4.1 The sink-float comparator method of test for 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 research 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 the liquid and theprecision of the test may be reduced somewhat,however,athigher densities.5.Apparatus5.1 Single Tube and Multiple-Tube Comparators(TestMethod E77)A single-tube comparator can be constructedfrom materials readily available in a typical laboratory,anduseful if one wishes to measure the density of materials withina fairly narrow range,or if only a few tests need to be run eachday.The multiple-tube comparator can be purchased commer-cially.It is useful if materials with a wide range of density mustbe tested or if many specimens must be tested each day.Thecomparators shall consist 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,a1This test method is under the jurisdiction of ASTM Committee C14 on Glassand Glass Products and is the direct responsibility of Subcommittee C14.04 onPhysical and Mechanical Properties.Current edition approved Oct.1,2016.Published October 2016.Originallyapproved in 1972.Last previous edition approved in 2011 as C729 11.DOI:10.1520/C0729-11R16.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 cooling water coil made from copper tubing,an electricallydriven stirrer,and containing an immersion heater with rheostatfor controlling heating rate,or heated by an extern