1、Designation: E324 16Standard Test Method forRelative Initial and Final Melting Points and the MeltingRange of Organic Chemicals1This standard is issued under the fixed designation E324; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, 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.1. Scope1.1 This test method
3、covers the determination, by a capil-lary tube method, of the initial melting point and the finalmelting point, which define the melting range, of samples oforganic chemicals whose melting points without decomposi-tion fall between 30 and 250C.1.2 This test method is applicable only to crystalline m
4、ate-rials that are sufficiently stable in storage to met the require-ments of a satisfactory standard sample as defined in Section 7.1.3 This test method is not directly applicable to opaquematerials or to noncrystalline materials such as waxes, fats, andfatty acids.1.4 Review the current Safety Dat
5、a Sheets (SDS) for de-tailed information concerning toxicity, first aid procedures,handling, and safety precautions.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafe
6、ty 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:2D852 Test Method for Solidificat
7、ion Point of BenzeneD1015 Test Method for Freezing Points of High-PurityHydrocarbonsD1016 Test Method for Purity of Hydrocarbons from Freez-ing PointsD1493 Test Method for Solidification Point of IndustrialOrganic Chemicals (Withdrawn 2004)3D1982 Test Method for Titer of Fatty AcidsD6809 Guide for Q
8、uality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsD6875 Test Method for Solidification Point of IndustrialOrganic Chemicals by ThermistorE1 Specification for ASTM Liquid-in-Glass ThermometersE11 Specification for Woven Wire Test Sieve Cloth and TestSieves
9、E180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals (Withdrawn 2009)3E1547 Terminology Relating to Industrial and SpecialtyChemicals3. Terminology3.1 Definitions:3.1.1 See Terminology E1547 for definition of terms used inthis tes
10、t method.3.1.2 initial melting point, nthe temperature at whichpositive evidence of liquefaction is observed (see 9.4.1).3.1.3 final melting point, nthe temperature at which thelast crystal disappears into the melt.4. Summary of Test Method4.1 1 This test method determines initial and final meltingp
11、oints by a relative procedure, utilizing a standard sample thathas been assigned jointly accepted melting point values by theconcerned parties (such as a supplier and a consumer, or NISTand a manufacturer). The absolute values of the initial and finalmelting points are not critical factors, as long
12、as the producerand consumer agree to use the standard sample and itsempirically assigned values as the basis for testing andspecifications agreements. Simultaneous readings are taken of1This practice is under the jurisdiction of ASTM Committee D16 on AromaticHydrocarbons and Related Chemicals and is
13、 the direct responsibility of Subcom-mittee D16.15 on Industrial and Specialty General Standards.Current edition approved Nov. 1, 2016. Published November 2016. Originallyapproved in 1967. Last previous edition approved in 1999 as E324 99 which waswithdrawn April 2001 and reinstated in November 2016
14、. DOI: 10.1520/E0324-16.2For 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 hi
15、storical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1these temperatures for an unknown and the agreed standardsample of the same chemical; the respective initial meltingpoints and the respecti
16、ve final melting points are recorded. Thedifferences in melting point values between the assigned andthe observed melting points for the standard are added alge-braically to the corresponding figures for the unknown, therebygiving the corrected values reported.5. Significance and Use5.1 It has long
17、been recognized that narrow melting rangeand high final melting point are good indications of high purityin crystalline organic compounds. Several ASTM test methodsuse these criteria to assay the purity of organic compounds(Note 1). Test Method D1016 uses the cryoscopic constantsplus the melting poi
18、nt of 100 % pure material to calculate themol percent purity of the sample under test.NOTE 1Other ASTM test methods using melting (or freezing point)data to indicate sample purity are Test Methods D852, D1015, D1016,D1493, D1982, and D6875.5.2 The relatively simple and rapid test prescribed in thist
19、est method shows the sample under test to be either more orless pure than the standard sample. For specification purposes,a minimum allowable purity can be assured by setting limits onthe differences in final melting points and the melting rangesbetween the standard sample and the sample under test.
20、6. Apparatus6.1 Capillary Melting Point Apparatus4consisting of asilicone fluid bath (Note 2), stirrer, immersion heater coil,transformer control, and adjustable magnifier constructed andoperated in such a way that the temperature around the samplesand thermometer is uniform, and can be easily contr
21、olledwithin the limits required by this test method. A means shall beprovided so that the capillary tubes can be introduced into thebath and properly positioned without removing the thermom-eter from the heating bath.NOTE 2The silicone fluid used in this study had a viscosity of about50 cSt (mm2/s)
22、at 25C and a flash point over 300C.6.2 Melting Point Capillary TubesThe capillary tube tocontain the sample shall be a glass tube approximately 90 to120 mm long and 0.9 to 1.1 mm in internal diameter with walls0.2 to 0.3 mm thick and closed at one end.6.3 Thermometer, of the partial immersion type a
23、nd ofsuitable range selected from Specification E1. It shall bedivided into subdivisions of 0.5C and capable of being read to0.1C.6.4 SieveThe 125-m sieve used in preparation of thestandard sample and of samples of material to be tested shallmeet the requirements of Specification E11.7. Standard Sam
24、ple7.1 The standard sample shall be homogeneous and of thesame basic chemical composition as the unknown to beanalyzed. This condition is satisfied when both materials arequite pure, or when both the standard and unknown have beenmade by the same industrial process. Significant deviationsfrom identi
25、ty in chemical composition lead to some loss ofprecision.7.2 The standard sample must be uniformly blended, andthe particle size must be fine enough so that a test specimen ofapproximately 0.1 g will yield reproducible melting point data.In preparing a standard sample from coarse crystalline materia
26、lthe sample should be ground fine, passed through a 125-msieve, and blended thoroughly before subdividing and storingfor use in this test.7.3 The standard sample shall be stored under such condi-tions that its quality will not deteriorate. This is vital to thesuccess of the method, since deteriorati
27、on of the standardsample, causing lowered initial and final melting temperatures,will result in falsely high indications of the purity of thematerials under test. Many chemicals are somewhathygroscopic, and it may be agreed that the standard or both thestandard and the sample are to be conditioned b
28、y appropriatemeans before the melting range is determined.7.4 In the case of two laboratories determining the meltingpoint or melting range of a material (as in the case of thelaboratories of a supplier and of a consumer), it is necessarythat the standard used by each be a portion of the same standa
29、rdsample with preassigned values of the initial and final meltingpoints.8. Sampling8.1 A bulk sample shall be withdrawn by means appropriateto the processing, shipment, or storage conditions. This bulksample shall be blended and subdivided, with grinding stepswhere appropriate, until a blended sampl
30、e of 1 to 10 g with aparticle size passing 125-m sieve is obtained.9. Procedure9.1 Grind approximately 0.1-g test specimens of the stan-dard sample and of the unknown sample as finely as possiblein mortars or on pieces of flat glass with spatulas. Charge themelting point capillary tubes with the fin
31、ely ground testspecimens to form packed columns in the bottom of the tubesfrom 3 to 4 mm in height. The capillary tubes are packedtightly by adding the powdered test specimen in three or fourincrements, and being sure that each increment is well packed.59.2 Preheat the oil bath to approximately 15C
32、below theexpected melting range. Then adjust the temperature rise rate to1 6 0.2C/min during the actual melting of the sample.9.3 Without removing the thermometer from the heatingbath, place the packed capillary tubes containing the standardand unknown sample in the heating bath when the temperature
33、is about 5C below the expected initial melting point. Hold thepacked capillary tubes adjacent to the thermometer bulb insuch a way that they and the thermometer bulb are at a uniformtemperature.4The interlaboratory study was made and the precision data obtained using aThomas-Hoover “Uni-Melt” appara
34、tus. Similar data may be obtained on othercapillary melting point apparatus suitably designed for this procedure and availablefrom other suppliers.5In the “Uni-Melt” apparatus, a vibrator suitable for packaging the tubes is partof the equipment; alternative ways of packing the tube firmly are permis
35、sible.E324 1629.4 Observe the samples closely through the magnifier andrecord the initial melting point and the final melting point toobtain the melting range.9.4.1 The initial melting point is defined as the temperatureat which positive evidence of liquefaction is observed. Justbefore this temperat
36、ure is reached, samples show varyingdegrees of shrinkage away from the walls of the capillary tube.Then, the main column of sample collapses against the side orthe bottom of the capillary, or both. After a further rise intemperature, which may vary from 0.2C to more than 1C, theportion of the sample
37、 in contact with the tube is observed toform a distinct liquid film which wets the surface. Theliquefaction or wetting may occur at the bottom, sides, front, orrear of the capillary tube. When wetting occurs at the back, thepoint may be missed unless care is taken to watch the rear ofthe tube. The c
38、apillary tube may be rotated to view the rearside. The area of the wetted surface should represent 25 to50 % of the area of the tube in contact with the sample andvisible to the operator. The temperature at this point is taken asthe initial melting point. The minute droplets resulting from thesmall
39、particles which adhere to the wall of the capillary tubeafter the shrinkage of the sample should not be considered inarriving at the initial melting point. Neither should a darkeningor change of color of the sample be considered, but suchchanges should be noted along with any additional evidence ofd
40、ecomposition.9.4.2 The final melting point is the temperature at which thelast sample crystal disappears into the melt.10. Calibration10.1 Calculate the corrected initial and final melting pointsin degrees Celsius as follows:Ai5 Bi1 Di2 Ci(1)Af5 Bf1Df2 Cf(2)where:Ai= corrected initial melting point
41、of unknown sample,Af= corrected final melting point of unknown sample,Bi= observed initial melting point of unknown sample,Bf= observed final melting point of unknown sample,Di= assigned initial melting point of standard sample,Df= assigned final melting point of standard sample,Ci= observed initial
42、 melting point of standard sample, andCf= observed final melting point of standard sample.11. Report11.1 Report as the melting range the initial melting pointand the final melting point to the nearest 0.1C.12. Precision and Bias12.1 Precision:12.1.1 The following criteria should be used for judging
43、theacceptability of results (see Note 3).12.1.2 Repeatability (Single Analyst)The standard devia-tion for a single melting point value has been estimated to be0.18C at 228 DF. The 95 % limit for the differences betweentwo such values is 0.5C.NOTE 3The above precision estimates are based on an interl
44、aboratorystudy in 1973 on five samples melting at approximately 75, 105, 150, 200,and 235C. One analyst in each of 13 laboratories performed duplicatedeterminations and repeated one day later, for a total of 260 determina-tions.6Practice E180 was used in developing these precision estimates.12.2 The
45、 use of a thermometric correction automaticallycompensates for variations in equipment and heatingtechniques, and very importantly, the variation between differ-ent analysts in the selection of melting stages as characteristicof the recorded initial and final temperatures.12.3 BiasSince there is no
46、accepted reference materialsuitable for determining the bias in this test method formeasuring melting point, bias has not been determined.13. Quality Guidelines13.1 Laboratories shall have a quality control system inplace.13.1.1 Confirm the performance of the test instrument ortest method by analyzi
47、ng a quality control sample followingthe guidelines of standard statistical quality control practices.13.1.2 A quality control sample is a stable material isolatedfrom the production process and representative of the samplebeing analyzed.13.1.3 When QA/QC protocols are already established inthe test
48、ing facility, these protocols are acceptable when theyconfirm the validity of test results.13.1.4 When there are no QA/QC protocols established inthe testing facility, use the guidelines described in GuideD6809 or similar statistical quality control practices.14. Keywords14.1 analysis; capillary tub
49、e; melting point; melting range6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:E15-1020. ContactASTM CustomerService at serviceastm.org.E324 163ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This stan
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