ASTM E324-23

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E324 − 16 E324 − 23
Standard Test Method for
Relative Initial and Final Melting Points and the Melting
Range of Organic Chemicals
This standard is issued under the fixed designation E324; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript 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. Scope Scope*
1.1 This test method covers the determination, by a capillary tube method, of the initial melting point and the final melting point,
which define the melting range, of samples of organic chemicals whose melting points without decomposition fall between 30 and
250°C.30 °C and 250 °C.
1.2 This test method is applicable only to crystalline materials that are sufficiently stable in storage to met the requirements of a
satisfactory standard sample as defined in Section 77.
1.3 This test method is not directly applicable to opaque materials or to noncrystalline materials such as waxes, fats, and fatty
acids.
1.4 Review the current Safety Data Sheets (SDS) for detailed information concerning toxicity, first aid procedures, handling, and
safety precautions.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D852 Test Method for Solidification Point of Benzene
D1015 Test Method for Freezing Points of High-Purity Hydrocarbons (Withdrawn 2019)
D1016 Test Method for Purity of Hydrocarbons from Freezing Points (Withdrawn 2019)
This practice test method is under the jurisdiction of ASTM Committee D16 on Aromatic, Industrial, Specialty and Related Chemicals and is the direct responsibility
of Subcommittee D16.04 on Instrumental Analysis.
Current edition approved Nov. 1, 2016April 1, 2023. Published November 2016April 2023. Originally approved in 1967. Last previous edition approved in 19992016 as
E324 – 99 which was withdrawn April 2001 and reinstated in November 2016. DOI: 10.1520/E0324-16.16. DOI: 10.1520/E0324-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E324 − 23
D1493 Test Method for Solidification Point of Industrial Organic Chemicals (Withdrawn 2004)
D1982 Test Method for Titer of Fatty Acids
D6809 Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related Materials
D6875 Test Method for Solidification Point of Industrial Organic Chemicals by Thermistor
E1 Specification for ASTM Liquid-in-Glass Thermometers
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
E180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals
(Withdrawn 2009)
E1547 Terminology Relating to Industrial and Specialty Chemicals
3. Terminology
3.1 Definitions:
3.1.1 See Terminology E1547 for definition of terms used in this test method.
3.1.2 initial melting point, n—the temperature at which positive evidence of liquefaction is observed (see 9.4.1).
3.1.3 final melting point, n—the temperature at which the last crystal disappears into the melt.
4. Summary of Test Method
4.1 1 This test method determines initial and final melting points by a relative procedure, utilizing a standard sample that has been
assigned jointly accepted melting point values by the concerned parties (such as a supplier and a consumer, or NIST and a
manufacturer). The absolute values of the initial and final melting points are not critical factors, as long as the producer and
consumer agree to use the standard sample and its empirically assigned values as the basis for testing and specifications
agreements. Simultaneous readings are taken of these temperatures for an unknown and the agreed standard sample of the same
chemical; the respective initial melting points and the respective final melting points are recorded. The differences in melting point
values between the assigned and the observed melting points for the standard are added algebraically to the corresponding figures
for the unknown, thereby giving the corrected values reported.
5. Significance and Use
5.1 It has long been recognized that narrow melting range and high final melting point are good indications of high purity in
crystalline organic compounds. Several ASTM test methods use these criteria to assay the purity of organic compounds (Note 1).
Test Method D1016 uses the cryoscopic constants plus the melting point of 100 % pure material to calculate the mol percent purity
of the sample under test.
NOTE 1—Other 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 this test method shows the sample under test to be either more or less pure
than the standard sample. For specification purposes, a minimum allowable purity can be assured by setting limits on the
differences in final melting points and the melting ranges between the standard sample and the sample under test.
6. Apparatus
6.1 Capillary Melting Point Apparatus consisting of a silicone fluid bath (Note 2), stirrer, immersion heater coil, transformer
control, and adjustable magnifier constructed and operated in such a way that the temperature around the samples and thermometer
is uniform, and can be easily controlled within the limits required by this test method. A means shall be provided so that the
capillary tubes can be introduced into the bath and properly positioned without removing the thermometer from the heating bath.
NOTE 2—The silicone fluid used in this study had a viscosity of about 50 cSt (mm2/s) at 25°C25 °C and a flash point over 300°C.300 °C.
The interlaboratory study was made and the precision data obtained using a Thomas-Hoover “Uni-Melt” apparatus. Similar data may be obtained on other capillary
melting point apparatus suitably designed for this procedure and available from other suppliers.
E324 − 23
6.2 Melting Point Capillary Tubes—The capillary tube to contain the sample shall be a glass tube approximately 9090 mm to 120
mm long and 0.9 to 1.1 mm 0.9 mm to 1.1 mm in internal diameter with walls 0.2 to 0.3 mm 0.2 mm to 0.3 mm thick and closed
at one end.
6.3 Thermometer, of the partial immersion type and of suitable range selected from Specification E1. It shall be divided into
subdivisions of 0.5°C0.5 °C and capable of being read to 0.1°C.0.1 °C.
6.4 Sieve—The 125-μm125 μm sieve used in preparation of the standard sample and of samples of material to be tested shall meet
the requirements of Specification E11.
7. Standard Sample
7.1 The standard sample shall be homogeneous and of the same basic chemical composition as the unknown to be analyzed. This
condition is satisfied when both materials are quite pure, or when both the standard and unknown have been made by the same
industrial process. Significant deviations from identity in chemical composition lead to some loss of precision.
7.2 The standard sample must be uniformly blended, and the particle size must be fine enough so that a test specimen of
approximately 0.1 g will yield reproducible melting point data. In preparing a standard sample from coarse crystalline material the
sample should be ground fine, passed through a 125-μm125 μm sieve, and blended thoroughly before subdividing and storing for
use in this test.
7.3 The standard sample shall be stored under such conditions that its quality will not deteriorate. This is vital to the success of
the method, since deterioration of the standa
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