Melting Points and the Melting Range of Organic Chemicals ASTM E324

The relative initial and final melting points and melting range of organic chemicals is determined by the standard method ASTM E324. It has been recognized that the narrow melting range and high final melting point are good indications of high purity in crystalline organic compounds.

Scope:

ASTM E324 is used to determine the melting point which is a simple and fast method used in many diverse areas of chemistry to get a first impression of the purity of a substance. This is because even small quantities of impurities change the melting point, or at least clearly enlarge its melting range. 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.

Test Procedure:

The ASTM E324 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. The accuracy of a melting point record is assured by: (a) careful sample preparation, (b) proper instrument setup, and (c) routine calibration of the instrument’s temperature scale against certified melting point standards.

Sample size:

Crystalline organic compounds are collected in order to measure final melting points and melting range ASTM E324.

Data:

he Data stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

Field of Application:

The test is an important technique for gauging purity of organic and pharmaceutical compounds. The MP determination is a fast and cost effective technique which remains a strong link to the vast pre-instrumental chemistry literature.