July 24, 2024

Determination of Melting point of organic compounds

Determination of Melting point of organic compounds


To determine the Melting point of a given solid sample.



Thiel’s tube, Thermometer, Thread/Rubberring, Capillary tube • Chemicals: Liquid paraffin (Note: If liquid paraffin is not available, melting point be determined by using concentrated sulphuric acid with caution.)


 The Melting Point of the compound is the temperature at which the solid phase change to the liquid base. The high purity of the organic compound is indicated by a sharp melting point. Laboratory experiments for the determination of melting point will put light on the purity concept.


1. Take a capillary and seal it at one end, by holding it in flame for a while.

2. Take a small quantity (about 3-5mg) of the powdered organic compound into sealed

3. Tie the capillary tube containing the given sample of the organic compound to the thermometer near its bulb with the help of thread / rubberring.

4. Immerse the thermometer with a capillary tube into liquid paraffin taken in a Thiel’s tube. Care should be taken not to allow thread/rubber rings to come in contact with liquid paraffin.

5. Heat the Thiel’s tube slowly with the help of a gas burner.

6. The rate of heating should not be more than 3°C/min.

7. Note the temperature at which solid organic compound is converted to liquid and record it as the melting point of the given sample of an organic compound.

8. Repeat the procedure twice and take the observation.

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