February 22, 2024

Determination of Boiling point of organic compounds

Determination of Boiling point of organic compounds


To determine Boiling point of given liquid sample



Thiel’s tube, Thermometer,Thread/Rubberring, capillary tube


Liquid paraffin (Note: If liquid paraffin is not available, melting point can be determined by using concentrated sulphuric acid with caution.)


Boiling point of liquid is that temperature at which vapour pressure of liquid equals to atmospheric pressure Boiling point is employed as criterion for identity and purity of liquid organic substance.


1. Fill the Thiel’s tube with liquid paraffin to more than 50% capacity of main limb and clamp it.

2. Seal one end of capillary so that there is no opening left.

3. Place about 3-4 drops of liquid in the boiler tube filling it to a height of 8-10 mm

4. Insert the capillary, open end down in liquid containing in the boiler tube.

5. Attach the boiler tube to thermometer bulb with the help of thread and suspend it in Thiel’s tube.

6. Heat the Thiel’s tube gradually with low flame.

7. When bubbling from capillary initiates, discontinue heating. There will be steady stream of bubbles from capillary tube.

8. When bubbles tops emerging and liquid begins to rush in capillary tube, note the temperature. This is of liquid.

9. Repeat the procedure twice and take observations.

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