Tube for Determining the Melting Point of a Substance

The Thiele tube is a glass utensil designed to contain and heat an oil bath. It has the shape of a tube with a triangular lateral handle through which the liquid will flow in a closed circuit.

It is used to determine the melting and boiling temperature of a solid substance ground into a fine powder. A mortar can be used to grind the sample.

The powdered sample is placed in a capillary tube that must be closed on one side.

Thiele tube is held in an upright position by means of a base and laboratory forceps. Oil is poured into the tube.

The capillary tube with the sample and with the open end upwards is immersed in the oil. Then a thermometer is placed and immersed in the oil, held by a rubber stopper at the top of the Thiele tube. And a small flame will be placed directly on the "side handle" which, when heated, will generate convection or circular flow maintaining an almost uniform temperature in the oil.

A small flame is then placed directly on the "side handle" which, when heated, will generate convection or a circular current maintaining an almost uniform temperature in the oil bath.

When the sample is observed to melt, the temperature at which the oil has reached will be its melting temperature.