A MEL-TEMP 3.0 melting point instrument. Samples in capillaries are inserted from the top; the eyepiece has a magnifier; the temperature can be adjusted from the digital panel at the bottom.

A melting point apparatus is a scientific instrument used to determine the melting point of a substance. Four types of melting point apparatuses are the Thiele tube, Fisher-Johns apparatus, Gallenkamp (Electronic) melting point apparatus and the automatic melting point apparatus. Some specific models of these include the Büchi B-540, the MEL-TEMP 3.0, and the Fisher-Johns apparatus.

Designs vary; generally, a sample is loaded into a sealed capillary (melting point capillary). It is placed in the machine.

The sample may be heated electrically, either via a heating block, or an oil bath. There usually is a control panel which allows the starting and final temperatures, as well as the temperature gradient (in °C per minute) to be programmed.

Some machines have several channels which permit more than one sample to be tested at a time. The control panel might have buttons which allow the start and end of the melting point range to be recorded.

Thiele tube

A Thiele tube may also be used to determine melting and boiling points. It uses a manually-heated recirculating oil bath to heat the sample, which may be more difficult to control.