A melting-point apparatus is a scientific instrument used to determine the melting point of a substance. Some types of melting-point apparatuses include the Thiele tube , Fisher-Johns apparatus, Gallenkamp (Electronic) melting-point apparatus and automatic melting-point apparatus
While the outward designs of apparatuses can vary greatly, most apparatuses use a sample loaded into a sealed capillary ( melting-point capillary ), which is then placed in the apparatus. The sample is then heated, either by a heating block or an oil bath, and as the temperature increases, the sample is observed to determine when the phase change from solid to liquid occurs. The operator of the apparatus records the temperature range starting with the initial phase-change temperature and ending with the completed phase-change temperature. The temperature range that is determined can then be averaged to gain the melting point of the sample being examined.
Apparatuses usually have a control panel that allows the starting and final temperatures, as well as the temperature gradient (in units 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 that allow the start and end of the melting point range to be recorded.