According to the definition of physical chemistry, the melting point of a substance is the temperature at which the substance changes from a solid to a liquid. In the field of organic chemistry, melting point determination is a basic means to identify the nature of substances, and it is also one of the important methods for purity determination. Therefore, melting point tester occupies an important position in chemical and pharmaceutical research, and is an essential instrument for the production of medicine, spices, dyes and other organic crystalline substances.

The initial melting point refers to the temperature when the substance just begins to melt (at this time, it can be seen that the solid substance begins to collapse and has a wet phenomenon), which is called the initial melting point. The final melting point is the temperature at which the substance is completely melted (at this time, it can be seen that the substance is completely transformed into a transparent liquid ), which is called full melting. In general, the melting of a substance refers to the process from initial melting to full melting. The higher the purity of the substance, the narrower the temperature range of this process.

According to the pharmacopoeia method, when using pharmaceutical melting point tester to measure the melting point of active pharmaceutical ingredients, the drying degree of the sample, the filling height of the sample in the capillary tube, whether the sample is sufficiently crushed, and the filling compactness of the sample in the capillary tube will affect the melting point test results.