1. Melting point concept
Melting point is the physical property of a substance. In physical principle, melting point is the temperature at which a solid changes its state from solid state (melting) to liquid state, usually denoted by Tm. In most cases the melting point of an object is the freezing point. There are two factors that have a big impact on the melting point. One is the pressure. The melting point of a substance is usually at one atmosphere. The second is the impurity of the material. The melting point of impurity will drop. The melting point of rubber additives is used to determine the purity of products.
2. Classification of melting point detection
Melting point according to melting degree can be divided into: initial melting point, middle melting point, final melting point. Initial melting point: the temperature when the sample in the capillary tube is just liquefied; Final melting point: temperature when the sample is completely liquefied in the capillary tube; Middle melting point: between the initial melting and the final melting, generally refers to the temperature when the sample in the capillary is melted into a transparent shape and can be visually measured to penetrate the capillary.
2.1 Melting point detection is divided into capillary method and non-capillary method according to the principle of instruments.
Melting point detection can be divided into manual, semi-automatic and automatic melting point detection according to the degree of automation.