Cryolite is also known as sodium hexafluoroaluminate or sodium aluminum fluoride. Its molecular formula is Na3AlF6. It is a small white crystal with no smell. Its solubility is greater than that of natural cryolite. Its specific gravity is 3, hardness is 2 ~ 3, melting point is 1009 ℃, and it is easy to absorb water and moisture. Cryolite is mainly used as flux for aluminum electrolysis, wear-resistant filler for rubber and grinding wheel, enamel opal, glass shading agent and metal flux, pesticide for crops, etc. Hall heroult process uses cryolite based fluoride melt as solvent to produce metal aluminum. So far, no other compound has been found to replace cryolite. This is because cryolite not only can dissolve alumina, but also has some other indispensable properties, such as no elements with higher electrical properties than aluminum, good stability, no decomposition, volatilization and deliquescence under general conditions, higher melting point than aluminum, good conductivity, saving electricity, etc. It can be said that without cryolite, there might not be such a large-scale aluminum industry in the world, the price would not be so low and the application would not be so extensive. The west coast of Greenland is the main producing area of cryolite, which was mined in 1987. At present, fluorite is mostly used to synthesize sodium fluoroaluminate 'target'_ Blank '> sodium hexafluoroaluminate is for industrial use. Spain, Russia and the United States also produced.

Cryolite is a flux in the aluminum industry. Alumina will dissolve in cryolite like a solution. Just as salt dissolves in water, cryolite is the solvent and alumina is the solute The electrolysis of alumina is not "melting electrolysis" in the real sense. In fact, what melts is cryolite. Alumina is only a dispersion, which is dispersed in liquid cryolite. The anions in the melt are complex atomic groups, not simple oxygen ions Using cryolite as solvent, alumina is dissolved and then electrolyzed Cryolite plays a key role here. It solves the difficulties of alumina with high melting point (up to 2050 ℃), non-conductive and unable to be electrolyzed alone After alumina is dissolved in cryolite, it can be electrolyzed at a temperature of 940980 ℃ Dissolution is much easier than melting, and the natural melting point is reduced. It can be said that without cryolite, there might not be such a large-scale aluminum industry in the world, the price would not be so low and the application would not be so extensive. 2、 The reasons why cryolite must be used for electrolytic aluminum are as follows: 1. Cryolite does not contain elements that are more electric than aluminum, has good stability, does not decompose, volatilize and deliquescence under general conditions, has a melting point higher than aluminum, has good conductivity, saves electricity, etc. 2. At the electrolysis temperature, the density of cryolite alumina molten liquid is 10% less than that of aluminum liquid, so the electrolytic aluminum liquid can be deposited on the cathode under the electrolyte, which can reduce the oxidation loss of aluminum and greatly simplify the structure of aluminum electrolytic cell; 3. It can better dissolve alumina, and the formed melt can be electrolyzed below the melting point of pure cryolite; And good liquidity.