Near the southern tip of Greenland lies the ancient mining town ivittuut. Ivittuut was once the source of the world's largest cryolite, an extremely rare mineral that was used to extract metal aluminum from bauxite in history. Although cryolite mines have been found elsewhere on earth, ivetut is a place where cryolite is allowed to be mined commercially. Now it is full of dilapidated houses and old mining machinery.
Cryolite was discovered by British miners in ivetut in 1799. At first, they were engaged in silver mining around the town, but they found that the metal silver content in the vein was too low to make the business profitable, so they stopped mining. But 60 years later, Danish engineers began to try to mine cryolite here to obtain its metal aluminum.
Cryolite, also known as sodium hexafluoroaluminate, is a colorless compound containing sodium, fluorine and aluminum. The name comes from a Greek word κρνο (Cryos), which means "ice", and λιθο (LITHOS) means "stone".
The aluminum content in cryolite is only 13%, compared with 50% in bauxite. Therefore, bauxite is often regarded as the main source of extracting metal aluminum in the world, and bauxite is also relatively common, but the problem is that the chemical process of extracting metal aluminum from bauxite has proved to be very difficult. The method usually used by people is to pass the current through the molten ore, which is a technology called electrolysis. However, it is found that the melting temperature of bauxite is very high, more than 2000 ° C. If you want to obtain such a high temperature, you must pay a high cost. Therefore, the method of extracting metal aluminum by electrolytic bauxite has not been popularized.
In 1886, the American chemist Charles Martin hall and the Frenchman Paul h é roult found that if a small amount of cryolite was added to the bauxite solution, the melting point of bauxite would be reduced below 1000 ℃. In addition to reducing the melting point, cryolite also helps to better dissolve alumina, improve the conductivity of the solution, and support electrolysis at higher voltage. This is the hall – h é roult process.
Since the discovery of the hall hurut process, aluminum has changed from a precious metal to a cheap commodity in people's eyes. The falling price of aluminum makes it appear in people's daily life in the form of jewelry, utensils, spectacle frames, optical instruments and tableware. The hard alloy formed after the synthesis of aluminum and other metals has become the main raw material of aircraft manufacturing industry.
During World War II, the Allies sent a platoon to yvitut to protect it from the Nazis, because the cryolite here played an important role in the production of aircraft. In order to strengthen its control, the U.S. Coast Guard has established a U.S. military base opposite the fjord of ivetut, which can accommodate hundreds of soldiers. For the protection of ivetut, it was not allowed to take photos or write to family or friends during the war, for fear that the Nazis would intercept the information.
After the war, Denmark continued to mine cryolite until the mines here dried up. Ivetut was closed in 1987. Today, cryolite is replaced by synthetic sodium aluminum fluoride in the hall hrut process, which has been used to this day.
