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Research on the history of manganese dioxide

wallpapers News 2021-08-05
Early research on manganese dioxide
The cave paintings of Chauvet and Gargas in France use a series of mineral pigments. Dark brown and black are usually provided by manganese dioxide and charcoal. It is believed that this kind of pigment, which is quite elastic on the skin, could even be used for body painting earlier. Such long-term use shows that powder MnO2 (called "braunstein" in German) has a natural origin. It exists in the mineral pyrolusite. Despite its shiny metallic appearance, it is relatively easy to decompose.
Due to the long history of this substance, it is difficult to provide a "discoverer". Although pyrolusite is the main source of manganese, when the Swedish chemist Johan Gahn first produced the element in the 1770s, he actually determined the nature of the oxide. Another term for manganese dioxide in the form of pyrolusite also gave this element its name. The early source was magnesia in Greece. This ore was originally called magnesium, and then the magnesia was eventually corroded into manganese.
The development of manganese dioxide batteries
In a traditional zinc-carbon battery (more precisely, a battery, because the battery should consist of a series of repeated components), the positive electrode is a carbon rod passing through the center of the structure, with a metal cap on the outside. The negative electrode is the zinc casing of the battery, usually with a paper layer impregnated with ammonium chloride paste to separate it from most of the contents, which is a mixture of powdered carbon and manganese dioxide.
When the battery is working, manganese dioxide absorbs electrons and converts them into trimanganese trioxide (Mn2O3). There are alternative reactions in some variants of batteries, where zinc chloride is used instead of ammonium chloride, but both involve redox reactions. For many years, such zinc-carbon dry batteries have been the absolute backbone of the battery business, but now they only account for about 20% of the market, most of which are occupied by rechargeable batteries and more durable alkaline batteries.


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