Zinc–carbon battery in the context of "Exposition Universelle (1900)"

Manganese dioxide is the inorganic compound with the formula MnO
₂. This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for MnO
₂ is for dry-cell batteries, such as the alkaline battery and the zinc–carbon battery, although it is also used for other battery chemistries such as aqueous zinc-ion batteries. MnO
₂ is also used as a pigment and as a precursor to other manganese compounds, such as potassium permanganate (KMnO₄). It is used as a reagent in organic synthesis, for example, for the oxidation of allylic alcohols. MnO
₂ has an α-polymorph that can incorporate a variety of atoms (as well as water molecules) in the "tunnels" or "channels" between the manganese oxide octahedra. There is considerable interest in α-MnO
₂ as a possible cathode for lithium-ion batteries.

The Exposition Universelle of 1900 (French pronunciation: [ɛkspozisjɔ̃ ynivɛʁsɛl]), better known in English as the 1900 Paris Exposition, was a world's fair held in Paris, France, from 14 April to 12 November 1900, to celebrate the achievements of the past century and to accelerate development into the next. It was the sixth of ten major expositions held in the city between 1855 and 1937. It was held at the esplanade of Les Invalides, the Champ de Mars, the Trocadéro and at the banks of the Seine between them, with an additional section in the Bois de Vincennes, and it was visited by more than fifty million people. Many international congresses and other events were held within the framework of the exposition, including the 1900 Summer Olympics.

Many technological innovations were displayed at the fair, including the Grande Roue de Paris ferris wheel, the Rue de l'Avenir moving sidewalk, the first ever regular passenger trolleybus line, escalators, diesel engines, electric cars, dry cell batteries, electric fire engines, talking films, the telegraphone (the first magnetic audio recorder), the galalith and the matryoshka dolls. It also brought international attention to the Art Nouveau style. Additionally, it showcased France as a major colonial power through numerous pavilions built on the hill of the Trocadéro Palace.

An alkaline battery (IEC code: L) is a type of primary battery where the electrolyte (most commonly potassium hydroxide) has a pH value above 7. Typically, these batteries derive energy from the reaction between zinc metal and manganese dioxide.

Compared with zinc–carbon batteries, alkaline batteries have a higher energy density and longer shelf life yet provide the same voltage.

Carl Gassner was a German physician (17 November 1855 in Mainz – 31 January 1942), scientist and inventor, better known to have contributed to improve the Leclanché cell and to have fostered the development of the first dry cell, also known as the zinc–carbon battery, less likely to break or leak and that could be effectively industrially produced at large scale.