Charles Martin Hall was an American scientist best-known for inventing a process that could produce aluminium cheaply. Hall produced the first samples of aluminium in 1886 and the process involved passing an electric current through alumina dissolved in cryolite. Around the same time, French scientist Paul Heroult produced aluminium using the same process and therefore, this process of making aluminium is known as the Hall-Heroult process. The Hall-Heroult process reduced the price of aluminium drastically and made it more affordable.
Hall and Alfred E. Hunt formed the Reduction Company of Pittsburgh, which opened the first large-scale aluminum production plants. The Reduction Company later became the Aluminum Company of America (ALCOA). Hall won the Perkin Medal, the highest award in American industrial chemistry, in 1911.
Sir Humphry Davy was born in 1778 in Penzance in Cornwall. He is known for his work in electrochemistry, discovery of the existence of aluminium and invention of a miner’s safety lamp. He prepared nitrous oxide, which is commonly known as the laughing gas, and was subsequently hired as an assistant lecturer in chemistry at the Royal Institution. He became a fellow of the Royal Society in 1803 and was awarded its Copley Medal in 1805.
Freidrich Wohler was a German chemist, who is famous for his synthesis of urea and isolation of many chemical elements. He co-discovered beryllium, silicon and silicon nitride and systhesized calcium carbide. In 1827, Wohler extracted aluminium as a powder by reacting potassium with anhydrous aluminium chloride. In 1845, he established the lightness of aluminium.
Henri Saint-Claire Deville was a French chemist. He discovered anhydrous nitric acid (nitrogen pentoxide) in 1849 and he succeeded in obtaining metallic aluminium in 1855 and displayed a solid bar of aluminium at a Paris exhibition in the same year. He devised a method by which the metal could be prepared on a large scale by the aid of sodium, the manufacturing process of which was developed by him. 
Karl Josef Bayer was an Austrian chemist, known for his invention of the Bayer process, by which alumina is extracted from bauxite. In 1887, Bayer discovered that aluminium hydroxide precipitated from an alkaline solution was crystalline and could be filtered and washed more easily than that precipitated from an acid medium by neutralization. In 1889, Bayer developed and patented the Bayer process of extracting alumina from bauxite. The Bayer process helped in reducing the price of aluminium significantly.
Paul Heroult was a French scientist best known for the discovery of the Hall-Heroult electrolysis process for making aluminium. He made this invention in 1886, the same year in which American scientist Charles Martin Hall invested the same process for making aluminium. The process is therefore known as the Hall-Heroult process.
