Big Ideas

IN CONTEXT

BRANCH

Chemistry

BEFORE

1735 Swedish chemist Georges Brandt discovers cobalt, the first of many new metallic elements to be found over the next 100 years.

1772 Italian physician Luigi Galvani notices the effect of electricity on a frog and believes electricity is biological.

1799 Alessandro Volta shows that touching metals produce electricity, and creates the first battery.

AFTER

1834 Davy’s former assistant Michael Faraday publishes the laws of electrolysis.

1869 Dmitri Mendeleev arranges the known elements into a periodic table, creating a group for the soft alkali metals that Davy had been the first to identify in 1807.

In 1800, Alessandro Volta invented the “voltaic pile” – the world’s first battery, and soon many other scientists began to experiment with batteries.

English chemist Humphry Davy realized that the battery’s electricity is produced by a chemical reaction. Electric charge flows as the pile’s two different metals (the electrodes) react via the brine-soaked paper between them. In 1807, Davy found that he could use the electric charge from a pile to split chemical compounds, discovering new elements, and pioneering a process that was later called electrolysis.

New metals

Davy inserted two electrodes into dry potassium hydroxide (potash), which he moistened by exposing it to the damp air in his laboratory so that it would conduct electricity. To his delight, metallic globules began to form on the negatively charged electrode. The globules were a new element: the metal potassium. A few weeks later, he electrolysed sodium hydroxide (caustic soda) in the same way and produced the metal sodium. In 1808, he used electrolysis to discover four more metallic elements – calcium, barium, strontium, and magnesium – and the metalloid boron. Like electrolysis, their commercial use would prove highly valuable.

Davy used apparatus similar to this in his lectures at London’s Royal Institution to show how electrolysis splits water into its two elements, hydrogen and oxygen.