Humphry Davy

Who Prised New Metals Out of Salt · Chemist · 1778–1829

The apothecary's apprentice turned celebrity lecturer who built the largest battery in the world, used electricity to prise six new elements out of compounds nothing else could break, and refused to patent the lamp that saved miners' lives.

Who was Davy?

Humphry Davy was born in Penzance in 1778, apprenticed to a surgeon-apothecary and essentially self-taught. He made his name at the Pneumatic Institution in Bristol by breathing nitrous oxide and publishing an account of its effects on himself — reckless, famous, and very nearly fatal on more than one occasion. Appointed to the Royal Institution in London, he became the most celebrated lecturer of his age, filling the theatre until Albemarle Street had to be made one-way to handle the carriages. He also built the most powerful voltaic battery then in existence and used it as a chemical crowbar. In 1807 he passed a current through molten potash and watched bright globules of an unknown metal appear and catch fire on contact with water: potassium, an element locked inside a compound no chemical reagent could open. Sodium followed within days, then calcium, magnesium, strontium and barium. He demonstrated that chlorine is an element, overturning Lavoisier's insistence that every acid contains oxygen. He invented the miners' safety lamp and refused to patent it, saying his only object was to serve humanity. In 1813 he took on a bookbinder's apprentice named Michael Faraday as a laboratory assistant — often called his greatest discovery, a remark Davy did not enjoy, and he later opposed Faraday's election to the Royal Society.

Major achievements

• Isolated potassium and sodium in 1807 by electrolysis of their molten compounds
• Went on to isolate calcium, magnesium, strontium and barium
• Proved chlorine is an element, disproving Lavoisier's theory of acids
• Invented the miners' safety lamp and refused to patent it
• Built the most powerful voltaic battery then in existence

Life in brief

• 1778 — Born in Penzance: Apprenticed to a surgeon-apothecary; largely self-taught.
• 1799 — Nitrous oxide: Breathes it himself at the Pneumatic Institution and publishes the effects.
• 1801 — The Royal Institution: Becomes the most celebrated lecturer in London.
• 1807 — Potassium and sodium: Prised out of molten compounds by the largest battery in the world.
• 1808 — Four more elements: Calcium, magnesium, strontium and barium.
• 1810 — Chlorine is an element: Overturning Lavoisier's theory that acids must contain oxygen.
• 1815 — The safety lamp: Invented and deliberately left unpatented.
• 1813 — Engages Faraday: A bookbinder's apprentice, taken on as laboratory assistant.

Explore the life of Davy — five chapters

1. Breathing the Gas Himself — Penzance to Bristol, and a very dangerous self-experiment
2. Albemarle Street Made One-Way — The most popular lecturer in England
3. Six Elements in Two Years — Electricity as a chemical crowbar
4. The Lamp He Would Not Patent — And what happened after it went into the pits
5. Faraday — The bookbinder's apprentice, and the vote against him

Read the five-chapter life of Humphry Davy →

Where Davy appears in your course

Humphry Davy has a genuine claim on 25 lessons of the Pearson Edexcel International GCSE science course built into Incandio. Six of them:

• Ionic Bonding — Chemistry: This page claims that ionic compounds are made of charged particles, and the first serious evidence for it is Davy's. In 1807 he passed a current through molten potash — a compound no chemical reagent could decompose — and bright globules of an unknown metal appeared at one electrode and burned on contact with water. Potassium, then sodium days later, then four more elements. The significance is that the compound came apart at the ELECTRODES, with the metal appearing at one and not the other, which only makes sense if the compound already contains oppositely charged parts that a current can pull in opposite directions.
• Ionic Structures and Their Properties — Chemistry: Statement 1.43 is the principle Davy exploited in 1807 without being able to explain it. He could get nothing out of solid potash, so he melted it, and only then did the current pass and a metal appear at one electrode. That distinction — inert as a solid, decomposed as a liquid — is exactly this page's content, discovered as a practical obstacle rather than derived from theory. He is the right person to ask what it looked like from the inside, and how far you can get by exploiting a rule you do not yet understand.
• Giant Covalent Structures — Chemistry: That diamond and graphite are the same element is stated flatly on this page and was once an extraordinary claim, and Davy is among those who settled it experimentally. Using a large burning lens to focus sunlight, he burned a diamond in oxygen and showed that the only product was carbon dioxide — the same product as burning charcoal, and in the same proportion. There is no more direct way to demonstrate that the hardest substance known and the black stuff in a grate are one element. He is also the right person for graphite's use as an electrode, since his own electrolysis work depended on carbon that conducts.
• Metallic Bonding — Chemistry: Potassium and sodium had never been seen by anyone before Davy produced them in 1807, and his description is the best evidence there is that these properties come from structure rather than from anything mystical about metals. They were bright and shiny like other metals and conducted like other metals, and yet they were soft enough to cut with a knife and light enough to float on water — because group 1 atoms release only one electron each, giving a weak attraction. He is the right person to ask what it is like to be the first person to look at an element, and how you know it is a metal at all.
• Electrolysis — Chemistry: Davy is the first person to have performed the reaction on this page to any real purpose, and he did it without any of the vocabulary or theory it now comes with. He had no ions, no electrons, no half-equations — only a conviction that electricity was the force holding compounds together, and the largest battery in the world with which to test it. Six elements came out of that conviction in about eighteen months. He is worth asking about the gap between doing something and understanding it, particularly since the person who closed that gap was his own assistant.
• Group 1 — the Alkali Metals — Chemistry: Nobody had ever seen potassium or sodium before Davy produced them in 1807, and his account of what they did is the origin of everything on this page. He passed a current through molten potash and bright globules appeared which immediately caught fire on the moisture of the surface. He recorded that he danced about the room in ecstatic delight. What makes him the right figure here is that his description also contains the puzzle: these things were unmistakably metals — bright, shiny, conducting — and yet soft enough to cut and light enough to float, which no metal was supposed to be.

Begin

• Start a conversation with Davy — a dramatised, historically grounded AI portrayal
• Read the Historical Brief
• Explore the life of Davy — five chapters
• Find your exam topics · Meet all 208 figures