Dec 172016


Today is the birthday (1778) of Sir Humphry Davy, 1st Baronet PRS MRIA FGS, a Cornish chemist and inventor whom I remember chiefly as the inventor of the Davy safety lamp for miners, but who had an illustrious career as a chemist.  He isolated a series of elements for the first time – potassium, sodium,  calcium, strontium, barium, magnesium and boron, as well as discovering the elemental nature of chlorine and iodine. He also studied the forces involved in these separations, inventing the new field of electrochemistry. Besides the Davy Lamp he invented a very early form of the incandescent light bulb.

Davy was born in Penzance in Cornwall but his family moved to Varfell, near Ludgvan, when he was 9, and in term-time Davy boarded with John Tonkin, his mother’s godfather. After Davy’s father died in 1794, Tonkin apprenticed him to John Bingham Borlase, a surgeon with a practice in Penzance. In the apothecary’s dispensary, Davy became a chemist, and he conducted his earliest chemical experiments in a garret in Tonkin’s house. Davy’s friends said: “This boy Humphry is incorrigible. He will blow us all into the air.” His elder sister complained of the ravages made on her dresses by corrosive substances.

His Quaker friend and mentor Robert Dunkin remarked: ‘I tell thee what, Humphry, thou art the most quibbling hand at a dispute I ever met with in my life.’ One winter day he took Davy to a river to show him that rubbing two plates of ice together developed sufficient energy by motion, to melt them, and that after the motion was suspended, the pieces were united by regelation. Later, as professor at the Royal Institution, Davy repeated many of the ingenious experiments he learned from Dunkin.

Through a mutual friend he met Dr Edwards who was a lecturer in chemistry at St. Bartholomew’s Hospital (Barts). He permitted Davy to use his laboratory and possibly directed his attention to the floodgates of the port of Hayle, which were rapidly decaying as a result of the contact between copper and iron under the influence of seawater. Galvanic corrosion was not understood at that time, but the phenomenon prepared Davy for subsequent experiments on ship’s copper sheathing.

Thomas Beddoes and John Hailstone were engaged in a geological controversy on the rival merits of the Plutonian and Neptunist hypotheses. They traveled together to examine the Cornish coast for evidence of their competing theories and made Davy’s acquaintance. Beddoes, who had established at Bristol a ‘Pneumatic Institution,’ needed an assistant to superintend the laboratory. After prolonged negotiations, mainly by Gilbert, Mrs Davy and Borlase consented to Davy’s departure, but Tonkin wished him to remain in his native town as a surgeon, and altered his will when he found that Davy insisted on going to Dr Beddoes.On 2 October 1798, Davy joined the Pneumatic Institution at Bristol. It had been established to investigate the medical powers of factitious airs and gases, and Davy was to superintend the various experiments. The arrangement agreed between Dr Beddoes and Davy was liberal and enabled Davy to give up all claims on his paternal property in favor of his mother. He did not intend to abandon the medical profession and was determined to study and graduate at Edinburgh but he soon began to fill parts of the institution with voltaic batteries. While living in Bristol, Davy met the Earl of Durham, who was a resident in the institution for his health and became close friends with Gregory Watt, James Watt, Samuel Taylor Coleridge and Robert Southey, all of whom became regular users of nitrous oxide, to which Davy became addicted.


James Watt built a portable gas chamber to facilitate Davy’s experiments with the inhalation of nitrous oxide. At one point the gas was combined with wine to judge its efficacy as a cure for hangover (his laboratory notebook indicated success). The gas was popular among Davy’s friends and acquaintances, and he noted that it might be useful for performing surgical operations. However, anesthetics were not regularly used in medicine or dentistry until decades after Davy’s death. Davy conducted numerous experiments on himself with nitrous oxide, carbon monoxide, and with respiration at considerable risk.

In 1799, Count Rumford had proposed the establishment in London of an ‘Institution for Diffusing Knowledge’ that is, the Royal Institution. In 1801 Davy left Bristol to take up a new post at the Royal Institution as assistant lecturer in chemistry, director of the chemical laboratory, and assistant editor of the journals of the institution.  On 25 April 1801, Davy gave his first lecture on the relatively new subject of ‘Galvanism’. The first lecture garnered rave reviews, and by the June lecture Davy wrote to John King that his last lecture had attendance of nearly 500 people. “There was Respiration, Nitrous Oxide, and unbounded Applause. Amen!”


Davy’s lectures also included spectacular and sometimes dangerous chemical demonstrations for his audience, a generous helping of references to divine creation, and genuine scientific information. Not only a popular lecturer, the young and handsome Davy acquired a huge female following around London, and nearly half of the attendees pictured in Gillray’s cartoon of the Royal Institution are female. When Davy’s lecture series on Galvanism ended, he progressed to a new series on Agricultural Chemistry, and his popularity continued to skyrocket. By June 1802, after just over a year at the Institution and at the age of 23, Davy was nominated to full lecturer.

In 1802 Davy had what was then the most powerful electrical battery in the world at the Royal Institution. With it, Davy created the first incandescent light by passing electric current through a thin strip of platinum, chosen because the metal had an extremely high melting point. It was neither sufficiently bright nor long lasting enough to be of practical use, but demonstrated the principle. By 1806 he was able to demonstrate a much more powerful form of electric lighting to the Royal Society in London. It was an early form of arc light which produced its illumination from an electric arc created between two charcoal rods.


Davy was a pioneer in the field of electrolysis using the voltaic pile to split common compounds and thus prepare many new elements. He went on to electrolyze molten salts and discovered several new metals, including sodium and potassium. Davy discovered potassium in 1807, deriving it from caustic potash (KOH). Before the 19th century, no distinction had been made between potassium and sodium. Potassium was the first metal that was isolated by electrolysis. Davy isolated sodium in the same year by passing an electric current through molten sodium hydroxide. Davy discovered calcium in 1808 by electrolyzing a mixture of lime and mercuric oxide. He worked with electrolysis throughout his life and was first to isolate magnesium, boron, and barium.

Chlorine was discovered in 1774 by Swedish chemist Carl Wilhelm Scheele, who called it “dephlogisticated marine acid” and mistakenly thought it contained oxygen. Davy showed that the acid of Scheele’s substance, called at the time oxymuriatic acid, contained no oxygen. This discovery overturned Lavoisier’s definition of acids as compounds of oxygen. In 1810, chlorine was given its current name by Humphry Davy, who insisted that chlorine was in fact an element.

Davy later damaged his eyesight in a laboratory accident with nitrogen trichloride. Pierre Louis Dulong first prepared this compound in 1812, and lost two fingers and an eye in two separate explosions with it. Davy’s own accident induced him to hire Michael Faraday as a co-worker.

In 1812, Davy was knighted, gave a farewell lecture to the Royal Institution, and married a wealthy widow, Jane Apreece. (While Davy was generally acknowledged as being faithful to his wife, their relationship was stormy, and in later years he travelled to continental Europe alone.) In October 1813, he and his wife, accompanied by Michael Faraday as his scientific assistant (and valet), travelled to France to collect a medal that Napoleon Bonaparte had awarded Davy for his electro-chemical work. While in Paris, Davy was asked by Gay-Lussac to investigate a mysterious substance isolated by Bernard Courtois. Davy showed it to be an element, which is now called iodine. The party left Paris in December 1813, traveling south to Italy. They stayed a while in Florence, where, in a series of experiments conducted with Faraday’s assistance, Davy succeeded in using the sun’s rays to ignite diamond, proving it is composed of pure carbon.

Davy’s party continued to Rome, and also visited Naples and Mount Vesuvius. By June 1814, they were in Milan, where they met Alessandro Volta, and then continued north to Geneva. They returned to Italy via Munich and Innsbruck, and when their plans to travel to Greece and Istanbul were abandoned after Napoleon’s escape from Elba, they returned to England.


After his return to England in 1815, Davy experimented with lamps for use in coal mines. There had been many mining explosions caused by firedamp or methane often ignited by open flames of the lamps then used by miners. In particular the Felling mine disaster in 1812 near Newcastle caused great loss of life, and action was needed to improve underground lighting and especially the lamps used by miners. Davy conceived of using an iron gauze to enclose a lamp’s flame, and so prevent the methane burning inside the lamp from passing out to the general atmosphere. Although the idea of the safety lamp had already been demonstrated by William Reid Clanny and by the then unknown (but later very famous) engineer George Stephenson, Davy’s use of wire gauze to prevent the spread of flame was used by many other inventors in their later designs. George Stephenson’s lamp was very popular in the north-east coalfields, and used the same principle of preventing the flame reaching the general atmosphere, but by different means. Unfortunately, although the new design of gauze lamp initially did seem to offer protection, it gave much less light, and quickly deteriorated in the wet conditions of most pits. Rusting of the gauze quickly made the lamp unsafe, and the number of deaths from firedamp explosions rose yet further.

There was some discussion as to whether Davy had discovered the principles behind his lamp without the help of the work of Smithson Tennant, but it was generally agreed that the work of both men had been independent. Davy refused to patent the lamp, and its invention led to his being awarded the Rumford medal in 1816.

In January 1819, Davy was awarded a baronetcy. Although Sir Francis Bacon and Sir Isaac Newton had already been knighted, this was, at the time, the first such honor ever conferred on a man of science in Britain. A year later he became President of the Royal Society. Davy’s laboratory assistant, Michael Faraday, went on to enhance Davy’s work and would become the more famous and influential scientist. Davy is supposed to have even claimed Faraday as his greatest discovery. Davy later accused Faraday of plagiarism, however, causing Faraday (the first Fullerian Professor of Chemistry) to cease all research in electromagnetism until his mentor’s death.


Davy spent the last months of his life writing Consolations in Travel, an immensely popular, somewhat freeform compendium of poetry, thoughts on science and philosophy. Published posthumously, the work became a staple of both scientific and family libraries for several decades afterward. Davy spent the winter in Rome, hunting in the Campagna on his 50th birthday. But on 20 February 1829 he had a stroke. After spending many months attempting to recuperate, Davy died in a hotel room in Geneva on 29 May 1829.

He had wished to be buried where he died, but had also wanted the burial delayed in case he was only comatose. He refused to allow a post-mortem for similar reasons. But the laws of Geneva did not allow any delay and he was given a public funeral on the following Monday, in the Plainpalais Cemetery, outside the city walls. Jane organized a memorial tablet for him, in Westminster Abbey shortly afterwards.


In the spirit of Davy’s experiments the Royal Institution’s website gives a recipe for microwave cupcakes (or mug cakes) and suggests ways to experiment, Here’s the basic recipe slightly edited.  The point is to make the original first, and then play around with the ingredients and see what happens. RI asks the following questions:

What do you think will happen if we don’t include the egg?

How could we find out?

What do you think will happen if we don’t include the oil?

What do you think will happen if we don’t include the baking


Microwave Mug Cake


4 tbsp plain flour
2 tbsp caster sugar
¼ tsp baking powder
1 small/medium egg
2 tbsp vegetable oil
2 tbsp water


Mix all the dry ingredients together in a mug

Break the egg into the mug and add the oil and water

Stir vigorously with a fork

Zap the resulting mixture in your microwave at full power for 2 minutes


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