English chemist who discovered several chemical elements (including sodium and potassium) and compounds, and became one of the greatest exponents of the scientific method. Davy is best remembered for his contributions to the understanding of electrochemistry and for his invention of a safety lamp for miners.
Davy was the elder son of middle-class parents, who owned an estate in Ludgvan. He was educated at the grammar school innearby Penzance and, in 1793, at Truro. In 1795, a year after the death of his father, Robert, he was apprenticed to a surgeon and apothecary, J. Binghan Borlase, and he hoped eventually to qualify in medicine.
An exuberant, affectionate, and popular lad, of quick wit and lively imagination, he was fond of composing verses, sketching, making fireworks, fishing, shooting, and collecting minerals. He loved to wander, one pocket filled with fishing tackle and the other with rock specimens; he never lost his intense love of nature and, particularly, of mountain and water scenery.
While still a youth, ingenuous and somewhat impetuous, Davy had plans for a volume of poems, but he began the serious study of science in 1797, and these visions “fled before the voice of truth.” After reading Antoine Lavoisier’s “Traite Elementaire”, Davy in 1797 became interested in chemistry.
He was befriended by Davies Giddy (later Gilbert; president of the Royal Society, 1827-30), who offered him the use of his library in Tradea and took him to a chemistry laboratory that was well equipped for that day. There he formed strongly independent views on topics of the moment, such as the nature of heat, light, and electricity and the chemical and physical doctrines of A.-L. Lavoisier.
In his small private laboratory, he prepared and inhaled nitrous oxide (laughing gas), in order to test a claim that it was the “principle of contagion,” that is, caused diseases. On Gilbert’s recommendation, he was appointed (1798) chemical superintendent of the Pneumatic Institution, founded at Clifton to inquire into the possible therapeutic uses of various gases. Davy attacked the problem with characteristic enthusiasm, evincing an outstanding talent for experimental inquiry.
He investigated the composition of the oxides and acids of nitrogen, as well as ammonia, and persuaded his scientific and literary friends, including Samuel Taylor Coleridge, Robert Southey, and P.M. Roget, to report the effects of inhaling nitrous oxide. He nearly lost his own life inhaling water gas, a mixture of hydrogen and carbon monoxide sometimes used as fuel. The account of his work, published as Researches, Chemical and Philosophical (1800), immediately established his reputation, and he was invited to lecture at the newly founded Royal Institution of Great Britain in London, where he moved in 1801, with the promise of help from the British-American scientist Sir Benjamin Thompson (Count von Rumford), the British naturalist Sir Joseph Banks, and the English chemist and physicist Henry Cavendish in furthering his researches; e.g., on voltaic cells, early forms of electric batteries. His carefully prepared and rehearsed lectures rapidly became important social functions and added greatly to the prestige of science and the institution.
In 1802 he became professor of chemistry. His duties included a special study of tanning: he found catechu, the extract of a tropical plant, as effective as and cheaper than the usual oak extracts, and his published account was long used as a tanner’s guide. In 1803 he was admitted a fellow of the Royal Society and an honorary member of the Dublin Society and delivered the first of an annual series of lectures before the board of agriculture. This led to his Elements of Agricultural Chemistry (1813), the only systematic work available for many years. For his researches on voltaic cells, tanning, and mineral analysis, he received the Copley Medal in 1805. He was elected secretary of the Royal Society in 1807.
Davy’s chemical lectures and demonstrations were brilliantly presented and became a fashionable social event. He also lectured and wrote a book on agricultural chemistry and presented the first systematic geology course offered in England. His first Bakerian Lecture won a prize from Napoleon, even though France and England were at war.
A young Humphry Davy gleefully works the bellows in this caricature by James Gillray of experiments with laughing gas at the Royal Institution. The Lecturer is Thomas Garret, Davy’s predecessor as professor of chemistry. Benjamin Thompson, Count Rumford, the founder of the Royal Institution, stands at the doorway.
Davy early concluded that the production of electricity in simple electrolytic cells resulted from chemical action and that chemical combination occurred between substances of opposite charge. He therefore reasoned that electrolysis, the interactions of electric currents with chemical compounds, offered the most likely means of decomposing all substances to their elements. These views were explained in 1806 in his lecture “On Some Chemical Agencies of Electricity,” for which, despite the fact that England and France were at war, he received the Napoleon Prize from the Institut de France (1807).
This work led directly to the isolation of sodium and potassium from their compounds (1807) and of the alkaline-earth metals from theirs (1808). He also discovered boron (by heating borax with potassium), hydrogen telluride, and hydrogen phosphide (phosphine). He showed the correct relation of chlorine to hydrochloric acid and the untenability of the earlier name (oxymuriatic acid) for chlorine; this negated Lavoisier’s theory that all acids contained oxygen. He explained the bleaching action of chlorine (through its liberation of oxygen from water) and discovered two of its oxides (1811 and 1815), but his views on the nature of chlorine were disputed. He was not aware that chlorine is a chemical element, and experiments designed to reveal oxygen in chlorine failed.
In 1810 and 1811 he lectured to large audiences at Dublin (on agricultural chemistry, the elements of chemical philosophy, geology) and received $1,275 in fees, as well as the honorary degree of LL.D., from Trinity College. In 1812 he was knighted by the Prince Regent (April 8), delivered a farewell lecture to members of the Royal Institution (April 9), and married Jane Apreece, a wealthy widow well known in social and literary circles in England and Scotland (April 11). He also published the first part of the Elements of Chemical Philosophy, which contained much of his own work; his plan was too ambitious, however, and nothing further appeared. Its completion, according to a Swedish chemist, J.J. Berzelius, would have “advanced the science of chemistry a full century.”
His last important act at the Royal Institution, of which he remained honorary professor, was to interview the young Michael Faraday, later to become one of England’s great scientists, who became laboratory assistant there in 1813 and accompanied the Davys on a European tour (1813-15). By permission of Napoleon, he travelled through France, meeting many prominent scientists, and was presented to the empress Marie Louise. With the aid of a small portable laboratory and of various institutions in France and Italy, he investigated the substance “X” (later called iodine), whose properties and similarity to chlorine he quickly discovered; further work on various compounds of iodine and chlorine was done before he reached Rome. He also analyzed many specimens of classical pigments and proved that diamond is a form of carbon.
The Oxides of Nitrogen
When Davy was released from his indenture as a apprentice, he became superintendent of the Medical Pneumatic Institution of Bristol. This organization was devoted to the study of the medical value of various gases, and it was here that Davy first made his reputation. He studied the oxides of nitrogen and discovered the physiological effects of nitrous oxide, which became known as laughing gas. He “breathed 16 quarts of the gas in seven minutes” and became “completely intoxicated” with it. It would be forty-five years later before nitrous oxide would be used as a anesthetic by dentists.
From a notebook that he kept at this time are analytical results that document the discovery of nitrous oxide and that illustrate the law of multiple proportions:
The ratios in the last column are proportional to 1:1.88:4.13. (The compounds analyzed are NO2, NO, and N2O.) Today we see in data such as these a confirmation of one tenet of Dalton’s atomic theory: Compounds consist of atoms of their constituent elements combined in small whole number ratios. But at this time Davy dismissed Dalton’s theory as “rather more ingenious than important.” To Dalton’s claim that “chemical analysis and synthesis go no farther than to the separation of particles one from another, and their reunion. No new destruction or creation of matter is within the reach of chemical agency”, Davy replied: “There is no reason to suppose that any real indestructible principle
has yet been discovered.”
Electrolysis and the Alkali Metals
Davy’s next and most important investigations were devoted to electrochemistry. Following Galvani’s experiments and the discovery of the voltaic pile, interest in galvanic electricity had become widespread. The first chemical decomposition by means of the pile was carried out in 1800 by Nicholson and Carlisle, who obtained hydrogen and oxygen from water, and who decomposed the aqueous solutions of a variety of common salts. Davy, too, began to example the chemical effects of electricity in 1800.
He soon found that when he passed electrical current through some substances, these substances decomposed, (a process later called electrolysis). Thus it was certain that electrical forces could act (generate current) only when the electrolyte was capable of oxidizing one of the metals, and that the intensity of its effect (the voltage generated) was directly related to the reactivity of the electrolyte with the metal. Evidently, Davy understood that the actions of electrolysis and of the voltaic pile were the same. His work led him to propose that the elements of a chemical compound are held together by electrical forces:
“In the present state of our knowledge, it would be useless to attempt to speculate on the remote cause of the electrical energy . . . ; its relation to chemical affinity is, however, sufficiently evident. May it not be identical with it, and an essential property of matter?”
Davy must have known of Lavoisier’s suggestion that the alkali earths were oxides of unknown metals. At first, he tried to separate the metals by electrolyzing aqueous solutions of the alkalis, but this yielded only hydrogen gas. He then tried passing current through molten compounds, and his persistence was rewarded when he was able to separate globules of pure metal by this means. His first successes came in 1807 with the separation of potassium from molten potash and of sodium from common salt.
He described potassium as particles which, when thrown into water, “skimmed about excitedly with a hissing sound, and soon burned with a lovely lavender light.” Dr. John Davy, Humphry’s brother, said that Humphry “danced around and was delirious with joy” at his discovery. These results were presented in the Bakerian lecture of November, 1807.
Through electrolysis, Davy eventually discovered magnesium (Magnesia, a district in Thessaly), calcium (calx, L for lime), strontium, and barium in 1808. For all these discoveries, much groundwork had of course been done by others. Thus, Scheele had distinguished baryta from lime in 1774, and Berzelius and Pontin had prepared calcium amalgam by electrolyzing lime in mercury. But Davy was able to isolate the pure metals. Davy utilized the reducing power of potassium to prepare boron, and he developed the method of separating potassium from sodium based upon the insolubility of potassium perchlorate and the solubility of sodium perchlorate in 97% alcohol.
Davy’s research on chlorine is of an importance comparable with those on the alkali metals. Chlorine was first isolated by the Swedish chemist Carl Wilhelm Scheele (1742-1786) in 1774. Scheele did not regard this pungent green gas as an element. He referred to it as “dephlogisticated marine acid”. To Scheele, phlogiston was practically synonymous with hydrogen, so in a curious sense, his view of chlorine was essentially correct. Lavoisier, however, chiefly occupied with phenomena of combustion, assumed that chlorine was an oxide of an unknown “radical”. Davy performed many experiments to confirm the presence of oxygen.
He reacted “oxymuriatic acid”, as the English called it, with ammonia, and found only muriatic acid and nitrogen in the products:
3 Cl2 + 2 NH3 ——> 6 HCl + N2
He exposed the gas to white-hot carbon in an attempt to remove the oxygen as carbon dioxide. He was never able to produce oxygen or any compound known to contain oxygen, and he finally concluded that it was an element. He called it “chlorine” after the Greek “chloros” meaning yellow-green, the same association with color as found in “chlorophyll”. By a similar series of experiments, Davy showed in 1810 that muriatic acid or marine acid was a compound only of hydrogen and chlorine, and contained no oxygen. For example, he found that two volumes of muriatic acid react with mercury to give calomel and one volume of hydrogen:
2 HCl + 2 Hg ——> Hg2Cl2 + H2
This put an end to Lavoisier’s theory that oxygen was an essential constituent of acids.
Iodine was first prepared in 1811 by Bernard Courtois (1777-1838) who observed purple vapors rising from kelp ashes that he had acidified with sulfuric acid and heated. The purple vapors condensed on a cold surface, forming nearly black crystals. Others, notably Joseph Gay-Lussac and Humphry Davy, proved that the crystals were an element, and it was named after the Greek iodes, meaning violet. Davy first made iodine pentoxide, a colorless, odorless, crystalline substance of high density in 1815. It is a strong oxidizing agent, and with oxidizible substances sometimes detonates.
I2O5 + 10 H+ + 10 e- ——> I2 + 5 HOH
Davy developed the method for the decomposition of silicates into silica by treatment with hot HCl.
SiO44- + 4 H+ ——> SiO2 + 2 HOH
Davy was evidently the first to observe that platinum induced the oxidation of alcohol vapor in air.
In 1799, Davy did an experiment which showed that when two pieces of ice (or other substance with a low melting point) were rubbed together they could be melted without any other addition of heat. This experiment provided evidence that helped to disprove the caloric theory of heat. In 1802, Thomas Wedgwood in cooperation with Sir Humphry Davy published a paper entitled “An Account of a Method of Copying Paintings on Glass, and Making Profiles, by the Agency of Light upon Nitrates of Silver”. The pictures made by this process were very temporary.
As soon as the negatives were removed the pictures turned black. Among Davy’s other accomplishments are the introduction of a chemical approach to agriculture and the tanning and mineralogy industries. He designed an Arc Lamp and invented a process that could be used to desalinate sea water. He also designed a method whereby copper-clad ships could be protected by having zinc plates connected to them.
Shortly after his return, he studied, for the Society for Preventing Accidents in Coal Mines, the conditions under which mixtures of firedamp and air explode. This led to the invention of the miner’s safety lamp and to subsequent researches on flame, for which he received the Rumford medals (gold and silver) from the Royal Society and, from the northern mine owners, a service of plate (eventually sold to found the Davy Medal).
The basic principle of the safety lamp is, that the flame is covered by a gauze with certain meshes per square inch. On November 1, 1816 Davy wrote in a letter to the Royal Society: “This invention consists in covering or surrounding the flame of a lamp or a candle by a wire sieve”.
The wire sieve was fitted with 625 apertures in a square inch and the wire was 1/70 inch thick. Davy didn’t ask for a patent. He earned the merit to have saved miner’s life through his efforts in inventing safer lights. Davy wrote 1816: “No, my good friend, I never thought of such a thing; my sole object was to serve the cause of humanity, and if I succeeded I am amply rewarded in the gratifying of having done so”.
After being created a baronet in 1818, he again went to Italy, inquiring into volcanic action and trying unsuccessfully to find a way of unrolling the papyri found at Herculaneum. In 1820 he became president of the Royal Society, a position he held until 1827. In 1823-25 he was associated with the politician and writer John Wilson Croker in founding the Athenaeum Club, of which he was an original trustee, and with the colonial governor Sir Thomas Stamford Raffles in founding the Zoological Society and in furthering the scheme for zoological gardens in Regent’s Park, London (opened in 1828).
During this period, he examined magnetic phenomena caused by electricity and electrochemical methods for preventing saltwater corrosion of copper sheathing on ships by means of iron and zinc plates. Though the protective principles were made clear, considerable fouling occurred, and the method’s failure greatly vexed him. But he was, as he said, “burned out.” His Bakerian lecture for 1826, “On the Relation of Electrical and Chemical Changes,” contained his last known thoughts on electrochemistry and earned him the Royal Society’s Royal Medal.
Association with Michael Faraday
In 1801, the Royal Institution in London engaged Davy as a public lecturer. Michael Faraday (1791-1867) began attending Davy’s lectures in 1810. In December, 1811, Faraday impressed Davy by sending him copious bound notes of these lectures, including exact drawing of Davy’s apparatus. The previous October, Davy had been temporarily blinded by an explosion in his laboratory, and he needed help. He hired Faraday at once, beginning a close personal and professional association that lasted for years. Davy twice opposed the election of Faraday to fellowship in the Royal Society.
At one point he objected to honoring Faraday for achieving the first liquefication of chlorine, claiming that he himself deserved credit for the feat. Another time, Davy said his opposition was due to his belief that William Wollaston (1766-1828) had preceded Faraday in discovering electromagnetic rotation. Perhaps Davy had simply become envious of his (successful) former assistant. Faraday did finally become a Fellow of the Royal Society in 1824.
In 1827, Davy became seriously ill. The illness was later attributed to his inhalation of many gases over the years. Davy’s health was by then failing rapidly; in 1827 he departed for Europe and, in the summer, was forced to resign the presidency of the Royal Society, being succeeded by Davies Gilbert. Having to forgo business and field sports, Davy wrote Salmonia: or Days of Fly Fishing (1828), a book on fishing (after the manner of Izaak Walton) that contained engravings from his own drawings.
After a last, short visit to England, he returned to Italy, settling at Rome in February 1829–”a ruin amongst ruins.” Though partly paralyzed through stroke, he spent his last months writing a series of dialogues, published posthumously as Consolations in Travel, or the Last Days of a Philosopher (1830). While in Rome, he had a heart attack and he later died on May 29, 1829 in Geneva, Switzerland.
Humphry Davy Medal, The Royal Society, London
The award is made annually for an outstandingly important recent discovery in any branch of chemistry. The medal is made of bronze and the winner also receives a gift of $1000.