ENGRAVING: NATIONAL LIBRARY OF MEDICINE T r Thomas Beddoes, aphysicianand friends oftheyounger Watt, Davy met ry In A GaseousPhase of hisday. book, Davy aspired tobetheIsaac Newton for himself. Asheindicated inhisnote- he begantoimagineagreat career inscience er’s classic by reading AntoineLavoisi-of chemistry which hewouldpursuethroughout hislife. D to mathematics.From hisearliestyears, from theologytophysics,botany everything o university education,butDavy devisedhis apothecaries were notrequired tohave a in Penzance. At thattime,surgeonsand B to work, beginninganapprenticeship with tence. In 1795,16-year-old Humphry went allow herorthechildren aleisurely exis- but thefamily’s reduced incomewouldnot years, shopforafew er operatedamillinery the ageof48,in1794.Humphry’s moth- five children. was thefirstofRobert andhiswifeGrace’s of independentyeoman farmers.Humphry descendedfrom generations a woodcarver Cornwall, England. His father, Robert, was ber 17,1778,inthetown ofPenzance, chemistry. of themostfamousnamesinEuropean surgeon’s apprentice andendeditasone world. He beganhiscareer asahumble © Richard A.Pizzi discovery rosefromhumblebeginnings. T Self-Made Chemist Humphry Davy, esearcher atthePneumatic Institution 2004 A wn program ofself-education,reading ingham Borlase,anapothecary-surgeon his pioneerofelectrochemistryandchemical avy expressed broad intellectualinterests,

1798, Davy becamefriendly withGrego- Wa At R Hu obert Davy diedrelativelyobert young, at

the ageof18,Davy beganhisstudy mphry Davy wasbornonDecem- mphry tt, sonofJames Watt. Through MERICAN first professional scientistsinthe S he English chemistandinventor ir Humphry Davy wasoneofthe E lements ofChemistry C HEMICAL S OCIETY . Already, by 50 years thefirstuse of thegasonpatients effects ofnitrous oxide preceded by almost 7 minutesanddescribeditseffects indetail. sition. He ofthegasin inhaled16quarts andcompo- mined itschemicalproperties obtained thegasinapure stateanddeter- tried breathing it. Within amonth, Davy pr He the physiologicaleffectsofsubstance. these inquiriesinanattempttodetermine ered by Joseph Priestley. Davy continued called “laughinggas”, whichwasfirstdiscov- nitrous oxide, orwhatwouldcometobe of various gases. devoted tothestudyofmedicalvalue as anassistantattheInstitution, whichwas his medicalapprenticeship andhired him ing, Beddoes arrangedtorelease himfrom near Bristol. Impressed withDavy’s think- exemplify thedangersinherent in 18thand i upr ay 1778–1829. Sir HumphryDavy,

dentists. Davy’s experimentsonhimself D B eddoes hadbeenexperimentingwith avy’s oftheanesthetic observations epared impure samplesofthegasand trolyte couldoxidize oneofthemetals,and could generatecurrent only whentheelec- tical. He thatelectrical forces ascertained of thevoltaic pileandelectrolysis were iden- work, Davy determinedthattheactions later termedelectrolysis. Asaresult of his substances decomposed. This process was current through somesubstances,the discovered thatwhenhepassedelectrical stimulate achemicalreaction. and thatinturnanelectriccurrent could a chemicalreaction generatedthecurrent, contact ofmetals.Instead, hethoughtthat that electricitywasgeneratedsimplyby the common salts.Davy disagreed with Volta decomposed thesolutionsofavariety of and oxygen from waterandsuccessfully experiment. They obtainedhydrogen Anthony CarlisleinLondonrepeated Volta’s to thecontactofdissimilarmetals. got electricityandattributedtheeffects between them.From this“voltaic pile” he ent metalswithdampcardboard layers imented witha“pile” ofdiskstwodiffer- than generatedelectricity. Volta hadexper- claiming thatanimaltissuesdetectedrather tissues generatedelectricity. Volta demurred, istry. Galvani inanimal believed thatnerves ated widespread interest inelectrochem- Lu istry. experimentsof The 18th-century tigations were inthefieldofelectrochem- inves- next andultimatelymostimportant r tation asascientificstar, fastgainingthe D course, rewards camewiththerisks. would takeatollonDavy’s health,butof substances. Ultimately, suchrisk-taking precautionstook few withunknown science.Researchers19th century likeDavy espect ofhisfellow chemists. avy wasbeginningtoestablisharepu- igi Galvani andAlessandro Volta gener- D In After hiswork withnitrous oxide, Davy’s avy initiatedhisown experimentsand

A 1800, William Nicholson and PRIL CHRONICLES CHEMISTRY 2004 T ODAY ’ S C EITAT HEMIST W ORK 49 CHEMISTRY CHRONICLES that the voltage generated was directly relat- the meantime, he had accepted an appoint- rate pure metals by passing current through ed to the reactivity of the electrolyte with ment at the Royal Institution in London. molten compounds. In 1807, he separat- the metal. Davy also discovered that metals Thus, he was recognized as one of the lead- ed potassium from molten potash and sodi- were not necessary, as he made a pile ing lights of British science. um from common salt. When observing with zinc and charcoal. The Royal Institution provided Davy potassium particles in water, Davy famous- Davy proposed that electrical forces with significantly more resources than he ly exclaimed that they “skimmed about hold the elements of a chemical compound had at the Pneumatic Institution. He was excitedly with a hissing sound and soon together. In June 1801, he presented a given a bigger voltaic battery with which burned with a lovely lavender light.” He paper to the Royal Society explaining his to perform his experiments. With better presented the results of this experiment work. Two years later, at age 24, he was working conditions, Davy’s innovative in his Bakerian Lecture of 1807. elected a Fellow of the Royal Society. In research continued. He was able to sepa- Chemical Discovery Using electrolysis, Davy in 1808 isolated calcium, barium, strontium, and magne- sium. He used a mercury cathode and was the first to create an alloy with mercury. Davy, however, was not the first to inves- tigate the “alkaline earths”. He was preced- ed by two Swedish scientists: Carl Wilhelm Scheele, who had distinguished baryta from lime in 1774, and J. J. Berzelius, who had prepared a calcium alloy by elec- trolyzing lime in mercury. Davy was the first, however, to isolate the pure metals, though many historians think that Berzelius would eventually have made similar discov- eries. Davy also developed the method of separating potassium from sodium, and he used potassium to prepare boron. Another important aspect of Davy’s career was his research on chlorine. As was the case with the “alkaline earths”, Scheele had anticipated his work in the 18th centu- ry. When Scheele exposed muriatic acid to manganese dioxide, a green gas result- ed. Scheele did not regard the gas as an element but as “dephlogisticated marine acid.” He believed that phlogiston was practically synonymous with hydrogen. Lavoisier, on the other hand, had assumed that the green gas was an oxide of an unknown “radical”. Davy was suspicious of Lavoisier’s theory and performed exper- iments to confirm the presence of oxygen. Davy first combined the green gas, “oxymuriatic acid” as the British called it, with ammonia, but he found only muriat- ic acid and nitrogen. He then exposed it to heated carbon in an attempt to remove the oxygen as carbon dioxide. None of his exper- iments yielded any oxygen or compounds known to contain oxygen, and Davy ulti- mately concluded that the gas was an element. He named it “chlorine” from the Greek word chloros, which means yellow-green. Additional experiments in 1810 revealed that muriatic acid was a compound of hydrogen and chlorine, and contained

50 TODAY’S CHEMIST AT WORK APRIL 2004 www.tcawonline.org no oxygen. Davy’s research on chlorine led greater fame throughout Europe. In 1818 and on May 29 of that year, Davy died of to a rejection of Lavoisier’s theory that he was named a baronet, and in 1820 he a heart attack in Geneva, leaving a scien- oxygen was an essential constituent of acids. was appointed President of the Royal Soci- tific legacy that few have been able to match. The year 1810 was also an important ety, an office he held for seven years. As one in British science for a less obvious successful as he was, however, in the mid- Further Reading reason. It was the first year a young Michael 1820s Davy’s health began to deteriorate. Knight, D. Humphry Davy: Science & Power; Cambridge Faraday began attending Davy’s lectures at He became seriously ill in 1827 and moved University Press: Cambridge, U.K., 1998. Humphry Davy; www.chemheritage.org/Educational the Royal Institution. In 1813, Davy hired to Rome in 1828. Much of his ill health Services/chemach/eei/hd.html. Faraday as an assistant, the first step in a was later attributed to the inhalation of professional and personal relationship that toxic gases over the course of a long career. Richard A. Pizzi is a freelance writer with an M.A. in lasted many years. In the winter of 1829 he had a stroke, history from the University of Florida. ◆ Davy was knighted by King George III in 1812; that same year, he married Jane Apreece, a wealthy widow from a promi- nent family. Now financially comfortable, Davy ceased lecturing at the Royal Institu- tion, but he was granted the title Honorary Professor of Chemistry and continued to use the Institution’s laboratory for his research. He also served as Secretary of the Royal Society and undertook two lecture tours of Ireland. Davy was now one of the most famous scientists in the world.

The Safety Lamp While touring Europe in 1813 with his wife and Faraday, Davy was contacted by Sir Ralph Milbanke of the Society for Preventing Accidents in Coal Mines. This organization, founded under the auspices of the Duke of Northumberland, wanted Davy to develop a safety lamp for coal miners to wear on their helmets. Back in England in 1815, Davy agreed to work on the development of a safety lamp that would not ignite the methane-heavy air in the mines. He visited many collieries in northern England and returned from Hebburn Colliery with samples of “firedamp” taken in wine bottles. In October 1815, Davy discovered that, in his own words, “explosive mixtures of minedamp will not pass through small aper- tures or tubes, and that if a lamp . . . be made air-tight on the sides and furnished with apertures to admit the air, it will not communicate flame to the outward atmo- sphere.” A few months later, in early 1816, the first Davy lamps were tested at Hebburn Colliery. The success of Davy’s safety lamp, which consisted of a candle or lamp flame surrounded by a wire sieve, revolution- ized the mining industry. Although William Clanny and George Stephenson both devel- oped similar lamps in the early 19th centu- ry, Davy is credited with inventing the first working safety lamp. The safety lamp brought Davy even www.tcawonline.org APRIL 2004 TODAY’S CHEMIST AT WORK 51