Redis co very of the Elements - Department of Chemistry

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Rediscovery of the ElementsSir Humphry Davy and the Alkalis

James L. Marshall, Beta Eta 1971, andVirginia R. Marshall, Beta Eta 2003,Department of Chemistry, University ofNorth Texas, Denton, TX 76203-5070,[email protected]

In a previous HEXAGON article on JosephBlack,1h the three alkalis known in the 1700swere listed: “vegetable alkali” (potash), “mineralalkali” (soda), and “volatile alkali” (ammonia).1h

All were known to react vigorously with acidsand “to change the color of syrup of violets togreen.” Ammonia was apparently a compoundof nitrogen and hydrogen,2d as shown byClaude Louis Berthollet (1748–1822) at hisfamous laboratory at Arcueil.1c It was natural,therefore, that Antoine-Laurent Lavoisier(1743–1794) himself, the “father of modernchemistry,”1b who first recognized the true ele-ments and listed 31 that are now found in thePeriodic Table,3 would exclude the “fixed alka-lis” —potash and soda—from his list,3 becausethey might be compounds of nitrogen as well.Lavoisier was even unsure of whether potash,produced commercially by the incineration ofplants, existed before possibly being created inthe plants.2c He further speculated that “veg-etable alkali” was synthesized from compo-nents in the atmosphere and “mineral alkali”was formed naturally in the sea.3 The truenature of potash and soda was not clarifieduntil the next century, at the Royal Institution inLondon (Figures 1, 2).

The distinction between potassium andsodium. Henri-Louis Duhamel du Monceau(1700–1782) was the first to differentiate clear-

ly between “vegetable alkali” and “mineralalkali.”2b Duhamel was a botanist; he devel-oped an agricultural/forestry farm atDenainvilliers, a suburb of Pithiviers (75 kmsouth of Paris). Duhamel showed in 1736 thatthe salts of the two alkalis, as prepared frommineral acids, differ in crystalline form, solubil-ity, and taste. (Today mineralogists describehow “sylvite” (KCl) at Death Valley, California,is the last to precipitate out and tends to formgranular masses compared to the distinctive

cubic “halite” (NaCl) crystals; persons taking“low-sodium” salt in their diet are acquaintedwith the more bitter, astringent taste of KCl.)Duhamel further showed that the alkali com-ponent common salt (sodium chloride) is iden-tical with the alkali of Egyptian natron (sodiumcarbonate), and of borax (sodium borate).2b

Duhamel’s estate still exists, complete with hischateau and the original ventilated silo,designed by him and reputed to be the firstever constructed (Figure 3).

Figure 1. Royal Institution, 21 Albemarle St. (N51° 30.58 W00° 08.55), was founded in 1799 and has notchanged its location since. The Institution was founded by Sir Benjamin Thompson, Count Rumford(1753–1814), an American born British scientist who through observing the boring of cannons realizedheat was created by friction.10,11a

His colorful history included his 1804marriage to Marie-Anne Lavoisier, thewidow of the famous Antoine Lavoisier.11a

Figure 2. Royal Institution, appearance in1838 (painting by Thomas H. Shepherd,1793–1864). At this time MichaelFaraday was prominent among its scien-tists, having succeeded Humphry Davy,who was the first to prepare elementalpotassium and sodium here in 1807.10

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Two decades after Duhamel’s work, Berlinchemist Andreas Sigismund Marggraf (1709–1782), reproduced Duhamel’s work and furtherdifferentiated “vegetable alkali” and “mineralalkali.”1g He prepared the saltpetres (nitrates) ofeach with nitric acid and demonstrated (1758)that “cubic saltpetre” (sodium nitrate) flashedyellow with charcoal and “prismatic saltpetre”(potassium nitrate) flashed blue-violet. Thesecolors are the same as those observed in intro-ductory chemistry classes by dropping metallicsodium and potassium into water.

The derivation of the names sodium andpotassium. On the coasts of the MediterraneanBasin and Western Europe, there exists a scrub-by tidal plant named saltwort, with the generic

name Salsola (meaning “salty”), given byLinneaus in 1753.4 This thistle-like plant wasburned in trenches by the seashore to producealkali economically. Of this genus, twospecies—S. soda and S. kali—were commonsources of alkali. The “kali” was derived fromArabic “qily” meaning “ashes,” and “soda” wasderived from the Italian word for saltwort, ulti-mately derived from the Arabic “suwwad.”Although incinerated plants generally pro-duced “vegetable alkali,” it was observed (e.g.,by Duhamel) that Salsola could give either kindof alkali, and if Salsola was grown very close tothe brackish water then“mineral alkali” was themain ash.2b

The adoption of the names “soda” and“potash” for “mineral alkali” and “vegetable

alkali” occurred during the 17th and 18th cen-turies. Early references (1690) to “soda” include“soude”2a by Nicolas Lemery (1645–1715), theadvocate of the corpuscular theory of “pointyparticles” for acids and “spongy particles” forbases.1g From the ashes of burned wood came“pot-ash,” prepared by boiling the ashes inmetallic pots. The name “potash” originatedfrom the German Pottasche, and was approvedby the Académie francaise in 1762.2b

By the beginning of the 19th century the dis-tinction between sodium and potassium com-pounds was clear, and each was now recog-nized as an element2f —in his lecture notes of1806 John Dalton (1766–1844) recognized“soda” and “potash,” and assigned each with itsrespective atomic weight5 (28 and 42; modernvalues 22.99 and 39.10). But no one had ever“seen” the elements in uncombined form.

Humphry Davy (1778–1829). The first personto prepare the alkalis in elemental form wasHumphry Davy, at the Royal Institution inLondon, in 1807.6b,7 Humphry Davy (Figure 4)was born in Penzance in Cornwall (Figure 5). Asa youth he was an alert and curious student; hisfirst love was roaming about the countrysideobserving nature, the community, and the fish-ers and the tin miners. Drawing from the talesand ghost stories of his aunts and grandmoth-er, he could tell stories that spellbound thecommon folks of Cornwall. This ability to capti-vate an audience was to prove beneficial laterwhen he presented public lectures on science atthe Royal Institution.7 Davy was a visionary; ashe admitted himself, he preferred to “invent,rather than imitate.”8 As he rose through theranks of the scholars, he became the mostwidely known scientific figure in the BritishIsles, if not also on the Continent.7

Figure 4. Upon entering the Royal Institution, inthe hallway is this portrait of Davy by Sir ThomasLawrence (1769–1830), dated 1821. Davy joinedthe Royal Institution in 1801. By the method ofelectrolysis he was the first to prepare metallicpotassium and sodium, and went on to preparestrontium, barium, calcium, magnesium, lithium,and boron. He was the first to recognize the elemental nature of chlorine and iodine.

Figure 3. Duhamel’s estate, complete with vented silo (left).13 Rue Duhamel du Moncean, Denainvilliers,France (N48° 9.02 E02° 14.47). Courtesy, Wikipedia Commons, public domain.

Figure 5. Statue of Humphry Davy at Market JewStreet, Penzance, Cornwall (N50° 07.14 W05°32.18). Davy never forgot his roots in Cornwalland contributed scientific researches directed to thesafety of the tin miners in the area.

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The preparation of elemental potassiumand sodium. Alessandro Volta (1745–1827) in1799 invented the voltaic pile or galvanicpile—the first electric battery (Figure 6). Hisannouncement was communicated to theRoyal Society of London in 1800, and the wordof this new source of electricity spread rapidly,allowing research to develop in many newdirections. It was quickly discovered that thevoltaic pile could decompose substances; one ofDavy’s original findings was that water could bedecomposed into hydrogen and oxygen in twoseparate vessels connected only by a conduc-tor.7 Turning to the alkalis, he attempteddecomposing potassium and sodium, but againcould obtain only hydrogen and oxygen.Reasoning that the water was the source ofthese gases, he tried potash only slightly moist-ened; the result was molten metallic globuleswhich he described as the “peculiar inflamma-ble principle” which was “the basis of potash.”(Figure 7) As he described the experiment, theglobules resembled quicksilver, some of which“burned with explosion and bright flame . . .finally covered with a white film.”6a (He hadobserved the ignition of evolving hydrogen andthe formation of potassium oxide/hydroxide.)We have an eye-witness to the discovery,

Edmund Davy, his cousin, who was acting asassistant: “. . . [Humphry] could not contain hisjoy—he actually bounded about the room inecstatic delight; and some little time wasrequired for him to compose himself sufficientto continue the experiment.”6a A few days laterDavy repeated the experiment to obtain ele-mental sodium. Without a doubt, the elementalproduction of the “fixed” alkalis was the mostfamous of Davy’s discoveries. (Figure 8)

Davy next turned to the alkaline earths.After some unsuccessful attempts, a suggestionby Berzelius (see Figure 6) to use an amalgamallowed the production in 1808 of elementalcalcium, strontium, barium, and magnesium. InDavy’s laboratory, elemental boron (Figures9–11) was produced the same year by reactionof elemental potassium (simultaneously withGay-Lussac, vide infra); and elemental lithiumwas prepared in Davy’s laboratory in 1817promptly after its discovery by Johan AugustArfwedson (1792–1841) in Sweden.1d

Joseph Louis Gay-Lussac (1778–1850). ThisFrench chemist, with Friedrich WilhelmHeinrich Alexander von Humboldt (1769–1859),determined the composition of atmospheric airat the famous laboratory at Arcueil,6b described

in a previous HEXAGON article.1c Gay-Lussacmoved on to l’École polytechnique in Paris,where he co-discovered boron.6b He and LouisJacques Thénard (1777–1857) (the discoverer ofhydrogen peroxide) at l’ École polytechniquesuggested that potassium and sodium wererespective compounds of potash and soda withhydrogen.6b It remained for Davy to demon-strate the hydrogen was generated from resid-ual water—pure potassium and sodium couldnot be forced to evolve hydrogen, no matterhow savagely they were heated.6b

The rivalry between Davy and Gay-Lussacwas intense. Davy had been awarded a Prize byNapoleon for his electrochemical work,8,9 butGay-Lussac was offended by the presumptivemanner of Davy and was displeased by Davy’staking on the “iodine problem” which he hadbeen studying for two years.8 As described in aprevious HEXAGON article,1e this new sub-stance, discovered by Bernard Courtois(1777–1838) in 1811, was a most confusingmaterial—it looked like a metal, but dissolvedin ether! When Davy visited Paris in 1813, herecognized the new substance as an elementand named it“iodine” in analogy to the chlorinefamily to which he ascribed it—much to theconsternation of the scooped Gay-Lussac, who

Figure 6. Exhibit in the Royal Institution: The slatted box is of the originaldesign of the voltaic pile used by Davy. Typically, he would line up 100 ormore 4- or 6-inch pairs of copper and zinc square plates, immersed in analum/dilute sulfuric acid solution.12 This design was the same as that ofBerzelius, who was conducting galvanic studies before Davy to show thedifferential migration of ionic species.1d The Berzelius museum was visitedby the authors in 2000 and is now closed; it was located across the streetfrom the Swedish Royal Academy of Sciences, Lilla Frescativägen 4A(N59° 22.02 E18° 03.09).

Figure 7. Royal Institution: The bladder to the left was used in Davy's laughing gasexperiments. The item to the extreme right is an electrolysis bowl of 1806 design.

RIGHT: Figure 8. Royal Institution: Original samples ofmetals prepared by Davy.

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had named it “l’iode.”1e The “romantic, qualita-tive” Davy and the “cautious, quantitative” Gay-Lussac ordinarily, in their dual roles, “servedchemistry well;”8 however, Davy could easilyovershadow Gay-Lussac, and the (London)Royal Society delighted in noting (20 January1814) that Gay-Lussac had been trumped:6b

“[Iodine] was discovered about two years ago;but such is the deplorable state of scientific men

in France, that no account of it was publishedtill the arrival of our English philosopher there.”

Other contributions of Davy. The mostimportant discovery of Davy was the alkali andalkaline earth metals, but the most importantinvention was the safety miner’s lamp.8 (Figures12,13) Davy was always mindful of the dangersassociated with the tin mines of his Cornish

homeland (Figure 14)—sometimes the flame ofa lamp would ignite pockets of firedamp(methane) in the deep recesses of the tin mines,with disastrous consequences. Davy’s finalsolution was a lamp surrounded by a wiregauze which would not allow the flame tocome in contact with the explosive gases. Othernotable discoveries of Davy included the effectof laughing gas (nitrous oxide, N2O, discoveredby Joseph Priestley in 1772), suggested by Davyas an anesthesia in surgical operations;8 and thecathodic protection of ships’ hulls by platingwith copper sheets.8

Davy’s fame as a riveting lecturer drewdevoted audiences to the Royal Institution; hisfirst lecture was given in 1801 on “The NewBranch of Philosophy; Galvanism [chemicallyproduced direct-current phenomena].” Thepreeminent Philosophical Magazine reported“Mr. Davy . . . acquitted himself admirably, fromthe sparkling intelligence of his eye, his animat-

Figure 9. The famous California open-pit boron mine (N35° 2.94 W117° 40.98) is located in the MojaveDesert at Boron, 40 miles northeast of Los Angeles. This is the largest borate mine in the world. This depositwas formed 20 million years ago.

Figure 10. The Rio Tinto Borax Visitor Center, Suckow Road, Boron, California (35° 1.79 W117° 41.24),has a large variety of exhibits explaining the history and uses of borax and its derivatives, as well as many fascinating mineral specimens.

Figure 11. In the Borax Visitor Center, this impres-sive crystal of kernite (Na2B4O6(OH)2•3H2O) isdisplayed, with Jenny Marshall present, to show itsenormous size. Ordinarily the only borate in aboron mine is borax (Na2B4O5(OH)4•8H2O), butthis mine is unusual in that it has three additionalminerals: kernite, colemanite (CaB3O4(OH)3•H2O),and ulexite (NaCaB5O6(OH)6•5H2O).

Figure 12. Royal Institution: Davy’s early designsof the safety lamp utilized small holes to cool thegases emanated from oil lamps so that pockets offiredamp would not be ignited.

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ed manner, and the tout ensemble we have nodoubt of his attaining a distinguished emi-nence.”8

Michael Faraday (1791-1867).6c Davy’s devot-ed attendant was Michael Faraday, whom somepeople have described as Davy’s greatest discov-ery. (Figure 15) Davy and Faraday were oppo-site in temperament and class; whereas thebuoyant Davy concentrated on attaining “agentleman’s comprehensive education,”8 theserene Faraday, son of a blacksmith, came tothe Royal Institution with minimal education.He heard his first lecture by Davy in 1812, andthe next year became Davy’s assistant—just intime for the two-year journey to the Continent.Because of Davy’s fame, Napoleon had award-ed him a special medal and invited him to visitFrance, even though the two countries were atwar. Because Davy’s valet was afraid to take thetrip, the threesome, Davy, his wife, and Faraday,took the risky 1813–15 trip. Faraday actuallydoubled as a luggage-bearing attendant;Davy’s wife treated him like a hireling, butDavy was kind. Faraday tolerated the overbear-ing treatment and rose to the occasion; hebrushed shoulders with the most famous scien-tists in France—Gay-Lussac, Ampere, andCuvier, as well as the visiting German scientistHumboldt—and learned much. He even metCount Rumford, the founder of the RoyalInstitution (see Figure 1), who had just separat-ed from his wife, Marie-Anne neé PaulzeLavoisier, the widow of Antoine-LaurentLavoisier who had been guillotined in 1794.8

From his lowly background, Faraday—described as “unmatched” as an example of“self-taught genius”8—rose to fame at theRoyal Institution.8,10 With the barest of mathe-matical skills (he was trained only in algebra),he was the one to develop the concept of theelectromagnetic field, later quantified by JamesClerk Maxwell (1831–1879). He developedelectrochemistry and introduced the termselectrode, anode, cathode, and ion.11b In chem-istry he invented the precursor of the Bunsenburner, discovered benzene, and liquified chlo-rine. In 1825 Faraday instituted the Christmaslectures at the Royal Institution, which contin-ue to this day. (Figure 16) The unit of capaci-tance (farad) was named in his honor.

Epilogue. Why Sodium and PotassiumChloride are not SoCl and PoCl. Dalton pio-neered the concept of atoms to explain chemi-cal reactions, postulating a one-for-one combi-nation of atoms to demonstrate specific sum-mations of weights of the elements to formcompounds. Dalton was color-blind (hence, theterm “daltonism”)1c and it was natural for himto visualize featureless spheres, like clumps ofgrapes, which were differentiated solely by their

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weights, to explain his ideas. While this modelproved essential for a descriptive model of thenano-world and its atomic weights, it proved tobe unwieldly for shorthand descriptions. Forexample, consider Glauber’s salt (modern for-mula Na2SO4•10H2O), which by Dalton’s sym-bolism2f would be rendered as:

(The reader should not be confused by theincorrect stoichiometry; during the early 1800sa sulfate was considered to be SO3, water wasbelieved to be HO, and sodium oxide wasNaO.)

Using equations, Thomas Thomson(1773–1852)2e attempted letter symbols, such asw for oxygen, c for carbon, and h for hydrogen,so that oxalic acid = 4w + 3c + 2h and sugar =5w +3c + 4h [sic].2e,6d Thomson, at theUniversity of Edinburgh, was a most successfulauthor, writing a famous textbook, A System ofChemistry, and the very informative and clearly-written History of Chemistry. Thomson was veryimportant in the early years of the 19th centuryby embracing the new ideas that became mod-ern chemical theory; for example, he was virtu-ally the first non-French antiphlogistinist. Hechampioned the ideas of Dalton that promotedthe concept of an atom-by-atom constructionof the universe. Soon Thomson was using theinitial letters of the names of elements, e.g.,“Po” for potassium.

Meanwhile, Berzelius was refining accurateatomic masses, which proved to be indispens-able a few decades later for the conceptualiza-tion by Mendeleev and Meyer for the periodic-ity of the elements. Berzelius, who discoveredselenium, cerium, silicon, and thorium,1d adopt-ed the “initial letter” symbols of Thomson andused these abbreviated symbols to representthese compounds. With so many examples of“S,”“P,”“O,”“So,” and“Po,” Berzelius toyed withthe idea of symbolizing oxygens with dots andwater with an “Aq.”Glauber’s salt would be rep-resented by:

• •••So S + 10 Aq

But this was visually misleading and madedifficult the balancing of equations by inspec-tion.

Latin names were used more commonly byGermanic nations than by the English or theFrench. Berzelius, for example, used the term

Figure 13. This is a “Cambrian lamp,” a modernreplica of the “Clancy lamp,” the final version ofDavy’s safety lamp. Davy never claimed a patenton the safety lamp, instead developing the designas a charitable gift to the miners of his homecounty. (From the collection of the authors)

Figure 14. A historic tin mine in Cornwall, nearthe Camborne School of Mines, University ofExeter. This cultural heritage site is in Pool, nearRedruth (N50° 13.90 W05° 15.74). Two millenniaago, nearby streams once enjoyed the visit ofRomans, traveling in boats of shallow draft, whocollected tin ore for the home base in Italy.

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“Kalibasis” for the potassium analysis of amaterial. Berzelius substituted the Latinizedsymbols, “Na” (natrium) for “So” and “K” (kali-um) for “Po,” which removed the confusion of“So,”“S,”“Po,” and “O.”

Dalton called Berzelius’ symbols “horrify-ing;”6d it was “unnatural” for scientists to usesymbols other than in a mathematic sense.Even Berzelius himself could not make muchuse of his own invention at first. However, thesymbolism gained greater acceptance after itwas discovered that water contained twohydrogens and one oxygen1c and thus thatone-to-one atomic combinations were not therule. By the mid-1800s, with more accurate rel-ative atomic mass determinations, the Berzeliusformulations were mandated. However, theyoriginally employed superscripts rather thansubscripts, although in the first part of the 20thcentury some texts, particularly those of theFrench, maintained the “superscript” conven-tion.

Thus—we have Berzelius to thank when wewrite such formulas as Na2SO4 (instead ofSo2SO4) and K3PO4 (instead of Po3PO4).

Acknowledgments. The authors gratefully acknowledge

Professor Frank A. J. L. James, head of theRoyal Institution Centre for the History ofScience and Technology, The Royal Institution,21 Albemarle Street, London W1X 4BS, for fur-nishing continued assistance and informationregarding the history of the Royal Institutionand its scientists throughout the “Rediscovery”series.1f For the Cornwall region, Dr. SimonCamm of the Camborne School of Mines,University of Exeter, has been especially helpfuland has served as a guide for the authors asthey researched the tin mines, and the discov-ery of titanium, previously described in TheHEXAGON.1a

References. 1. J. L. and V. R. Marshall, The HEXAGON of Alpha Chi Sigma, (a) 2001, 92(1), 4-5; (b) 2005, 96(1), 4-7; (c) 2007, 98(1), 3-9; (d) 2007, 98(4), 70-76; (e) 2009, 100(4), 72-75; (f)2012, 103(3), 36-41; (g) 2014, 105(2), 24-29;(h) 2014, 105(3), 40-45.

2. J. R. Partington, A History of Chemistry, Vol. 3,1962, Macmillan (London), (a) 33; (b) 69-70;(c) 487-488; (d) 503; (e) 716-721; (f) 782-813.

3. A. L. Lavoisier, Traité Élémentaire de Chimie,1789, Paris, 168.

4. http://www.efloras.org/florataxon.asp, Salsola soda Linnaeus 1753; Salsola kali Linnaeus1753.

5. J. Dalton, A New System of Chemical Philosophy, 1808, Manchester.

6. J. R. Partington, A History of Chemistry, Vol. 4,1962, Macmillan (London), (a) 32-73; (b) 77-96; (c) 99-139; (d) 158-160.

7. R. King, Humphry Davy, 1978, The Royal Institution of Great Britain, London.

8. G. Caroe, The Royal Institution, 1985, John Murray (London).

9. “The Napoleon Prize,” BBC News, 15 March2008,“Napoleon’s medal cast into the sea;”Royal Society of Chemistry, “New LightShed on French Wartime Honour for BritishChemist,” 14 March 1808, http://www.rsc.org/AboutUs/News/PressReleases/2008/ Wartime Honour.asp.

10. F. A. J. L. James, Guides to the Royal Institution of Great Britain: 1 History, 2000,Royal Institution of Great Britain, London.

11. A. Greenberg, A Chemical History Tour, 2000,Wiley-Interscience, (a) 162-163; (b) 193.

12. H. Davy, 1806 Bakerian lecture, “On some chemical agencies of electricity,” published in Phil. Trans., 1807, 97, 1-56.

13. A. Candoré, International Molinology, 1996,No. 53 (November).

Figure 15. Faraday’s statue. 2 Savoy Place, beforethe Institution of Electrical Engineers (N51° 30.58W00° 07.12), on the Victoria Embankment of theThames River (John Henry Foley, sculptor).

Figure 16. The Royal Institution was famous for its lectures popularizing science, and soon evolved into anentertaining educational tool for the public, including the youth. The Christmas lectures were inauguratedby Faraday in 1825. This bronze replica by W. B. Fagan shows Michael Faraday lecturing. In the front rowof the audience, from right to left, are Tyndal, Huxley, Wheatstone, Crookes, Darwin, Daniels, andFrankland.