Rediscovery of the Elements

Daniel Rutherford, Nitrogen,and the Demise of Phlogiston

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James L. Marshall, Beta Eta /971, andVirginia R. Marshall, Beta Eta 2003,Department of Chemistry, University ofNorth Texas, Denton, TX 76203-5070,jimm@unt.edu

In the previous HEXAGON "Rediscovery"article, the life and work of Joseph Black(1728-1799) was introduced." As a graduate

student at the University of Edinburgh,Scotland, Black discovered fixed air (carbondioxide) and characterized magnesium as asubstance separate from calcium, and thus maybe considered the discoverer of that calcareouselement. Afterwards he became professor atthe University of Glasgow, where he developedthe concept of latent heat. He returned to theUniversity of Edinburgh in 1766 as the head ofchemistry. (Figure 1).

Black as a professor at Edinburgh. Upon hisreturn to Edinburgh (Figure 2), Black turnedaway from fundamental research and instead

concentrated on industry and teaching. Anactive participant in the Scottish Enlighten-ment, he was sought out by scientists through-out Europe for guidance in chemical curriculaand industrial research.2" He mentored severalgraduate students, one of whom succeededhim as chair of chemistry,' Thomas CharlesHope (1766-1844), who first fully characterizedstrontium, discovered in a mine in northwest

Modern BotanicGardens "

Edinburgh, ScotlandFirth ofForthOriginal

Leith Walk(Botanic

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Rutherford'sEdinburgh 0 " home

Castle "".-'New" College

National " South BridgeMuseum of

Scotland Black's finalhome

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UNIV of EDINBURGHJoseph Black

Building Daniel Rutherford% Building

Figure 2. Map of Edinburgh, Scotland. The chemical discoucrics of Black and Rutherford were performed atthe "Old College"in Edinburgh, which is not identified on this modern map, because it was demolished andreplaced by buildings of the "New College,"on South Bridge (N55 56.85 W03 11.17). Rutherford, later aprofessor of botany at the University of Edinburgh, maintained the Botanic Gardens at"Leith Walk"(see Figures 4,5); today's Royal Gardens are located 2 km west. The locations of the homes of Black andRutherford are known, but they no longer exist. The modern campus is 2.7 km south of the "New Campus."

Scotland." Other students of Black attainedprominent positions at Oxford University."'Another of his students was Daniel Rutherford(1749-1819), (Figure 3) who was the son ofJohn Rutherford (1695-1779), one of thefounders of the Medical Institute atEdinburgh.'; Daniel later became professor ofbotany at the University of Edinburgh (Figures4-6), but never rose to the prominence of hisfather John or of Joseph Black. However, whilea student of Black, he found his mark as thediscoverer of "malignant air," later to be knownas nitrogen.

The characterization of "malignant air."Daniel Rutherford described the discovery ofthis new air in his 1772 M.D. dissertation("Inaugural dissertation on the air called fixedor mephitic").' In his dissertation research,Rutherford "destroyed" ordinary air (i.e.,removed the oxygen) by burning charcoal, can-dle, or phosphorus, or by respiration with a liv-ing mouse. In the cases where mephitic air(fixed air, or carbon dioxide) was produced, heremoved this with alkali, following the proce-dure of his mentor Joseph Black.', Rutherfordconcluded that the remaining "malignant air"3

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I une . Ioseph Blais origItal paintinfronmwhich most black and white engravings arereproduced. It was painted (ca. 1790) by Sir HenryRaeburn, titled "Professor Joseph Black(1728-1799)."Courtesy, Hunterian Museum andArt Gallerv, Un ier.it' o Glaot.

Figure 3. Lngra'ing of Lamel Ruthe rti, atter apainting by Sir Henry Raeburn, from ref o.

must be "atmospheric air saturated with phlo-giston" since it "cannot be converted intomephitic air by combustion."3 Rutherford nevergave his air a specific name, but did speculatethat it was "pure phlogiston united to commonair" seeming to "form another species of air"[authors' italics].

Rutherford was impressed with the "poiso-nous" nature of mephitic air, which lay low incaverns and asphyxiated small animals on thecave floor.' He was puzzled by malignant air,because when "all mephitic air had beenremoved by caustic lixivium [alkali], whatremains does not become in any way morewholesome."' In another experiment,Rutherford noted that air "which has beenblown through ignited coals, and then purified

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figure 4. This is a north view of the Leith Walk Gardens at the time of Rutherford, who maintained themwhen he became professor of botany in 1786 at the University of Edinburgh." The road in the foreground(left-right) is Leith Walk, which exists today (see map, Figure 2). The field to the right has rows of rhubarb,grown for medicinal purposes; the seeds were obtained from St. Petersburg, Russia. Only a tiny remnant ofthe original garden exists todayl (see next figure). Courtesy, Royal Botanic Garden, Edinburgh, Scotland.

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I i''1 1 . inn k ht toal)y: I lopetotm riscent, an arc extending from Leith Walk (road) oJ a gras y-w ogof trees with benches for resting (N55 57.69 W03 11.05). Inset: Sign on fence.

from all mephitic air, is nevertheless still foundto be malignant and quite similar to that whichis spoiled by respiration."' Hearing of Priestley'sexperiments, where plants became invigorated(and not "poisoned") by fixed air,' Rutherfordrealized that the "malignancy" induced by res-piration, combustion, or calcining was a sepa-rate phenomenon from the"mephitic"nature offixed air. Unfortunately, Rutherford never

resolved the issue of "mephitic air" vs. "malig-nant"air.

It is not known where Daniel Rutherfordconducted his research."' Quite possibly it wasin one of the buildings on the north side of thePhysic Gardens (see map of previous HEXA-

GON publication') which included the originallaboratories set up by John Rutherford's med-ical group." These buildings were later used by

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Figure 6. The Rutherford Building in the modern Uniersity of Limb rgh (N5-)' 55.33 103) 7025) isnamed after Daniel Rutherford, professor of botany and keeper of the Royal Gardens at Edinburgh.Rutherford is also known for inventing the maximum-minimum thermometer; he was also the uncle ofSir Walter Scott (1771-1832).

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Figure 7. The cornerstone of the New College was laid on November 16, 1789, by George III. The view isnorthward on North Bridge. The observer's viewpoint is close to the original location of John Rutherford'sMedical buildings on the north side of the Physic Gardens, i.e., where the son Daniel Rutherford probablyperformed his research on "malignant air." See the next figure for the modern appearance of this site.(Drawing 1789, David Allan.)

Joseph Black (starting in 1766) for his teachingand laboratory procedures, before he movedinto the new chemistry building which wasconstructed in the Old University Quadrangle

in 1781. This building was the one where Hopeperformed his research on strontium,"" andwas removed during the later construction ofthe New Campus at the same site (Figures 7,8).

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Cavendish's parallel research. WilliamRamsay, the discoverer of the inert gases,"believed that since Rutherford recognized that"malignant air" was a new substance, he "maywell be credited" with the discovery of nitro-gen." However, Henry Cavendish (1731-1810;the discoverer of hydrogen)" performed somework which anticipated Rutherford's research.Six months before Rutherford's thesis was pub-lished, Joseph Priestley (1733-1804)' read apaper to the Royal Society relaying privateinformation furnished by Cavendish. In hisresearch, Cavendish gave a more quantitative,but less general, description of Rutherford'sgas. Cavendish passed ordinary air through ared-hot tube of charcoal, with subsequentremoval of fixed air by caustic alkali. Cavendishrepeated this procedure repeatedly, until nomore diminution of the air was observed. Thus,he observed a reduction of 180 to 162 ounces,"and he noticed that the density "differed littlefrom ordinary air, perhaps somewhat lighter."'It is not clear what interpretation he gave ofthese observations, but it appears that he, likeRutherford, considered the residual gas to bethe consequence of the "destruction of com-mon air." His work was never formally pub-lished, and he has not been generally viewed asa co-discoverer of the gas. (Cavendish later iso-lated a small quantity of inert gaseous residuefrom nitrogen by sparking, but he did notunderstand it was a new separate substance,later recognized as a new element-argon-byRamsay and Raleigh.")

Scheele's discovery of "spoiled air." CarlWilhelm Scheele (1742-1786)' may be consid-ered to be a co-discoverer of nitrogen. Hedescribed two kinds of air, viz., "spoiled air" and"fire air" (German "verdorbene Luft" and"Feuerluft" or Swedish "skamd luft" and "eldsluft," respectively.)"' His work was performed atthe same time as Rutherford's, but it was notpublished until five years later.' (Similarly, oxy-gen was discovered by Scheele before Priestley,but the opportunistic Priestley published first.1b,,)

Scheele's understanding of nitrogen wasadvanced beyond that of Rutherford. Instead ofviewing the gas to be the product of somevague "destruction" of air, Scheele believed that"air must be composed of two different kinds ofelastic fluids."' If he had published promptly,there is no doubt he would be considered thediscoverer of nitrogen. In fact, in the GermanWikipedia, Scheele is considered the lone dis-coverer of nitrogen; Rutherford is not men-tioned.'"

What should the new gas be called? AfterRutherford's announcement' of 1772, the des-ignation "phlogisticated air" or "malignant air"

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Old College where Black and Rutherford worked, but is now actually the "Old College,"because of theNew Campus further south. It presently houses the library complex of the university (Playfair Library Hall).

was commonly used for the portion of theatmosphere remaining after ordinary air hadbeen "destroyed" by combustion and fixed airhad been removed." But it was not clearwhether (a) the diminution of the atmosphereduring combustion was a fundamental trans-formation of air, a "consequence of the atmos-phere becoming overcharged with phlogis-ton,"" or perhaps, (b) as Scheele suggested, theatmosphere was composed of two distinct partsthat were separable. During the next twodecades, various names were proposed for the"phlogisticated air," including:

(a) "mofette"-the gas escaping from avolcanic vent-used earlier by Lavoisier; 4

(b) "azote"-"without life"-proposed byGuyton de Morveau, 1737-1816, whointroduced the New Chemical Nomenclature(Methode de Nomenclature Chimique);"'

(c) "azotic gas"-used by Cavendish;"

(d) "nitrogene"or"nitrogen"-"niter genera-tor," created by sparking the atmosphere-proposed in 1790 by Jean-Antoine Chaptal(1756-1832)," a French industrialist andpopular author of science texts; and GeorgePearson (1751-1828), a student of JosephBlack who translated Mithode de Nomen-clature Chimique" into English" in 1794.

In Lavoisier's 1789 Trait,'2 nitrogen was rec-ognized as an element for the first time; he list-ed it as "azote." The French chemical literaturehas retained "azote"; but with Pearson's trans-lation of Nomenclature Chimique, "nitrogen"passed into the English vocabulary. The

Germans use "Stickstoff" ("suffocating sub-stance") and the Swedes "kvyve" ("asphyxiate")since the 1790s. The Russians transliterated theFrench name and call the substance "a3OT."

Just what exactly is this new gas? Lavoisier'sidentification of azote as an element" did notimmediately settle the issue of exactly what thissubstance was. William Higgins (1763-1825),an Irish chemist who in 1784 was one of theearliest antiphlogistonists and an early advo-cate of the atomic theory, proposed that theatmosphere was indeed a mixture of gases, butwas unclear whether oxygen and nitrogen inthe atmosphere were separate substances orwere combined." John Dalton (1766-1844) pro-posed a clearer description of the atmosphere,"which he declared consisted of discrete parti-cles."' In 1803 he hypothesized' that each ele-ment consisted of atoms of a specific weight,and he gave each element its own specialsymbol (e.g., 0 for oxygen, (D for nitrogen)."Dalton was formalizing these ideas on theatmosphere and its constituent elements dur-ing Priestley's twilight years as Priestley contin-ued to preach that phlogisiticated air (nitrogen)was an undefinable substance containingdephlogisticated air (oxygen), possibly even acompound of dephlogisticated air and inflam-mable air (hydrogen)." But Priestley was nowvirtually alone with his antiquated philosophy,and when he died (1804) there were noremaining significant adherents to the philoso-phy of phlogiston." Nitrogen had joined theranks of the true elements and was included as

an authentic member of the elements inDalton's grand philosophy of 1808.4

But the story is not yet finished. A majorsource of confusion was the large inventory ofnitrogen oxides that had been described princi-

pally by Priestley and Cavendish. Jons JakobBerzelius (1779-1848), the Swedish chemicalgiant who seemed to be at the "center of nearlyevery significant scientific discovery in chem-

istry," 5 thought nitrogen was a compound of

oxygen with an"ammonium"radical, analogousto his idea that chlorine was a compound of

oxygen with a muriatic radical." However, by1823 Berzelius had accepted chlorine" andnitrogen as bona fide elements." But it was notuntil the final acceptance of Avogadro's

hypothesis and the application of Gay-Lussac'sLaw of Combining Volumes, when StanislaoCannizzaro (1826-1910) prepared his famous

pamphlet of 1858,'' that the true nature ofatmospheric nitrogen was understood. This

pamphlet-which was distributed to membersof the Karlsruhe Chemical Congress of 1960and which inspired a German and a Russian

(Lothar Meyer and Dmitri Mendeleev) to for-mulate the Periodic Table several years later '-finally established the true nature of atmos-pheric nitrogen: a diatomic element, N2.

The legacy of Joseph Black. The scientificthinking of Joseph Black was so advanced thatoften he is regarded as one of the first in GreatBritain to accept Lavoisier's New Chemistry."James R. Partington (1886-1965), the author ofthe comprehensive A History of Chemistry,implies" that Black was endorsing Lavoisier'sviews in Edinburgh even before 1784. However,a closer study of Black's life shows a more con-servative approach. It was actually one of hisstudents, Richard Lubbock (1759-1808)," whofirst vigorously advocated Lavoisier's ideas.Lubbock called the vital portion of the atmos-

phere principium sorbile (absorbable principle;called by Lavoisier principe oxigene) and hedevoted his entire Dissertation in Edinburgh(1784) to this subject.' (After graduationLubbock became a practicing physician inNorwich, in Norfolk County, England). The firstprofessor in Scotland to advocate exclusivelyLavoisier's chemistry9 actually was Black's stu-

dent, Thomas Charles Hope, who became pro-fessor at Glasgow in 1787, later at Edinburgh.

The cautious Black believed there were toomany unanswered questions-with a "schemeso dependent upon a few key experiments..."he was worried that "should these experimentsbe overturned the entire structure was under-mined."" With the backdrop of the ScottishEnlightenment, the role of Black was to createthe cultural environment at Edinburgh whichallowed free debate, tolerating all views.

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Student societies flourished that nurtured thisintellectual freedom, giving rise to "one of theearliest sustained debates over the new chem-istry outside Paris."" The conversion of Blackwas gradual. In the end, he was convinced notby the students' youthful exuberance which hefostered, but ultimately by the wealth of theirdata and cogent arguments. In 1790 he finallyproclaimed his endorsement of the NewChemistry in a letter to Lavoisier," which waspublished in the French journal Annales deChimie."

Acknowledgments.The assistance of Robert G. W. Anderson,

Emeritus Fellow, Clare Hall, CambridgeUniversity, and author of refs 2 and 4b, is grate-fully acknowledged.

References.1. James L. Marshall and Virginia R. Marshall,

The HEXAGON of Alpha Chi Sigma, (a) 2002,93(3), 42-47; (b) 2005, 96(1), 8-13; (c) 2005,96(2), 28-33; (d) 2007, 98(1), 3-9; (e) 2007,98(4), 70-76; (f) 2012, 103(3), 36-41; (g)2014, 105(3), 40-45.

2. R. G. W. Anderson, The Correspondence ofJoseph Black,Vol.1, 2012, Ashgate Publishers,(a) 36-38; (b) 40.

3. Dissertation Inauguralis de are fixo, aut mephitico("Inaugural dissertation on the air calledfixed or mephitic"), University of Edinburgh,1772. A translation of Rutherford's disserta-tion from the original Latin appears inL. Dobbin, J. Chem. Ed., 1935, 12(8), 370-375.

4. R. G. W. Anderson, (a) private communica-tion; (b) The Playfair Collection and theTeaching of Chemistry at the University ofEdinburgh 1713-1858, 1978, Royal ScottishMuseum Studies, 20-23.

5. A. G. Fraser, The Building of Old College.Adam, Playfair & University of Edinburgh,1989, Edinburgh University Press, 27-50.

6. W. Ramsay, The Gases of the Atmosphere,1915, Macmillan, 41.

7.

8.

J. Priestley, Phil. Trans., 1772, 62, 147-256.

J. R. Partington, A History of Chemistry,Vol. III, 1962, Macmillan, (a) 222; (b) 263;(c) 318; (d) 416-424; (e) 481; (f) 489; (g) 50;(h) 627; (i) 694; (j) 738; (k) 755-822.

9. C. W. Scheele, Chemische Abhandlung conder Luft und dem Feuer ("Chemical Treatiseof Air and Fire"), 1777, Upsala und Leipzig,Verlegt von Magn. Swederus, Buchhindler.

10. http://de.wikipedia.org/wiki/Stickstoff

11. T. Thomson, History of Chemistry, 1830,H. Colburn and R. Bentley, Vol. 1, 346.

12. A.-L. Lavoisier, Tmitc EIrnentaire de Chimie,

1789, Paris.

13. R. E. Schofield, The Enlightened JosephPriestley. A Study of His Life and Work from1773 to 1804, 2004, Pennsylvania StateUniversity Press, University Park, PA,361-365.

14. John Dalton, A New System of ChemicalPhilosophy, 1808, Manchester.

15. P. B. Moore, The Mineralogical Record, 1988,19, 293-295.

16. J. R. Partington, A History of Cheniistr,Vol. IV, Macmillan, 1962, 156-166.

17. S. Cannizzaro, Nuovo Cimento, 1858, 7,321-366.

18. A. Grant, The Story of the University ofEdinburgh during its First Three HundredYears,Vol. 2, 1884, Cambridge UniversityPress.

19. C. E. Perrin, Ambix, 1982, 29(3), 141-195.

20. Letter of Black to Lavoisier, Ann. chim.,1791, 8, 225-229.

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