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Home , Joseph Black

Rediscovery of the Elements Joseph Black-Magnesia and Fixed Air

Firth of , Scotland Forth

City Center

Edinburgh (South Bridge Castle +0"-"New" (and Old) College

National 0 Museum of Mseotfd Black's later Scotland home James L. Marshal, Beta Eta 1971, and Virginia R. Marshall, Beta Eta 2003, 1 l1kmII Department of , University of North Texas, Denton, TX 76203-5070, MODERN UNIVERSITY [email protected] Joseph Black of EDINBURGH Building 9 Joseph Black (1728-1799) (Figure 1) is per- haps best known for the discovery and charac- terization of (fixed air), made Figure 1. (Left) Engraving of Joseph Black, made in during his research with alkalies and carbon- 1800 by (1757-1834), taken from a ates. Simultaneously, he made the first chemi- ca 1790 portraitby (1756-1823). cal distinction between calcia (CaO) and mag- 4 Raeburn was a student of David Martin, whose nesia (MgO) and thus could be credited with portrait of young Joseph Black is shown on the the discovery of . This research was front cover performed at the , Figure 2. Modern map of Edinburgh. The chemical Scotland (Figure 2)." discoveries of Black were performed at the Black is also known for his pioneering Edinburgh "Old College,"whose buildings were research in latent heat at the University of taken down and replaced by the "New College" Glasgow, where he was the first to notice that during 1827-1831. The Royal Museum of the temperature of an -water mixture does Scotland is located 200 meters west, where not rise above the freezing point of water until exhibits on Black are presented (see Figure 8). all of the ice has melted (Figure 3)." The modern campus is 2.7 km south of the "New College." During his last 18 years, Black lived on 2 Joseph Black's career.'bd Joseph Black's family Nicholson Street, a continuation of South Bridge. was of Scottish origin. His father was born in Belfast but migrated to Bordeaux, France, where become professor of anatomy and lecturer in remained at Edinburgh the remainder of his he set up a business. The son Joseph chemistry, replacing Cullen who had taken a life (Figures 4, 5). returned to the British Isles and studied four position at the University of Edinburgh; Black's scientific reputation was widespread years (1746-1750) in Glasgow with became one of the distinguished pro- throughout and America, and he was Cullen (1710-1790). Black then matriculated at fessors at Edinburgh who helped it become visited frequently by those who sought exper- the University of Edinburgh (1750-1754), where one of the leading medical schools in Europe. tise and guidance from the master (Figures 6, he earned his medical degree with Charles Then in 1766 Black returned to the University 7). Smithson Tennant (1761-1815; the discover- Alston (1683-1760), the Chair of Botany and a of Edinburgh as professor of chemistry, replac- er of iridium and osmium') studied with Black specialist of materia medical (medicinal drugs). ing Cullen who had been promoted to in 1781. When the Polish scientist Jedrzej Black then returned to Glasgow in 1756 to Professor of the Institutes of . Black Sniadecki (1768-1838; the discoverer of

40 THE HEXAGON/FALL 2014 been known for millennia." It was believed by Medieval chemistsyb that causticity was induced by a "quantity of pure fire" that had been imparted to the ." By the 1700s a sophisticated theory had been developed by Friedrich Meyer (1705-1765), a German a Johann apothecary in Osnabruck (located between Cologne and Hamburg)." Adopting an idea 7 2 _ 70 from terra pinguis, the "fatty earth" which was and the forerun- 3 CEP H 's' L the principle of combustibility A ner of"phlogiston,"" Meyer invoked an acidum 0!Y LL pinque ("fatty acid"), a fiery principle which sat- urated mild alkalies to produce caustic alkalies. L L+;i 111,L P For example,

Chalk (CaCO3) +"acidum pinque" -+ caustic P 7 lime (CaO, slaked lime) The slippery feeling of a caustic alkali (such as sodium hydroxide, today's lye or "Drano") rr was explained by the saturation with this oily Figure 4. Both Glasgow and Edinburgh claim Joseph substance. Shortly afterward, this principle Black. This is the Joseph Black Building (Chemistry "acidum pinque" was given the more descrip- Building) in Edinburgh (N55 55.44 W03 10.58) tive label of causticum." According . r..: at the present-day south campus, occupied in 1924. to this theory of causticum, one could distinguish a mild alkali (such as sodium Figure 3. TDiN plaque resides on the Joseph Black Building (Chemistry Building) of the modern University carbonate or carbonate) from a caustic of Glasgow (N55 52.32 W04 17.57). Black's main contribution in Glasgow was his work in latent heat Id alkali (such as sodium hydroxide or calcium in 1761. Black preferred to do research in the winter, when ice was available for his and latent hydroxide) by adding acid. In this diagnostic heat studies. His ideas on the latent heat of steam gave the inspiration and technology to devel- test, mild alkalies would effervesce by absorp- op steam power. In his day the campus was on High Street, 3.5 km east of the present campus; the build- tion of causticum, while the caustic alkalies, ings now are completely gone. already saturated with acidum pinque, did not effervesce. This effervescence was understood "vestium,"" traveled to Western Europe to fur- the caustic forms were too acrid to be useful merely to be, in the parlance of the times, a ther his education, he was prevented from vis- medicinal remedies-when caustic alkali was "symptom of the violent movements caused by iting (1743-1794) because of applied to a dog's bladder in an attempt to dis- mutual saturation of acid and alkali."" Today, the French Revolution; as an obvious alterna- solve the stones, instead they "dissolved the this effervescence is known to be generation of tive he turned to Black in Edinburgh. Benjamin 7 bladder." Hence, the mild forms were pre- carbon dioxide and is the standard geologist Rush, a co-signer of the Declaration of scribed for humans, such as ordinary chalk field test for limestone (CaCO3 + acid -+ C0 ). Independence, had earned 2 his medical degree (CaCO 3). It was soon recognized that chalk However, there were gravimetric difficulties at the University of Edinburgh; he returned to might also be a useful remedy for stomach mal- with this idea: when limestone calcined to form Philadelphia in 1769 and presented courses at adies because it relieved indigestion. (Today, the quicklime, it supposedly received causticum the College of Philadelphia (today the antacid CaCO 3 is available as "Tums.") from the fire, but it lost weight. This loss of University of Pennsylvania) based on Joseph weight was known since the ancient Black's very popular lectures. Theory of caustic and mild alkalies. The Romans-but the significance was not recog- technology of heating limestone (mild calcia) to Caustic and mild alkalies as . As a nized because it was considered to be a simple produce mortar (quicklime, caustic calcia) has student at Edinburgh, Joseph Black became "loss of water."' intrigued with alkalies, a research interest of his advisor Charles Alston. In the 1700s, alkalies were known to include the groups of vegetable (potash), marine (soda), volatile (), and calcareous (lime). Each of these alkalies could appear in "mild" (carbonate) and "caustic" (hydroxide) forms.' The compositions of each were unknown, but today we know these as: I _I Alkali Mild form Caustic form Potash K2C0 3 KOH Soda Na2CO 3 NaOH Ammonia (NH4)2CO 3 NH40H or NH 3 Calcia CaCO 3 CaO or Ca(OH)2 Figure 5. A fewz sketches survive of the Old College in Edinburgh. This sketch"" was made in 1789, and is It was believed that alkalies might be sol- "PrincipalRobertson's house" (left) and the"Teviot chambers"(right, used for classrooms and residences). vents for "urinary calculi" (kidney stones), but These can be identified as the southernmost buildings of the Old College Quadrangle (see Figure 6).

FALL 2014/THE HEXAGON 41 towa t 7

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Figure 6. Edgar's 1765 map of the Edinburgh Old College area."The College Quadrangle is the main campus of Old College. The "Physic [Medical] Gardens"grew medicinal herbs for patients in the Roy1aI Infirmary. Black probably performed his magnesia research in the Infirmary.""" College Wynd [wynd = narrow alley] was the main entrance to the campus (see Figure 7). There was no easy access to City Center Figure 7. Black s earlier days were spent in College of Edinburgh; one had to cross Cowgate, essentially a ravine. South Bridge (see Figure 2), the south-north Wynd, a ramshackle district at the north entrance of road linking with central Edinburgh, was built in 1788, passing directly through the Physic Gardens. the Old College. A "wynd" (rhymes with "find")is a narrow alley in Scotland. Nearby was the residence Black's research with carbonates. Black's case."' Why should two independent phenom- of the Scott family (where Sir Walter Scott was born work, presented in his medical dissertation at ena give the same quantitative result? Was in 1771),'" now marked with a plaque mounted the University of Edinburgh," has been there a mysterious air being produced, that was high on a corner building (N55 56.87 W03 described as"a brilliant model, perhaps the first identical, in either calcination or acidification? 11.25). (Drawing by William Channing"'.) successful model, of a quantitative chemical Black then reacted calcium oxide with potas- investigation, as well as a classical exemplar of sium carbonate: "When I precipitated lime by a an experimental science worthy of comparison common alkali (i.e., CaO + K2C0 3 -0 CaCO 3), had been known for several centuries but had with Newton's Opticks."' Black's early notes' there is no effervescence: the air quits the alka- been considered to be merely a variety of chalk from 1751 show that first he had tested the idea li for the lime; but it is lime no more, but CCC (, CaCO 3), even by such that the fire imparted causticum to the chalk [chalk]: it now effervesces, which good lime will sages as George Ernst Stahl (1659-1734), the 7 (Note 1) (CaCO3) to produce the quicklime (CaO). Since not." He concluded lime (CaO) contributes champion of phlogiston.' quicklime becomes mild upon exposure to the nothing to the alkalies; it only removed a pecu- For his dissertation topic, why did Joseph air, then obviously the quicklime was suppos- liar kind of air that prevented their caustic Black choose obscure magnesia rather than edly losing this causticum to the atmosphere. properties from being developed. Black was well-known lime, which would have com- Perhaps, he thought, one could catch this elu- thus visualizing this fiery principle not as some manded more attention? A possible reason'' sive principle in a bottle.2" Black set up an elusive abstraction, but instead as a chemical was that this mild-mannered scientist wanted experiment whereby a dish filled with caustic entity, which could be passed to or from the to avoid contention between his advisor Alston lime (CaO) was allowed to float in water with atmosphere, or which in solution could silently and Robert Whytt (1714-1766), a "bright lumi- an inverted glass vessel over it.2' Hoping this pass between substances, changing their chem- nary in the rising University." Both Alston igneous matter might be collected, instead he ical identities. This was the key observation, and Whytt had performed experiments on the observed that the air space above the quick- according to (1773-1852), medicinal effects of lime-water and had pub- lime, if anything, had been reduced in volume, the Scottish chronicler of early 19th century lished on the subject, but there was a dispute of making him suspicious that something had chemical history: "What a multitude of impor- priority. Whytt, a specialist of the nervous sys- removed from the atmosphere. The fact that the tant consequences naturally flowed from this tem (he discovered the unconscious reflex reac- 7 quicklime had simultaneously increased in discovery!" (Figure 8). tion'a), was promoting his own "discovery,"oys- weight while converting to the mild form sup- ter-shell lime. Alston criticized Whytt's experi- ported this idea. Chalk and magnesia. Joseph Black then mental methods and believed Whytt's oyster Then Black measured the loss of weight of became interested in magnesia alba (Figure 9), shells were no better than ordinary limestone.' chalk when it was either calcined or treated then sold in Rome as a stomach remedy. Black sidestepped the issue by concentrating on with acid, and found it to be the same in either Magnesia alba (magnesium carbonate, MgCO 3 ) a different medicant.

42 THE HEXAGON/FALL 2014 I LI I ILA _ I' ,l r 1i"jJ

Figure 8. In the Royal Museum of Scotland on Chambers Street (N55 56.81 W03 11.44), datingfrom 1851, is found this exhibit of Joseph Black, consisting of laboratory glassware, utensils, and bottles. The l-*44~- bottle in the lower left was used by Black to collect carbonic acid."" Another Scottish scientist featured in the museum is (1766-1844), who fully characterized strontium."

f figure 9. This 0.44 kg literally poured, in the open atmosphere, from a pecimen of magnesite glass vessel onto a candle to extinguish it. magnesium carbonate) is By a series of experiments he showed that:' om Magnesia, Thessaly, magnesia alba (MgCO3) + heat -+ calcined Greece, and is the magnesia (MgO) + fixed air (CO2) ytimnological source for magnesia alba (MgCO3) + acid (HCl) - magnesia alba (white magnesia salt (MgCl2) + fixed air (CO2 ) uzgnesia).s Another calcined magnesia (MgO) + acid (HCl) - the mineral from the locality, same magnesia salt (MgCl2) magnesia nigra (black Black repeated these experiments with lime, nagnesia), pyrolusite and then continued on with the other three manganese dioxide) is the alkalies-vegetable, marine, and volatile-and tymological origin of the showed that in each case each mild form was lenient manganese. simply the caustic form plus fixed air. He devel- I'hoto, elemental oped a general schedule of reactions that collection of the authors. applied consistently for all groups. For example, he showed that reaction of "mild ammonia" with slaked (caustic) lime gives smelly (caustic) There was also disagreement between He separated the MgCO , dried it, and 3 ammonia and chalk precipitate: Alston and Whytt regarding the genesis of weighed it. Then he calcined the MgCO to 3 Mild ammonia ((NH ) CO ) + caustic lime causticity. Whytt ardently maintained that produce magnesia (MgO), resulting in a loss of 4 2 3 (CaO) - caustic ammonia (NH ) + chalk indeed there was a "fiery substance" in caustic 7/12 of its weight. He surmised the loss of 3 (CaCO ) lime, while Alston favored some sort of chemi- weight was due to the expulsion of the same 3 (solution) + (solution) -+ (smelly solution!) cal rearrangement. Black thought it would be mysterious air, which he was able to collect and + (milky precipitate) "presumptuous to settle the quarrel between study. He demonstrated that this air, when them"'--but ironically, his research with mag- bubbled into a solution of quicklime (CaO), Black's full characterizations with magne- nesia did just that. precipitated a milky precipitate, identified as sium and calcium salts showed the two were the air could be "fixed," Black's experiments. For his experiments chalk (CaCO 3). Thus, definitely different. Thus, Black was the first to i.e., rendered nonvolatile. (This chemical proce- and (Figure 10), Black carefully prepared pure mag- establish magnesium as a separate entity, dure exists to this day as the classical laborato- not just a variation of the calcareous earth."' nesia alba (MgCO 3) from Epsom salt (Figure 11) test for carbon dioxide.) In subsequent class and pearl ashes, ry (Note 2). demonstrations, he fascinated his audiences by Black's research further clarified the nature MgSO 4 (Epsom salt) + K2 CO3 (pearl ashes) showing how the invisible "fixed air" could be of the alkaline earth medicants. Previously, MgCO 3 (magnesia alba) + K2C0 3 .

FALL 2014/THE HEXAGON 43 ii*itii'II I U F~ii 1 ii'. _ 7

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Figure 10. This is the Royal Infirmary, where Black probably performed his carbonate studies for his M.S. dissertation. The Royal Infirmary was the foundation of the Medical Institute at Edinburgh because it allowed medical studies with patients, as well as provided teaching and research facilities. It was built in 1741 and demolished in 1884. (Engravingby Paul Sandby.21)

"magnesia alba" or "magnesia" could each refer called him "l'illustre Black, le chef et le Nestor to either magnesium oxide (MgO) or magne- de cette grande revolution chimique" ("the sium carbonate (MgCO 3). Likewise, "lime" illustrious Black, the chief and the Nestor of the could mean "quicklime" (CaO) or chalk grand chemical revolution").4 (CaCO3). No doubt many pharmacological for- mulations of the 1700s were mixtures. Black's laboratory. Where did Joseph Black However, after Black's defining research, the perform his chemical experiments? This is not .A descriptions in the pharmacopoeias became known for certain. There are two unambiguous: CaO was "calcined calx" or"calx possibilities7"" (see Figure 6): the Medical usta," MgO was "calcined magnesia" or "mag- Institute laboratories ("Scott's and "Partner's") nesia usta" ("usta" is an old Latin word mean- by the Physic Gardens, set up in 1724 to pre- ing "cremated"); and the mild calcareous alka- pare medicines,'7 or the Infirmary where some lies were "carbonas calcis" (CaCO 3) and "car- lectures were held (Figure 10). The more prob- bonas magnesiae" (MgCO3)." Even today, able choice- is the Infirmary, because Black "magnesia usta" is occasionally used to might not have been given access by the oper- describe commercial MgO products. ators of the Physic Garden laboratories, owing Figure 11. Epsom Wells is marked by this monu- to envy and internal rivalry.""',1 (Because of his ment in the center of a spiral road in Well Way 0 Preamble to Lavoisier. A clear parallel exists successes and reputation, Joseph Black-a (N51" 19.63 Wo 17.41), located 25 km south- between the works of Joseph Black and Antoine fresh M.D. graduate-had actually been pro- west of London. Epsom Wells, a source of the Lavoisier.b Lavoisier considered combustion to posed as a temporary Chair of Chemistry before eponymous salts (magnesium sulfate), was a fash- be the addition of a "principe oxigene,"" a real Cullen returned to Edinburgh in 1766!"''") ionable spa in the 1600s and 1700s, known for the substance, as opposed to Stahl's of loss of healthy benefits of its waters (mostly to prevent chimeric phlogistron; Black construed calcining The nature of "fixed air." Black realized that constipation). In 1851 the well was closed owing as the loss of a gas, instead of the gain of a"fire air was a distinct species "dispersed thro' the to pollution. The building in the background is a principle." In both cases, as acclaimed by atmosphere"'" and probably was the same aer nursing home. Antoine Francois Fourcroy (1755-1809), malignus (malignant air) that had often been Lavoisier's colleague and advocate, we need mentioned under the name of choke-damp, gas (Mark Twain in Innocents Abroad reported that not invoke a "principe imaginaire" ("imaginary sylvestre, spiritus sylvestre, mephitic air, and he wanted to try the experiment at Grotta del principle"); instead, we have an "8tre rdel" ("real gas carbonum, among others. He thought this Cane but complained that he "had no dog.")" one")!'' gas was the same as that in the bubbly spas at Black also recognized this gas was the same as In all of these studies, Black depended upon Pyrmont in Germany"' and in caves such as that produced by or the burning precise gravimetric analysis, perhaps the first to Grotta del Cane"" (Cave of the Dog) near of charcoal. employ the balance totally "in almost every Naples, Italy (N40 49.62 E14 10.32). In Grotta Black intended to pursue the"serious study" stage"of his chemical investigations." Fourcroy del Cane, a meter blanket of a noxious gas (car- of "fixed air and similar elastic fluids."" recognized Black's importance to Lavoisier's bon dioxide) lay low in the cave, harmless to a However, a "load of new official duties was laid New Chemistry three decades later; Fourcroy human being but deadly to a canine at his feet. upon [him]"" and he never resumed this

44 THE HEXAGON/FALL 2014 research. Later, Antoine Lavoisier would estab- lish the chemical composition of carbon dioxide (1774),' but in the meantime Joseph Black sus- pected there might be more to "mephitic air" than simply "fixed air." Shortly after returning to Edinburgh in 1766, he assigned the task of a more comprehensive study of mephitic air to (1749-1819), son of John Rutherford (1695-1779), one of the original founders of the Medical Institute at Edinburgh. Daniel completed his work 17 years after Black's original dissertation; he reported his results in his own dissertation of 1772. In the next issue of The HEXAGON, we will see that Daniel discovered a new element in this gas - nitrogen. 0 Notes 1. Andreas Sigismund Marggraf (1709- 1782),' apparently unaware of Black's work, also distinguished magnesia from lime four years later.' 2. A preliminary chemical distinction between magnesia and calcia had been made in 1722 by Friedrich Hoffmann"' (1660-1742), the first chair of medicine at Halle, the same uni- versity as Stahl's." A difference was observed in solubility and taste of the sulfates (calcium insoluble, tasteless; magnesium soluble, bitter). Acknowledgments Dr. Robert G. W. Anderson, Emeritus Fellow, Clare Hall, Cambridge University, and Dr. Peter J. T. Morris, Keeper of Research Projects, Research and Public History Department, Science Museum, London, are gratefully 7. T. Thomson, , 1830, H. 14. A. F. Fourcroy, Systeme des Connai1CI acknowledged for furnishing important infor- Colburn and R. Bentley, Vol. 1, 317. Chimiques, et leur Applications aux mation regarding the laboratories and resi- 8. P. Enghag, Encyclopedia of the Elements, Phnomenes de la Nature et de l'Art, 18oo dences of Joseph Black. 2004, Wiley-VCH, 1999, Industrilitteratur, (Brumaire, An IX), Paris, (a) 29; (b) 49. References. Stockholm, (a) 324; (b) 328. 15. R. G. W. Anderson, The Playfair CollectiOI 9. J. R. Partington, A History of Chemistry, and the Teaching of Chemistry at the University1 1. J. R. Partington, A History of Chemistry, 1962, 1962, Vol. II, Macmillan, N.Y., (a) 229; (b) of Edinburgh 1713-1858, 1978, Royal Scottish Vol. III, Macmillan, N.Y., (a) 93; (b) 130-143; 605; (c) 648; (d) 695; (e) 728. Museum Studies, (a) 6; (b) 19-34; (c) 71-73; (c) 145-146; (d) 153-156; (e) 423. (d) 133. 10. C. Brown, Nature, 1878, 18(456), 346-347. 2. H. Guerlac, Isis, 1957, (a) 48(2), 124-151; (b) 16. R.G.W. Anderson, personal communica tion. 48(4), 433-456. 11. Dissertation: J. Black, Humore Acido a Cibo Orto et Magnesia Alba, [The acid humor 17. A. G. Fraser, The Building of Old Collegc. 3 J. L. and V. R. Marshall, The HEXAGON of arising from food and magnesia alba],1754, Adam, Playfair &and University of Edinburgh, Alpha Chi Sigma, (a) 2002, 93(3), 42-47; (b) Edinburgh [translation and comments: L. 1989, Edinburgh University Press, 27-50. 2005, 96(1), 4-7; (c) 2006, 97(2), 24-29; (d) Dobbin, J. Chem. Educ., 1935, 12(5), 225-228 18. W. Ramsay, The Gases of 2008, 99(3), 42-46; (e) 2009, 100(l), 8-13; (f) the Atmosphere, and 12(6), 268-273];"Experiments upon 1915, Macmillan, 2011, 102(2), 20-24. 41. magnesia alba, Quicklime, and some other 19. M. Twain, Innocents Abroad, 1869, American 4. B. Railiend, Andrius Sniadeckis, [in Alcaline Substances," Essays and Observations, Publishing Co., 322. Lithuanian], 2005, Vilniaus universiteto 1756, Vol. 2, Edinburgh, 157-225. leidykla [Vilnius University Publishing 20. National Library of Scotland, Edgar's 1765 12. A. Grant, The Story of the University of House], Vilnius, Lithuania, 49; 267-268. revision, http://maps.nls.uk/view/74400010 Edinburgh during its First Three Hundred 5. A. Greenberg, A Chemical History Tour, 2000, Years, 1884, (a) Vols I and (b) II, London, 21. J. Grant, Cassell's Old and New Edinburgh, Wiley-Interscience, 134. Longmans, Green, and Co. Vol. 2, Cassell, Petter, Galpin & Co., 1882, (a) 6. A. Greenberg, From Alchemy to Chemistry in 13.T. L. Hankins, Science and the Enlightenment, 254-256; (b) 300. Picture and Story, Wiley-Interscience, 267. 1985, Cambridge University Press, 90.

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