How to use this course
Friedrich Wöhler is remembered for one reaction, the conversion of ammonium cyanate into urea in 1828, and for a legend attached to it: that he single-handedly refuted the idea that organic substances need a vital force. The reaction was important; the legend is mostly later invention. His real achievement is broader. He was the first to isolate aluminium, beryllium and yttrium as metals, a co-discoverer of isomerism and of compound radicals with Justus von Liebig, the discoverer of silane and of the route from calcium carbide to acetylene, and for 46 years the head of one of Europe’s busiest teaching laboratories.
- General chemistry: stoichiometry, gas laws, oxidation states, enthalpies of formation.
- First-year organic chemistry: functional groups, constitutional isomers.
- For Lesson 05, second-order rate laws; for Lesson 08, the Nernst equation.
Each technical lesson opens with a paragraph for the general reader, then gives precise statements, worked chemistry and exercises with folded solutions. Formulas are written in modern notation; Wöhler used Berzelius’s older atomic weights, and some of his published formulas are doubled or halved compared with ours. The companion module on Liebig treats isomerism, radicals and the Giessen school from the other side.
Timeline
| 1800 | Born 31 July in Eschersheim near Frankfurt am Main, son of August Anton Wöhler and Anna Catharina Schröder. |
| 1814–20 | Gymnasium in Frankfurt; experiments at home and collects minerals. |
| 1820 | Begins studying medicine at Marburg. |
| 1821–23 | Heidelberg; studies chemistry with Leopold Gmelin. |
| 1823 | 2 September: doctorate in medicine, surgery and obstetrics at Heidelberg. Goes to Stockholm to work with Berzelius. |
| 1824 | Prepares oxalic acid by hydrolysis of cyanogen; analysis of silver cyanate meets Liebig’s analysis of silver fulminate. Returns to Frankfurt in October. |
| 1825 | March: begins teaching chemistry at the Gewerbeschule (trade school) in Berlin. |
| 1827 | Isolates aluminium by reducing aluminium chloride with potassium. |
| 1828 | 22 February: reports to Berzelius the synthesis of urea. Isolates beryllium and yttrium. Receives the title of professor. |
| 1831 | Shows that Sefström’s vanadium is del Río’s element (erythronium). Moves to the Höhere Gewerbeschule in Kassel. |
| 1832 | Death of his first wife, Franziska. Works in Liebig’s laboratory at Giessen: the benzoyl radical. |
| 1834 | Marries Julie Pfeiffer. |
| 1836 | Succeeds Friedrich Stromeyer as professor of chemistry and pharmacy at Göttingen. |
| 1837–38 | With Liebig: decomposition of amygdalin; the memoir on uric acid. |
| 1840 | Grundriss der organischen Chemie; the “S. C. H. Windler” satire on substitution. |
| 1844 | Names hydroquinone; studies quinone and quinhydrone. |
| 1845 | Obtains aluminium as small fused pieces and describes its properties. |
| 1850 | Shows that “metallic titanium” crystals from blast furnaces contain carbon and nitrogen. |
| 1854 | Foreign Member of the Royal Society of London. |
| 1856–57 | With Henri Sainte-Claire Deville, crystalline boron and silicon; with Heinrich Buff, silane. |
| 1862 | Prepares calcium carbide and shows that water converts it to acetylene. |
| 1864 | Prussian Pour le Mérite for Sciences and Arts; foreign associate of the Paris Académie des sciences. |
| 1872 | Copley Medal of the Royal Society. |
| 1880 | Cothenius Medal of the Leopoldina. |
| 1882 | Dies in Göttingen on 23 September, aged 82. |
Eschersheim and Frankfurt, 1800–1820
Friedrich Wöhler was born on 31 July 1800 in Eschersheim, a village now inside Frankfurt am Main, then in the Landgraviate of Hesse-Kassel. His father, August Anton Wöhler, had served as master of the horse to the Hessian court and trained as a veterinarian; he later farmed an estate near Frankfurt and became a prominent citizen of the city. His mother, Anna Catharina Schröder, was the daughter of a professor at the gymnasium in Hanau.
The boy was taught at home and in local schools, with extra lessons in Latin, French and music, and entered the Frankfurt gymnasium in 1814. He was a mediocre pupil in the classical curriculum and an eager one outside it. He collected minerals and carried out chemical experiments in a home laboratory his father provided, teaching himself much of the chemistry of the day from books. The habits of a mineral collector, close observation and careful identification, stayed with him throughout his career.
Marburg, Heidelberg, Stockholm, 1820–1824
In 1820 Wöhler began studying medicine at Marburg, and a year later moved to Heidelberg. Medicine was the usual route to a scientific career, but chemistry absorbed him. At Heidelberg he attended Leopold Gmelin’s lectures and worked in Gmelin’s laboratory on cyanic acid and its salts, a subject that would occupy him for years. He qualified as a doctor of medicine, surgery and obstetrics on 2 September 1823.
Gmelin advised him to give up medicine and arranged for him to spend a year with Berzelius in Stockholm, the most sought-after apprenticeship in chemistry. Wöhler worked there from late 1823 into 1824. He learned Berzelius’s methods of mineral analysis, his care with reagents and his notation, and continued the cyanogen work. He also began a friendship with Berzelius that lasted until the Swede’s death in 1848. For more than twenty years Wöhler translated Berzelius’s textbook and annual reports into German, the main channel through which German chemists read him. He returned to Frankfurt in October 1824.
The Stockholm year produced the analysis of silver cyanate that collided with Liebig’s analysis of silver fulminate (Lesson 04). Liebig suspected Wöhler’s numbers; both men rechecked and found them right. The exchange brought them into contact in 1824–25 and soon into a friendship that lasted nearly fifty years.
Berlin and Kassel, 1825–1836
In March 1825 Wöhler began teaching chemistry at the new Gewerbeschule in Berlin, a trade school for future industrialists and technicians. It was not a university post, but it gave him a laboratory and a place in the Berlin scientific community. The six Berlin years were among his most productive. He isolated aluminium in 1827 and beryllium and yttrium in 1828, and in February 1828 he wrote to Berzelius that he had made urea without the use of kidneys. In August 1828 the Prussian king granted him the title of professor.
He married his cousin Franziska Wöhler; they had a son and a daughter. In 1831 he moved to the newly founded higher trade school in Kassel, where he set up a laboratory and took part in founding a nickel works. Franziska died in 1832. That year Wöhler spent several weeks in Liebig’s laboratory at Giessen, the only extended period in which the two worked side by side, and the result was the paper on the benzoyl radical, their most famous joint work. In 1834 Wöhler married Julie Pfeiffer, daughter of a Kassel banker; they had four daughters.
In 1836 Friedrich Stromeyer, professor of chemistry at Göttingen, died, and Wöhler was appointed his successor as ordinary professor of chemistry and pharmacy. He stayed for the rest of his life.
Cyanogen, cyanates and oxalic acid
For the general reader. Wöhler’s first research subject was the chemistry of cyanogen, a gas made of carbon and nitrogen, and of the cyanate salts related to it. These substances sit on the border of inorganic and organic chemistry. From them he obtained, in 1824, oxalic acid, a compound found in sorrel and rhubarb, and from them in 1828 he would obtain urea.
- Write the chemistry of cyanogen and cyanate as pseudohalogen and pseudohalide.
- Balance the hydrolysis of cyanogen to ammonium oxalate.
- Distinguish cyanate, isocyanate and fulminate.
Cyanogen as a pseudohalogen
Gay-Lussac had isolated cyanogen, \(\mathrm{(CN)_2}\), in 1815 and shown that the group CN passes through reactions like a single element, much as chlorine does. Wöhler studied the oxidation products of this group, the cyanates \(\mathrm{OCN^-}\), and the corresponding thiocyanates.
Cyanogen behaves like a halogen \(\mathrm X_2\): it disproportionates in alkali, \(\mathrm{(CN)_2}+2\,\mathrm{OH^-}\to\mathrm{CN^-}+\mathrm{OCN^-}+\mathrm{H_2O}\), just as \(\mathrm{Cl_2}+2\,\mathrm{OH^-}\to\mathrm{Cl^-}+\mathrm{OCl^-}+\mathrm{H_2O}\). Cyanide forms an insoluble silver salt, a weak acid HCN, and complex ions, as halides do.
Oxalic acid from cyanogen (1824)
An aqueous solution of cyanogen slowly deposits a brown solid and yields, among other products, ammonium oxalate. The overall hydrolysis of the C–C-bonded skeleton is
\[ \mathrm{N{\equiv}C{-}C{\equiv}N} + 4\,\mathrm{H_2O} \longrightarrow \mathrm{(NH_4)_2C_2O_4}. \]Since cyanogen could be prepared from mineral sources, this was formally a synthesis of a plant acid from inorganic matter, four years before urea. It attracted little attention, partly because oxalic acid was regarded as lying on the border of organic chemistry, and partly because the nitrogen-carbon compounds themselves were of animal origin.
Three ions, one composition
The ions \(\mathrm{OCN^-}\) (cyanate), \(\mathrm{CNO^-}\) (fulminate) and the covalent isocyanate group \(\mathrm{{-}N{=}C{=}O}\) show how connectivity changes properties. Cyanic acid exists in solution and vapour mainly as the tautomer isocyanic acid, \(\mathrm{HN{=}C{=}O}\), which is the reactive species in the urea synthesis.
Exercise 4.1Check the balance of the cyanogen hydrolysis above. How many grams of ammonium oxalate can 1.00 g of cyanogen give?
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Exercise 4.2Assign oxidation states to carbon in \(\mathrm{CN^-}\), \(\mathrm{OCN^-}\) and \(\mathrm{(CN)_2}\) (take N as −3, O as −2). Use them to show that the alkaline reaction of cyanogen is a disproportionation.
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Urea, 1828, and the vitalism story
For the general reader. Urea is the main nitrogen compound in urine. In 1828 Wöhler made it in a flask from ammonium cyanate, a salt prepared from mineral starting materials. Later textbooks presented this as the moment chemistry overthrew vitalism, the belief that only living things can make organic compounds. Historians now see it differently. For Wöhler and his contemporaries the striking fact was that two substances with the same composition, a salt and a neutral organic compound, could turn into one another. It was a case of isomerism.
- Write Wöhler’s two routes to urea and the modern mechanism.
- Analyse the reaction kinetics as a second-order ionic reaction.
- Assess the historiography: what the synthesis did and did not show.
The experiments
Wöhler tried to prepare ammonium cyanate by double decomposition, for example from silver cyanate and ammonium chloride, or from lead cyanate and aqueous ammonia. On evaporation the solution did not give ammonium cyanate. It gave colourless crystals that did not behave like a cyanate: acids released no cyanic acid, and bases released no ammonia. Comparing them with urea from urine, he found them identical. He published the result in Annalen der Physik und Chemie in 1828 under the title “On the artificial formation of urea.”
\[ \begin{aligned} \mathrm{AgOCN} + \mathrm{NH_4Cl} &\longrightarrow \mathrm{AgCl}\downarrow + \mathrm{NH_4OCN}\\ \mathrm{Pb(OCN)_2} + 2\,\mathrm{NH_3} + 2\,\mathrm{H_2O} &\longrightarrow \mathrm{Pb(OH)_2}\downarrow + 2\,\mathrm{NH_4OCN}\\ \mathrm{NH_4^+} + \mathrm{OCN^-} \rightleftharpoons \mathrm{NH_3} + \mathrm{HNCO} &\longrightarrow \mathrm{CO(NH_2)_2} \end{aligned} \]In aqueous solution ammonium cyanate isomerizes to urea. The rate is proportional to \([\mathrm{NH_4^+}][\mathrm{OCN^-}]\), consistent with a pre-equilibrium proton transfer to give ammonia and isocyanic acid, followed by nucleophilic addition of ammonia to the C=N bond of \(\mathrm{HN{=}C{=}O}\). The equilibrium lies strongly on the side of urea.
The kinetics were worked out by James Walker and Frederick Hambly in 1895, an early example of a reaction whose rate depends on the product of two ion concentrations.
Myth and history
Wöhler’s letter to Berzelius dwelt on isomerism and on the playful point that urea could now be made without a kidney. Berzelius praised the result and added urea to his examples of isomerism. Neither man treated it as a refutation of vital force. The cyanate came from substances such as horn or blood in some preparations, so a strict vitalist could object that organic origin had not been excluded. The overthrow of vitalism was gradual. Hermann Kolbe’s synthesis of acetic acid from carbon disulfide (1845) and Marcellin Berthelot’s syntheses in the 1850s and 1860s did more to show that organic compounds can be built from the elements. The heroic version grew in later histories and obituaries, and a 2000 survey by Peter Ramberg found it in most chemistry textbooks.
Exercise 5.1Starting from 10.00 g of silver cyanate and excess ammonium chloride, what is the maximum mass of urea? What mass of silver chloride precipitates? (AgOCN 149.89, AgCl 143.32, urea 60.06.)
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Exercise 5.2Suppose the conversion obeys \(-\frac{d[\mathrm{OCN^-}]}{dt}=k[\mathrm{NH_4^+}][\mathrm{OCN^-}]\) and both ions start at \(c_0\). Derive the half-life and show it depends on \(c_0\). If \(k=5.0\times10^{-3}\ \mathrm{L\,mol^{-1}\,min^{-1}}\) at a given temperature (an illustrative value), find the half-life at \(c_0=0.20\) and \(0.020\ \mathrm{mol\,L^{-1}}\).
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Exercise 5.3Give two chemical tests Wöhler could use to show that his crystals were not ammonium cyanate.
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Aluminium, beryllium, yttrium
For the general reader. Some metals hold onto chlorine or oxygen so tightly that ordinary chemistry cannot free them. Wöhler used a stronger grip: potassium, the most reactive metal then available. Heated with the dry chloride, potassium takes the chlorine and leaves the metal behind. In this way he obtained aluminium in 1827 and beryllium and yttrium in 1828.
- Write the reductions and explain the need for anhydrous chlorides.
- Use enthalpies of formation to see why potassium works.
- Follow aluminium from a laboratory curiosity to the Hall–Héroult process.
The method
Hans Christian Ørsted had prepared anhydrous aluminium chloride in 1825 and reduced it with potassium amalgam, obtaining a lump of metal whose purity was uncertain. Ørsted did not pursue it and agreed that Wöhler should continue. Wöhler could not reproduce Ørsted’s result, and instead heated anhydrous aluminium chloride with potassium in a covered crucible. After washing away the potassium chloride, a grey metallic powder remained. In 1845 he obtained small fused pieces and described the metal’s properties.
The reaction is driven by the much larger enthalpy of formation per chlorine of KCl than of the chloride being reduced. The chloride must be anhydrous: a hydrated chloride would give oxide or hydroxide, and water would react violently with potassium.
Beryllium was isolated independently and in the same year by Antoine Bussy in Paris. Wöhler introduced the name beryllium, from the mineral beryl; in France the name glucinium persisted into the twentieth century. His yttrium was impure, since the yttria earth of the time still contained other rare earths. In the 1850s Henri Sainte-Claire Deville replaced potassium by cheaper sodium and produced aluminium on a small industrial scale. It remained a costly metal until 1886, when Charles Martin Hall and Paul Héroult independently invented the electrolysis of alumina dissolved in molten cryolite.
Exercise 6.1Using \(\Delta_fH^\circ\) values \(\mathrm{AlCl_3(s)}\ -704\), \(\mathrm{KCl(s)}\ -437\) and \(\mathrm{BeCl_2(s)}\ -490\ \mathrm{kJ\,mol^{-1}}\), estimate the reaction enthalpies of the two reductions.
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Exercise 6.2How many grams of potassium are needed per gram of aluminium, and how many grams of sodium in Deville’s process? Why did the change matter?
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Exercise 6.3In the Hall–Héroult process, aluminium is deposited at the cathode from \(\mathrm{Al^{3+}}\). What charge is needed per kilogram? At a cell voltage of 4.5 V, what is the electrical energy in kWh per kg?
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With Liebig: benzoyl, amygdalin, uric acid
For the general reader. Wöhler and Liebig published together on three great subjects. In 1832 they showed that a group of atoms, benzoyl, survives through a whole family of compounds. In 1837 they found that a substance from bitter almonds is split by a plant extract into sugar, the almond-scented oil and prussic acid. And in 1838 they published a long study of uric acid, describing more than a dozen new compounds. Each opened a field: radicals, enzymes and glycosides, and the chemistry of purines.
- Recall the benzoyl series and the radical concept.
- Write the hydrolysis of amygdalin and identify the role of emulsin.
- Relate uric acid to alloxan, allantoin and urea.
Benzoyl (1832)
Oil of bitter almonds, benzaldehyde \(\mathrm{C_6H_5CHO}\), gave benzoic acid, benzoyl chloride, bromide, iodide and cyanide, and benzamide, all containing the group \(\mathrm{C_6H_5CO}\). The details are in Lesson 06 of the Liebig module. Wöhler drafted the paper.
Amygdalin and emulsin (1837)
Amygdalin had been isolated from bitter almonds in 1830 by Pierre Robiquet and Antoine Boutron-Charlard. Wöhler and Liebig found that it does not itself contain benzaldehyde or hydrocyanic acid, but that a protein-rich extract of almonds, which they called emulsin, breaks it down in water into sugar, benzaldehyde and hydrogen cyanide.
Amygdalin is the gentiobioside of mandelonitrile. β-Glucosidases remove the two glucose units, and the cyanohydrin then falls apart into benzaldehyde and HCN.
This was one of the first studies of a reaction caused by a soluble ferment, and amygdalin became the prototype of the glycosides, compounds of a sugar with a non-sugar part.
Uric acid (1838)
Their joint memoir on the nature of uric acid ran to about a hundred pages and described some fourteen new substances obtained by oxidizing uric acid and transforming the products. They named alloxan, from allantoin and oxalic acid, and established that urea is among the oxidation products. They remarked that the work made the synthesis of all organic substances in the laboratory appear not only probable but certain. The structures had to wait for Adolf von Baeyer in the 1860s and for Emil Fischer’s purine chemistry at the end of the century.
Exercise 7.1Check the balance of the amygdalin equation. How much HCN can 1.00 g of amygdalin release? (Amygdalin 457.4 g mol⁻¹, HCN 27.03.)
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Exercise 7.2Uric acid is \(\mathrm{C_5H_4N_4O_3}\). Compute its nitrogen percentage and compare it with urea’s. Why did both matter to physiologists studying the excretion of nitrogen?
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Quinone and hydroquinone
For the general reader. Quinone is a yellow compound that can take up two hydrogen atoms to become a colourless one, hydroquinone, and give them back again. Wöhler studied this pair in the 1840s, named hydroquinone, and described the dark green crystals that form when the two are mixed. The reversible pair later became a standard electrode for measuring acidity and a model for the electron carriers of living cells.
- Write the quinone/hydroquinone couple as a two-electron, two-proton reaction.
- Derive the pH dependence of its potential.
- Use the quinhydrone electrode to measure pH.
The pair
Hydroquinone had been obtained in 1820 by Pierre-Joseph Pelletier and Joseph Caventou by dry distillation of quinic acid. Wöhler, working on quinone, reduced it to the colourless compound he named hydroquinone (1843–44), and described quinhydrone, a 1 : 1 molecular compound of the two that forms dark green crystals. It is now understood as a charge-transfer complex. His formulas used incorrect atomic weights; the modern formulas are \(\mathrm{C_6H_4O_2}\) and \(\mathrm{C_6H_6O_2}\).
For \(\mathrm{Q} + 2\,\mathrm{H^+} + 2\,e^- \rightleftharpoons \mathrm{QH_2}\) with standard potential \(E^\circ\approx0.699\) V at 25 °C,
\[ E = E^\circ - \frac{RT}{2F}\ln\frac{[\mathrm{QH_2}]}{[\mathrm Q][\mathrm{H^+}]^2}. \]Quinhydrone dissolves to give \([\mathrm Q]=[\mathrm{QH_2}]\), so \(E=E^\circ-\frac{RT\ln10}{F}\,\mathrm{pH}=0.699-0.0592\,\mathrm{pH}\) volts at 25 °C.
Einar Biilmann introduced the quinhydrone electrode for pH measurement in 1921. It was widely used until the glass electrode replaced it. Quinones are also the mobile electron carriers of respiration and photosynthesis (ubiquinone, plastoquinone).
Exercise 8.1A platinum wire in a solution saturated with quinhydrone reads \(+0.464\) V against the standard hydrogen electrode at 25 °C. Find the pH.
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Exercise 8.2Why does the quinhydrone electrode fail above about pH 8?
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Silicon, boron, silane, acetylene
For the general reader. In the 1850s and 1860s Wöhler turned to the light non-metals. With the French chemist Henri Sainte-Claire Deville he made crystalline boron and silicon. With Heinrich Buff he discovered silane, a hydride of silicon that bursts into flame in air. And in 1862 he made calcium carbide and found that water turns it into acetylene, the reaction that later lit miners’ lamps and fed the first acetylene industry.
- Write the preparation of silane from a metal silicide and acid.
- Compare carbon and silicon hydrides and explain silane’s pyrophoricity.
- Do the stoichiometry of carbide and acetylene.
Silane (1857)
Buff and Wöhler treated an aluminium silicide with hydrochloric acid and obtained a spontaneously flammable gas, which they called siliciuretted hydrogen. Today silane is usually made the same way from magnesium silicide:
\[ \mathrm{Mg_2Si} + 4\,\mathrm{HCl} \longrightarrow 2\,\mathrm{MgCl_2} + \mathrm{SiH_4}, \qquad \mathrm{SiH_4} + 2\,\mathrm{O_2} \longrightarrow \mathrm{SiO_2} + 2\,\mathrm{H_2O}. \]Si–H bonds are weaker than C–H bonds and polarized with hydrogen negative (Si is less electronegative than H), while Si–O bonds are much stronger than C–O bonds. Silicon has accessible coordination numbers above four. As a result silane is kinetically labile toward oxygen and water, and ignites in air, whereas methane is inert at room temperature.
The systematic chemistry of the silicon and boron hydrides was developed by Alfred Stock from 1912. Silane is now the main source of thin silicon films in the semiconductor and solar-cell industries.
Calcium carbide and acetylene (1862)
Wöhler prepared calcium carbide and found that water decomposes it to ethyne (acetylene) and calcium hydroxide:
\[ \mathrm{CaC_2} + 2\,\mathrm{H_2O} \longrightarrow \mathrm{C_2H_2} + \mathrm{Ca(OH)_2}. \]In 1892 Thomas Willson in North America and Henri Moissan in France independently found that lime and coke in the electric arc furnace give carbide cheaply, \(\mathrm{CaO}+3\,\mathrm C\to\mathrm{CaC_2}+\mathrm{CO}\). Acetylene from carbide then lit lamps, cut and welded steel, and fed the early organic chemical industry.
Exercise 9.1What volume of acetylene at 0 °C and 1 atm can 1.00 kg of pure calcium carbide yield? Commercial carbide gives about 300 L per kg. Estimate its purity.
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Exercise 9.2How much silane, in litres at 25 °C and 1 atm, can 10.0 g of magnesium silicide yield, if the reaction were quantitative? Why does the real yield fall well short?
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Exercise 9.3Average bond enthalpies are about C–H 413, Si–H 318, C–O 358 and Si–O 452 kJ mol⁻¹. Use them to explain why the hydrolysis \(\mathrm{SiH_4}+2\,\mathrm{H_2O}\to\mathrm{SiO_2}+4\,\mathrm{H_2}\) is favourable while the analogous reaction of methane is not observed.
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Minerals, meteorites and analysis
For the general reader. Much of Wöhler’s work was patient analysis of minerals: what elements a rock contains and in what proportions. This work settled the identity of vanadium, unmasked the “metallic titanium” found in furnace slag, and found carbon compounds in a meteorite. It also produced his textbooks of analysis, used across Europe and translated into English.
- Follow the vanadium story as a lesson in identifying an element.
- Compute a mineral’s composition from its formula.
- See how Wöhler used humour in theoretical debate.
Vanadium (1831)
In 1801 Andrés Manuel del Río in Mexico found a new metal in a brown lead ore, but withdrew his claim after Hippolyte Collet-Descotils declared it impure chromium. Around 1830 Nils Gabriel Sefström announced a new element from Swedish iron ore and named it vanadium. Wöhler, who had been examining del Río’s Mexican ore, showed in 1831 that the two were the same element, vindicating del Río. The name vanadium stayed.
Titanium “metal” and meteorites
Copper-coloured cubic crystals found in the hearths of iron blast furnaces were thought to be metallic titanium. In 1850 Wöhler showed that they contain titanium combined with carbon and nitrogen, now understood as titanium carbonitride. In the late 1850s he analysed the carbonaceous meteorite that fell at Kaba in Hungary in 1857 and found organic matter in it, one of the first detections of carbon compounds in a meteorite.
Grundriss der Chemie (inorganic) and Grundriss der organischen Chemie (from 1840) went through many editions in his lifetime. Die Mineralanalyse in Beispielen (1861) taught analysis through worked examples.
A satire
In 1840 Liebig’s Annalen printed a letter from Paris signed “S. C. H. Windler” (a pun on Schwindler, swindler). It reported that every atom of manganese acetate had been replaced, one by one, by chlorine, while the compound kept its type, and that fabrics of such pure-chlorine substances were in fashion in London. The target was the extreme form of Jean-Baptiste Dumas’s substitution theory. The author was Wöhler.
Exercise 10.1Vanadinite is \(\mathrm{Pb_5(VO_4)_3Cl}\). Compute the mass percentage of vanadium. (Pb 207.2, V 50.94, O 16.00, Cl 35.45.)
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Exercise 10.2Manganese(II) acetate is \(\mathrm{Mn(CH_3COO)_2}\). How many atoms would “Windler” have had to replace to reach a compound made only of chlorine? What point was the satire making?
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The Göttingen laboratory, 1836–1882
At Göttingen Wöhler was professor of chemistry and pharmacy, director of the laboratory, and inspector general of pharmacies in the Kingdom of Hanover, a post that took him on inspection tours in the early years. He built up Stromeyer’s laboratory into one of the largest teaching institutions in Europe, modelled in part on Liebig’s at Giessen. By his own count, the number of students who passed through it rose from about 1 750 in 1845–52 to about 3 550 in 1860–66. By 1857 it had more than a hundred practical students and three assistants.
Among those who studied or took doctorates with him were Hermann Kolbe, Rudolph Fittig, Heinrich Limpricht, Friedrich Konrad Beilstein, Georg Städeler, Hans Hübner, Bernhard Tollens, Theodor Zincke, Albert Niemann, Wilhelm Kühne and Augustus Voelcker. Niemann isolated cocaine from coca leaves in Wöhler’s laboratory around 1859–60. Many Americans came to Göttingen, and Wöhler’s pupils staffed chemistry departments on both sides of the Atlantic.
He was a member of the Göttingen Academy of Sciences from 1837 and co-edited Liebig’s Annalen from about 1838. He gave his last lectures in the early 1870s and was succeeded as professor in 1874 by his former student Hans Hübner, who shared direction of the laboratory with him until his death.
DiscussionWöhler and Liebig ran similar research schools but had opposite temperaments: Liebig combative and theoretical, Wöhler cautious and experimental. Using their students as evidence, discuss how the character of a teacher shapes a school.
Friend, mediator, legacy
Wöhler was known for his good humour and his dislike of bitter disputes. He remained loyal to Berzelius, and for years tried to soften the quarrels between Berzelius and Liebig, and between Liebig and almost everyone else. His correspondence with Liebig, running from 1829 to 1873, was edited by August Wilhelm von Hofmann and published in 1888; it records two very different men who never broke with one another. In later life he admitted that he had not kept up with the new structural theory and preferred the bench to speculation.
His honours included foreign membership of the Royal Society (1854), the Prussian Pour le Mérite for Sciences and Arts (1864), election as foreign associate of the Paris Académie des sciences (1864), the Copley Medal (1872) and the Cothenius Medal of the Leopoldina (1880). He was an honorary member of the German Chemical Society and its president in 1877. He died in Göttingen on 23 September 1882, aged 82, and was buried in the Stadtfriedhof. A bronze statue was unveiled in Göttingen in 1890. The mineral wöhlerite and a lunar crater bear his name.
Legacy
- Organic chemistry: the urea synthesis as a case of isomerism; isomerism and compound radicals with Liebig; amygdalin and the first studies of enzymatic hydrolysis; the uric acid family.
- Inorganic chemistry: first isolation of aluminium, beryllium and yttrium; silane; calcium carbide and acetylene; crystalline boron and silicon; the identity of vanadium.
- Teaching: the Göttingen laboratory and its thousands of students; widely used textbooks of analysis.
- Communication: German translations of Berzelius’s textbook and annual reports; co-editorship of the Annalen.
Final projectFind three chemistry textbooks, of different dates, that mention the urea synthesis. Compare what they claim with the account in Lesson 05, and write a two-page essay on how and why the story changed.
Sources and further reading
Biography
- Friedrich Wöhler, Wikipedia; and the German article Friedrich Wöhler.
- Wöhler, Friedrich, Neue Deutsche Biographie and Allgemeine Deutsche Biographie (Deutsche Biographie).
- Wöhler, Friedrich, Complete Dictionary of Scientific Biography, via Encyclopedia.com.
- Science History Institute, Justus von Liebig and Friedrich Wöhler.
- A. W. Hofmann (ed.), Aus Justus Liebig’s und Friedrich Wöhler’s Briefwechsel in den Jahren 1829–1873, Vieweg, 1888.
- O. Wallach (ed.), Briefwechsel zwischen J. Berzelius und F. Wöhler, Engelmann, 1901.
Chemistry
- F. Wöhler, Ueber künstliche Bildung des Harnstoffs, Annalen der Physik und Chemie 88 (1828) 253–256.
- F. Wöhler, Ueber das Aluminium, Annalen der Physik und Chemie 11 (1827).
- F. Wöhler and J. Liebig, Untersuchungen über das Radikal der Benzoesäure, Annalen der Pharmacie 3 (1832).
- F. Wöhler and J. Liebig, Untersuchungen über die Natur der Harnsäure, Annalen der Pharmacie 26 (1838).
- H. Buff and F. Wöhler, Ueber eine Verbindung von Silicium mit Wasserstoff, Annalen der Chemie und Pharmacie 103 (1857).
- P. J. Ramberg, The death of vitalism and the birth of organic chemistry: Wöhler’s urea synthesis and the disciplinary identity of organic chemistry, Ambix 47 (2000) 170–195.
- J. Walker and F. J. Hambly, Transformation of ammonium cyanate into urea, Journal of the Chemical Society, Transactions 67 (1895).
- Wöhler synthesis, Aluminium, Beryllium, Silane, Calcium carbide, Vanadium, Amygdalin and Hydroquinone, Wikipedia, history sections.