A C T A U N I V E R S I T A T I S L O D Z I E N S I S
FOLIA CHIM ICA 1 3 ,2 0 0 4
JUSTUS LIEBIG LIFE AND WORK
by Helmut Gebelein
J u stu s L ieb ig U niversity, D ep a rtm en t o f C h em ica l D idactics, H ein rich B u ff-R in g 58, 3 5 392 G iessen, G erm any
Fig. 1. Freiherr Justus von Liebig, 1864
L iebig was not only one o f the m ost prom inent chem ists o f the 19th century, he had also done im portant work in agriculture and in nutrition. He even w rote articles about philosophical problem s, he im proved a special m ethod o f fresco painting, and with his C hem ical Letters he produced one o f the best books on chem istry for the laym en. A sim ilar work on m odern chem istry is still lacking.
Liebig was born on the 12th o f May 1803, in D arm stadt, a town som e 20 kilom etres to the south o f Frankfurt.
At this time D arm stadt was the capital o f H essen-D arm stadt, one o f the small G erm an states. Duke Ludwig 1 o f H essen-D arm stadt was interested in the advancem ent o f the sciences. He even had a university at G iessen, founded in 1607. T his university is today called Justus Liebig-U niversity after its most prom inent scientific scholar.
L iebig’s father had a drysalt and hardware shop and he ow ned a small laboratory w here he produced drugs and materials, e.g. pigm ents for colours.
T hrough the father’s laboratory Justus becam e interested in chemical processes already in his youth and he wanted to becom e a chem ist.
He read all the books on chem istry he could get hold of. The court library w here he borrow ed most of these books was unfortunately not very up to date. He could not learn modern chem istry in this way. But it m ight be that his later interest in history o f chem istry came from these readings.
But this life didn’t start very prom isingly. At the age o f 14 he left school without any qualification. It must be said that in this tim e this was not unusual.
In H eppenheim , a small town to the south o f Darm stadt, he started a apprenticeship to an apothecary, but after 6 months he had to quit. It is most probable that his father was not able or willing to pay for his son. He him self wrote later that he had to leave after 10 month because he had conducted dangerous experim ents.
For the next two years he stayed at home. On the m arket place he observed a man producing caps of silver fulm inate. He investigated this reaction and published the results in his first article in 1822 with the help o f Professor Karl W ilhelm G ottlob K astner (1783-1853)', an acquaintance o f his father. K astner even invited him to study chem istry at the U niversity o f Bonn. At this time it was possible to study w ithout any formal school education. In 1820 he began to study chem istry in Bonn. When K astner went to Erlangen in 1821, he took Liebig with him.
As a m em ber o f a student society he ran into political trouble and - not to be arrested - had to flee hom e to Darmstadt. The Duke o f H essen-D arm stadt, Ludw ig I. - again with the help o f Kastner - sent him to Paris, at this tim e the most im portant university for chemistry.
There he met not only the important French chem ists like Joseph Louis Gay Lussac (1778-1850), and Louis Jacques Thenard (1777-1857) but also A lexander von Hum boldt, who was very im pressed by this young scientist and supported him.
In the m eantim e Kastner m anaged to arrange that Liebig could get his doctorate at the U niversity of Erlangen in absentia. His thesis was entitled About
the relation o f m ineral chem istry to the chem istry o f pla n ts ( Ü ber (las Verhältnis der M ineralchem ie zu r Pflanzenchem ie) and touchcd on a problem he was later
on very m uch engaged with. Now he was able to start an academ ic career. W hen he cam e back to D arm stadt on the advice o f K astner and H um boldt, Ludw ig I. nom inated him for the position o f Professor o f Pharm acy and C hem istry at his university in Giessen.
Here he ran into a lot o f problem s, as he was appointed by the duke w ithout the university being consulted. Only when he gained the interest o f the students did the attitude o f the university change. In 1833 his private institute was integrated into the university as the chemical institute.
In 1826 he m arried H enriette M oldenhauer and with her he had 5 children: H erm ann, G eorg, Agnes, Johanna and M arie.
In 1831 he - or probably his glass blow er - invented the K aliapparat with five glass bulbs. W ith this invention, elem entary analysis was dram atically im proved. T he K aliapparat becam e the em blem o f L iebig’s students, which they wore as a badge.
From 1831 Liebig belonged to the publishing team o f the M agazine o f
P harm acy (M agazin fiir Pharm azie). From 1840 on it was published under the
nam e o f A nnals o f C hem istry and Pharm acy (A nnalen d e r C hem ie und
Pharm azie). In this function he also acted as a com petent ju d g e o f the articles
although his criticism was - according to Partington - som etim es beyond all reason.
In 1839 he was able to build his new laboratory. W ith this design he created the prototype for all laboratories in universities and industry. T he old laboratory still looked like that o f an alchemist.
Fig. 3. The new laboratory in the Liebig M useum G iessen
In 1845 he was ennobled and from this tim e on he was Justus Freiherr von Liebig. He him self had urged the duke to take this step, arguing that he should have the sam e title as the famous French chemists.
Until 1852 Liebig was a professor in G iessen. D uring this time 700 students studied in Giessen, am ong them nearly 200 from foreign countries. An im pressive num ber, as at this time the town had 5500 inhabitants and around 300 students in all faculties.
Then the King o f B avaria invited him to com e to M unich. T here he was also appointed P resident o f the Bavarian Academ y o f Science.
In M unich he was given a great house, a laboratory and a lecture hall with 300 seats.
At one o f his first public lectures, there was an incident. He perform ed the experim ent o f burning carbon disulphide in laughing gas (nitrous oxide). The public was enthusiastic, so he decided to repeat the experim ent. But he m ade a mistake: instead o f laughing gas he took a vessel with oxygen, the result was an explosion, and a few persons, even som e o f the Royal Fam ily w ere injured, fortunately not seriously. In the journal A llgem eine A u g sb u rg er Z eitung he reported - anonym ously - about this incident and w rote that he w as not blam ed for his m istake and that the King even asked him about his w ounds.
He died on the 18"' o f M arch 1873 in M unich and is buried there.
Let us now have a look at L iebig’s most im portant contributions to the sciences.
C hem istry as it is regarded today is a young science. It can be said that it started with the w ork o f A ntoine-Laurent Lavoisier (1743-1794). His theory o f
burning, which states that oxygen is taken up in this process, can be regarded as the starting point o f m odern chemistry.
In his C hem ical Letters Liebig describes the strange celebration in which M adam e L avoisier in the costum e of a priestess throw s the books o f the phlogistonic system into the fire whilst a requiem is played. L avoisier did this to prom ote his system . Wc, in our time, cannot find this celebration very am using.
The new theory o f burning was not readily accepted in Germ any. The old theory - the phlogistonic theory - was form ulated by the G erm an alchem ists Johann Joachim B echer (1635-1682) and Georg Ernst Stahl (1660-1734). This theory explains burning as a loss of a substance nam ed phlogiston. It seems thal national interests may have played a role in the lack o f acceptance o f the new theory.
C hristoph G irtanner, in a book on antiphlogistonic chem istry, w rote that he prom oted this new system , which was opposed by all great chem ists, only because it was true, and that he would defend it only as long as he was convinced that it was true.
T he long tradition o f alchemy had com e to an end, and the modern chem istry began. In contrast to his contem poraries, Liebig regarded alchem y as an im portant epoch in the history o f science, as can be read in his Chem ical
Letters. T here he states that alchemy was, with regard to the know ledge of
nature, ahead o f all other sciences. It was only because they w ere unaw are o f the history o f chem istry that m ost chem ists, overestim ating their own knowledge, looked back w ith disgust on the period of alchemy as if the very learned men like Francis Bacon, Spinoza, Leibniz were interested in absolutely senseless ideas.
But at the time o f Liebig modern chem istry was only in its beginnings. One reason was that in 1850 only 52 o f the 92 naturally-existing elem ents were known, and that it was not clear, which substances were really elem ents. As a result more than 170 spurious elem ents were reported in the 19lh century. A nalyzing substances in order to find out if they can be reduced to an elem entary state was therfore o f the greatest interest.
Not very m uch was known about chem ical com pounds too, due to the lack o f good analytic methods. It can be said that the developing ot analytical m ethods was o f the highest im portance at this time.
The study o f chem istry can be regarded as consisting o f analytical, preparative, and theoretical chem istry. Liebig had contributed to all these branches.
Liebig started in Giessen as a pharm aceutical chem ist. This is not surprising since chem istry was part o f medicine at this time.
In 1831 lie was able to produce chloroform (C H C I3), used as an anaesthetic for quite a long time. In his analysis he could not find the hydrogen atom , so the chem ical form ula (C C lj) which he published was wrong. W ith the preparation o f chloral hydrate he produced the first synthetic sleeping drug, which was used for the first time by O scar Liebreich in 1869, only a few years after Liebig had produced it.
Liebig and his students w orked in the new field o f organic chem istry. At this tim e scientists assum ed that organic substances could only be synthesised in the living organism . They could be analysed by men but not produced from elem ents. A nalysis o f organic substances was therefore one o f the most prom inent research program s o f the time.
Again L avoisier was the first to analyse organic com pounds by burning and m easuring the volum es o f w ater vapour and carbon dioxide. H ow ever, with this m ethod he had little success. The French chem ists im proved the method. L ouis-Jacques T henard (1777-1857) used potassium chlorate in 1810, and Joseph-L ouis G ay-L ussac (1778-1850) em ployed copper oxide in 1815 as an oxidizing agent. But still the elem entary analysis o f organic com pounds was a com plicated, tim e consum ing and tricky art. A fter burning the com pound, the volum e o f the w ater vapour was m easured to determ ine the am ount o f hydrogen, then the carbon dioxide gave the am ount o f carbon in the com pound. The am ount o f oxygen could be found only by calculation from this data. In this way it took 13 years for M ichel Eugène C hevreul (1786-1889) to analyse the fats he had separated.
W ith L iebig’s im provem ents it no longer took m onths but only days to perform an analysis, and m oreover, it could now be done by laboratory assistants.
Fig. 4: Elementary analysis. Original apparatus and analysis o f sugar. On the left copper oxid e, next to it the sugar.
T he m ain im provem ent was the Kaliapparat with its five glass bulbs. W ith this device a com plete absorption o f the carbon dioxide w as possible, and the increase in w eight could be easily m easured, as the K aliapparat could be
hung on the balance. O therw ise the m ovem ent o f the liquid w ould influence the w eighting.
Fig. 5. T he Kaliapparat hanging at the balance
T he great chem ist Jons-Jakob Freiherr von B erzelius (1779-1848) criticised Liebig for not honouring other scientists sufficiently in his works. This was the beginning o f an open conflict betw een these tw o great chem ists.
W ith L ieb ig ’s im provem ents the elem entary analysis o f organic com pounds was the standard m ethod until the beginning o f the 2 0 th century, when the N obel Prize w inner o f the year 1913, Fritz Pregl (1869-1930) developed the quantitative m icroanalysis.
Let us look at the analysis o f sugar. W e take 0.9 g o f sugar and will get ca. 0.54 g o f w ater and 4.14 g o f potassium carbonate.
T he content o f hydrogen in the probe o f sugar can be calculated:
„ 2 - 0 .5 4
H --- -- 0 .0 6 g 18
as w ell as that o f carbon:
„ 1 2 - 4 . 1 4
C = --- = 0.36g
138
T he content o f oxigene is calculated from the differences: 0.9 - 0.06 - 0.36 = 0.48 g
D ividing by 3, we get the relation C (1 2 ):0 (16):H (1) = 1:1:2
T hat m eans the form ula o f sugar can be either C H 20 or C 6H i20 6 or in general C nH2nO„.
At the time Liebig did his elem entary analysis it was not possible to know which o f the options was the right one. There were other m ethods needed, not yet developed. Liebig wrote for exam ple that in spite o f the differences o f acid o f sauerkraut, milk sugar, and cotton fibre the analysis show ed that these substances had the same com position. I must add that L ieb ig ’s results were not always w ithout any doubt. He never perform ed a calculation o f error with on his results.
T he advancem ent in elem entary analysis was not possible without the developm ent o f balances o f a higher accuracy. In the 19"' century the balance makers learned to build balances with an accuracy unattainable before. Liebig found even in Giessen a fine m echanic who was able to build such balances. But w eighting was still a tim e-consum ing job. Liebig sm oked, it is said, a lot of cigars, sitting in front o f the balance.
It m ust be rem em bered that this analysis gave no inform ation about the structures o f m olecules. Only at the end of the 19"’ century did chem ists begin to understand the im portance o f structural analysis, and only then were appropriate methods developed.
Som e o f L iebig’s im portant works are concerned with theoretical chem istry.
In 1824 he finished his work o f fulm inic acid (H O N C ) and the fulm inates. At the sam e time another young chem ist, Friedrich W ohler (1800- 1882) was w orking on cyanic acid (HOCN) and the cyanates. From these salts he was later able to synthesise urea.
G ay-Lussac rem arked on reading both reports that these two com pounds had the sam e atom ic com position. He inform ed Berzelius, w ho co u ld n ’t believe it, but after finding other exam ples, he nam ed such com pounds isom eric (Gr.: same parts). This was the first indication that com pounds are not ju st an assem blage o f atom s and that the ordering of the atoms plays a crucial role. Just as with the letters A, R, and T, the words RAT and A R T can be com posed, giving a different sense, another ordering of the atom s leads to m olecules with different characteristics.
Liebig and W ohler becam e good friends and collaborated from this lime on.
Already in earlier times acids were known. First acid fruit juices and vinegar, which can easily be produced from wine to give acetic acid were used. In the course o f time other acids, especially the mineral acids like hydrochloric acid, sulphuric acid were discovered. The salts o f these acids are found in m inerals. Therefore they are called mineral acids. Bases were less com m on, soda - sodium carbonate - was known in old Egypt, and potash - potassium carbonate - was extracted from wood ash.
A first theory o f acids and bases form ulated by L avoisier said that oxygen is the effective principle o f all acids. H ydrochloric acid does not contain oxygen so the theory did not fit all cases. C hlorine was not accepted for years as an elem ent, as is was still assum ed to contain oxygen to fit L av oisiers’ theory.
In 1838, Liebig going back to an idea o f Hum phrey Davy (1778-1829) from the year 1810, when the latter proposed hydrogen as the effective elem ent o f acids, and to the studies o f Thom as G raham (1805-1869) on the poly-protonic phosphoric acid, developed a theory o f acids and bases.
His definition says that an acid is a com pound w here hydrogen can be replaced by a metal. A still valid definition.
In the reaction o f an acid with a metal the developm ent o f hydrogen depends on the strength o f the acid. At the sam e time a strong acid will produce more hydrogen than a w eak acid. The weight o f hydrogen or the degree of its production is used to differentiate between strong and weak acids. T he m easure is the pH -value (abbreviated from pondus hydrogenium - w eight o f hydrogen - or potentia hydrogenium - strength o f the hydrogen production).
A first effort to bring order into the mass o f organic com pounds was the theory o f radicals. Liebig and W ohler invented a system o f radicals, saying that a group o f atom s can behave as a single atom. We would today call such groups “functional groups” . In this theory there was an im portant assum ption that the sam e rules are effective in organic and in inorganic chem istry. O rganic chem istry is not a special case anymore. O rganic com pounds can be synthesised in the laboratory - an im portant step to modern carbon chem istry.
Carl A ugust Steinheil (1801-1870) had the idea that m irrors o f silver instead o f bronze would im prove the quality o f his m irror-telescopes and asked Liebig for help. The Englishm an D raytoir had already tried to produce silver mirrors but had had no success. One o f the reason was the reaction o f silver with sulphur, resulting in the black silver sulphide, which m ade the m irror blind. Liebig was able to solve the problem and meet S teinheil’s needs by applying electrochem ically a layer o f copper over the silver deposit.
He then tried to go into the m irror production in Fiirth in Bavaria. At this time m irrors were still m ade with the help of m ercury, a poison - a very unhealthy m ethod not only for the workers but also for the buyers, as m ercury evaporates from these m irrors for years. A good exam ple o f this effect is - by the way - the Mad H atter in the fam ous novel by Lewis C aroll, A lice in the
W onderland, who has been poisoned with mercury.
T here w ere backlashes for Liebig. The glass used for the m irror production was not o f a sufficient quality and the silver m irrors had a different
2
reflection co lou r to that o f the m ercury-tin am algam m irrors. T his colour was not accepted by the ladies o f the time. Liebig wrote that especially in France it was im possible to produce his mirrors, because they reflected a yellow ish or green- yellow ish colour and, he continued, as the French ladies already had a yellow ish com plexion, they looked even m ore unattractive then they already were in his bright m irror. N ot very polite.
O nly at the end o f the century were silver m irrors successful due to safety regulations. T oday m ost m irrors have surfaces o f alum inium .
In M unich a new method for fresco painting was invented by a num ber o f artists. This m ethod, called stereochrom y, m ade the paintings not only w eatherproof but also fireproof by applying w ater glass in a special way to the paintings. A fter im proving it he had two landscapes and tw o allegories painted on the garden front o f his laboratory in M unich. Stereochrom y was also used for the decorations in theatres.
U nfortunately this paintings disappeared with the dem olition o f the building and only the drafts o f the two allegories can still be seen in the S urm ondt-L udw ig M useum in Aachen.
Fig. 7. The goddess Pomona as allegory o f agriculture. Draft by Ludwig Thiersch
There are quite a few chem ists who say Liebig was not a real chem ist but an agriculturist or nutritional scientist. It is true that in both fields he did a lot o f im portant work.
B eginning around 1830 he becam e m ore and m ore interested in these two fields. O ne o f the reasons was certainly the fact that in C entral Europe and also in H essen there had been poor harvests and great fam ines, even forcing a lot o f the population to em igrate to America.
Liebig was o f the opinion that the main interest o f science should be to im prove the life o f hum an beings. For him chem istry was in this respect the m ost im portant science. W hen through science and technology we are able to fulfil all needs o f hum an beings, revolutions will be at an end, he w rote, form ulating the hopes o f the industrial era. These hopes have still not been fulfilled.
In 1840 his book O rganic Chem istry in its A pplications to A griculture
and Physiology in short A griculture appeared sim ultaneously in Germ an,
English, and French. In this book he explains that the fertility o f the soil can only be preserved w hen the m inerals used by the plants are given back to the soil. A lot o f experim ents analysing the plants and the soil w ere perform ed to find out
the concentrations o f m inerals in the soil for an optim al grow th. U nfortunately, L iebig’s experim ents with fertilizers were com pletely unsuccessful. Liebig thought he had to take sparingly soluble m inerals to avoid their being w ashed out by the rain. W hen he read an article by the viticulturist J. Ph. B ro n n e r(1792- 1865), w ho w rote that he had noticed that soil could absorb the coloured substances o f liquid m anure and soluble salts, he changed his opinion in the 8'1' edition o f his Agriculture o f 1862. In this case he m entioned the w ork o f Bronner. He w rote that he had not taken into account the w isdom o f the C reator and for this he had recived his ju st deserved punishm ent.
W ith the soluble fertilizers he had som e successes. He even noticed that the soil could purify water. Therefore for the w aterw orks in London he proposed that w aste should be given back to the soil. This proposal was not picked up by the London authorities.
Fig. 8. The minimum tub
W ell know n is his m inim um tub. Fertilizing follow s the m inim um principle. T he elem ent which is in the low est concentration determ ines the grow th o f plants. T he idea which is norm ally attributed to L iebig had already been form ulated in 1828 by Carl Sprengel (1787-1859). L iebig m ust have know n his articles but he gave no credit to him.
Liebig, it m ust be said, was not a friend o f m ineral fertilization. He was a friend o f a recycling agriculture. All the substances in grow ing plants taken
from the field should be given back to the soil. O nly if this is, for w hatever reasons, not possible, is m ineral fertilization necessary and then it m ust be done in the right way. T he C hinese coolie who brings back all w aste to the field is his shining exam ple. In his C hem ical Letters Liebig described this in detail, even m entioning that in C hina you cannot leave the house w ithout going to the toilet as you w ould otherw ise take good things with you.
He w ould not have liked overproduction, ecological dam age by overfertilization. In his opinion men cannot interfere with nature w ithout being punished by it.
In his book O rganic C hem istry in Its A pplication to Physiology ancl
Pathology in short A nim al C hem istry he created the basis for a scientific theory
o f nutrition - although it contained a lot o f errors, partly due to the rudim entary know ledge o f his tim e.
A result was L iebig’s m eat extract.
u m fa d e n S p e is e n d e n k östlich m u n d e n d e n u n d s t ä r k e n d e n F le isc h g e sc h m a c k zu v e r le ih e n
Fig. 9. Advertising for L ieb ig's Meat extract
M eat extracts were already known, but again he m ade an im provem ent om itting the gelatine. Today it is only regarded as a sort o f spice, as it has, in fact, no nutritional value.
In his fam ily there were problem s with breast-feeding. He invented the first baby food, and the babies survived. The high rate o f infantile m ortality at that tim e was m ostly due to deficits in hygiene and in nutrition. W ith his substitute for m other m ilk and his food for babies a w hole industry started.
For an English girl who was suffering from tuberculosis and could no eat any more, he prepared a special soup and was able to help her. T his soup was a cold m aceration o f chicken meat with distilled water and a little hydrochloric acid.
He also invented an instant coffee. Every guest had to taste it, but only Liebig liked it.
Liebig was also an aggressive scientist. His criticism s were not always reasonable. Som etim es he corrected him self, as in his differences with Louis Pasteur (1822-1895). He d id n ’t like the idea that alcoholic ferm entation is perform ed by living cells. In his opinion it was a purely inorganic process. T ogether with W ohler he wrote a satire on Pasteur’s living cells, to show how ridiculous this idea was.
It should not be forgotten that he was also a great writer. W ith his
C hem ical Letters he produced a wonderful book about the chem istry o f his time.
The book has been translated into many languages - also into Polish - and is still worth reading.
In his later years he becam e interested in the philosophy o f nature. His main interest concentrated on Francis Bacon, Baron V erulam since 1619 (1561 - 1626). He wrote that the great authority o f Bacon was responsible for the lack of interest in theories in England. Liebig was a w ell-know n and accepted person in England. He taught a lot o f English students in Giessen. Even Queen Victoria was fond o f him. But with his criticism o f Bacon the English were not at all content. In an academ ic address. Induktion und Deduktion, he stated that chem istry is a deductive science. This stands in contradiction to Bacon, who regarded all sciences as inductive. Karl E. Popper (1902-1994), the fam ous philosopher o f science, cites this article favourably in his work.
Liebig was, in his time, one o f the most prom inent and famous scientists. He was a propagandist o f science and especially o f chem istry and o f himself. Even inventions he did not make were nam ed after him , like the Liebig cooler, an invention o f C hristian Ehrenfried W eigel (1748-1831) m ade in the year 1771.
His m ost im portant contribution was probably the training o f his students. He had learned in Paris that students should take part in the research process and he im proved this system system atically. This new system o f practical education in chem istry was responsible for the rise o f the chemical industry in G erm any, as he was always looking for application for the results o f science in industry.
W illiam H. Brock writes in his biography: ’’Liebig was a com plex hum an being, tull of contradictions and inner conflicts. At one m om ent, genial, charm ing, pleasant, and affectionate, in another he was difficult, em otional,
easily provoked, and on the lookout for quarrels. Always overw orked and overw orking, because of his obsessive determ ination to m ake chem istry the fundam ental science for m odern societies, it thrived. Liebig was wilful, but never arrogant.“
He will be regarded for all time without any doubt as an exam ple o f a great scientist, w hose interest was to work for the benefit o f m ankind.
R E F E R E N C E S
[ I ] Justus Liebig, O rg a n ic C hem istry in its A p p lic a tio n s to A g ricu ltu re a n d P hysiology. [2] Justus Liebig, O rg a n ic C hem istry in its A pplica tio n s to P hysiology a n d P athology. [3] Justus Liebig, C h em ica l Letters.
[4] Justus Liebig, R eden uiul A bh a n d lu n g en .
[5] W illiam H. Brock, J u stu s von Liebig. The C hem ical G a te ke ep e r, Cambridge, 1977. [6] S. H eilenz, D as L ieb ig -M u seu m in G iessen, G iessen, 1988.
17] V, Karpenko, The D isco very o f S u p p o se d N ew Elem ents. Two C en tu ries o f E rrors, Am bix, 27, 1980, S. 77 ff.
[8 1 Otto Kratz, D as W asserglas a n d d ie sch d n en Kilnste, Charivari, 7, 1 9 8 1, S 12-20. [9] J. R. A. Partington, A H isto ry o f C hem istry, London, 1964.
