# Biographies of Scientific Men/Liebig

Baron Gustus von Liebig and the Giessen Laboratory in 1840
LIEBIG
1803-1873
GERMANY'S great chemist was born at Darmstadt on 12th May 1803, the year that the Electorate of Hanover was seized and occupied by the army of Napoleon, and the violation of German territory by the seizure of the Due d'Enghein at Ettenheim, and his subsequent execution.
Leibig's natural aptitude for experiments suggested the idea that he would be suitable for an apothecary; consequently, his father selected this as the profession for his son. He did not, however, long continue this work, and was sent to the University of Bonn, and entered as a student of medicine. He left Bonn, and graduated at Erlangen University at the age of eighteen. In Liebig's student days the German professors, unlike teachers in this country, enjoyed a perfect "Lehrfreiheit" (freedom in teaching), by which is meant the liberty of choosing the subjects which they treat in their lectures, and of expressing their views upon them freely. German professors used to read their lectures (some few delivered ​them): it may easily be imagined how fatal such a practice was to the graces of elocution. Goethe alludes to it in Faust:—
Doch euch des Schreibens ja befleisst Als dictirt "euch der Heilig" Geist.
It may be mentioned that many parts of Faust are unintelligible to the reader who knows nothing of German university life.
During this period he studied natural science, and his progress was marked with such success that he was granted a pension or scholarship by the Grand Duke of Hesse-Darmstadt, which enabled him to continue his studies and researches. Liebig went to Paris in 1823. Having communicated a paper on fulminic acid to the Académie des Sciences, he was introduced to Alexander von Humboldt, Gay-Lussac, and other savants then living in the French capital. Liebig became a pupil in the laboratory of the famous chemist Gay-Lussac, discoverer of the law of volume. At the beginning of the nineteenth century there were only a few chemists in Germany, and this was the reason that he went to Paris.
In the same year that Liebig went to France, he began to perfect the method of organic or combustion analysis. The principle of the method is the one now used for determining the carbon, hydrogen, and oxygen in organic compounds. The compound is heated with copper oxide in a glass tube, and the carbon and hydrogen are ​oxidized to carbon dioxide and water, the former being absorbed by caustic potash, and the latter by calcium chloride. The method now in use differs from that of Liebig in only a few particulars, the principal of which is that gas has superseded charcoal.
In 1824 Liebig returned to Germany, having been appointed Professor of Chemistry in the University of Giessen—a seat of learning which he made famous throughout the world by means of his discoveries and teaching, and where he attracted students from all parts of Europe.
About this time Liebig gave special study to the cyanates, which were also being studied by Wöhler. The two young men became friends, recognized each others powers, and aided each other in scientific work, and many papers were published under their joint names. Liebig's researches were published in Poggendorff's Annalen; Liebig's Annalen der Chemie und Pharmacie; Handwörterbuch der reinen und angewandten Chemie; and Jahresbericht der Chemie: in all he published three hundred papers.
Liebig remained at Giessen for twenty-eight years, i.e., until 1852, when he accepted the chair of chemistry in the University of Munich. This was due to the influence of the King of Bavaria. His fame spread rapidly, and students filled his laboratory. Great enthusiasm was evinced at his lectures, and though not a fluent lecturer, the knowledge he imparted carried away his audience, ​for he taught living facts, not merely the dead ashes of science. The late Dr Hofmann, who was a pupil of Liebig, said of his master: "Nor was it so much the actual knowledge he imparted, as the wonderful manner in which he called forth the reflective powers of even the least gifted of his pupils. And what a boon was it, after having been stifled by an oppressive load of facts, to drink the pure breath of science such as flowed from Liebig's lips! What a delight, after having perhaps received from others a sack full of dry leaves, suddenly in Liebig's lectures to see the living, growing tree! We felt then, we feel still, and never while we live shall we forget, Liebig's marvellous influence over us; and if anything could be more astonishing than the amount of work he did with his own hands, it was probably the mountain of chemical toil which he got us to go through. Each word of his carried instruction, every intonation of his voice bespoke regard; his approval was a mark of honour, and of whatever else we might be proud, our greatest pride of all was having him for our master. Of our young winnings in the noble playground of philosophical honour, more than half were free gifts to us from Liebig; and to his generous nature no triumphs of his own brought more sincere delight than that which he took in seeing his pupils' success, and in assisting, while he watched, their upward struggle." Lucky was he who was under such a master.
​In 1840 (ever-memorable year), while at Giessen, Liebig published his famous and epoch-making work on agricultural chemistry, Die organische Chemie in ihrer Anwendung auf Agricultur und Physiologie. Although Davy, thirty years before, had published a work on Agricultural Chemistry, it was not until Liebig's book made its appearance that any great stride was made in the scientific principles of agriculture. This book is one of those few works which stand out from all others on the subjects of which they treat. It is undoubtedly the most important work on agriculture ever given to the world as the result of one man's researches and ideas. From the land of Kant, Fichte, Schelling, Schiller, and other philosophers, it is not surprising that we have such a far-reaching and philosophic work as Liebig's Die organische Chemie given to us.
That an increase of solubility in bones and other phosphates would be attended by an increased productive power in the crop, was the idea of Liebig. He, in 1840, recommended, in lieu of bones, the use of the substance long well known to chemists as the acid or superphosphate of lime, which is producible from bones and other phosphates by the action of oil of vitriol or sulphuric acid. Practice has since shown the great advantage of Liebig's suggestion.
The chief point of Liebig's famous book was to show that the humus of the soil is powerless to build up ​completely the various tissues of plants. He taught that the carbonic acid of the atmosphere was the principal source of the carbon in plants; that their hydrogen came from water, their nitrogen from ammonia present in the air and soil. The sulphur, which is an ingredient in the protoplasm ("the basis of life") of living plants, comes solely from the sulphates and sulphur compounds contained in the soil; and, finally, that the mineral ingredients found in the ashes of plants come from the soil in which they grow. Liebig further demonstrated that plants cannot live without these mineral ingredients, and that the humus of the soil is incapable of forming the sole nutrient material for plants.
Liebig says in his book (p. 174):—
Although the quantity of humus in a soil may be increased to a certain degree by an artificial cultivation, still, in spite of this, there cannot be the smallest doubt that a soil must gradually lose those of its constituents which are removed in the seeds, roots, and leaves of the plants raised upon it. The fertility of a soil cannot remain unimpaired, unless we replace in it all those substances of which it has been deprived.
Liebig's theory was a revolutionary movement on the accepted ideas of scientific agriculture which dawned at the commencement of the nineteenth century.
He supported his theory by well-conducted experiments, showing that fields containing an excess of humus ​did not produce more than fields in which this ingredient was deficient. Although Liebig's theory of plant nutrition was essentially a mineral theory, yet he understood that organic matter (humus) decomposes in a soil, giving rise to carbonic acid and ammonia; and these gaseous bodies are also valuable plant foods. Liebig fully established the following important laws of husbandry:—
(1) A soil can be termed fertile only when it contains all the materials requisite for the nutrition of plants in the required quantity and in the proper form.
(2) With every crop a portion of these ingredients is removed. A part of this portion is again added from the inexhaustible store of the atmosphere; another part, however, is lost for ever if not replaced by man.
(3) The fertility of the soil remains unchanged if all the ingredients of a crop are given back to the land. Such a restitution is effected by manure.
(4) The manure produced in the course of husbandry is not sufficient to permanently maintain the fertility of a farm; it lacks the constituents which are annually exported in the shape of grain, hay, milk, and live stock.
These laws of Liebig form the basis of modern scientific agriculture.
Liebig was the first to treat bones with "Schwefelsäure" or sulphuric acid in order to make the calcium phosphates soluble (superphosphate); and the late Sir John B. Lawes was the first to commence the manufacture of superphosphate on a large scale, both from bones and mineral phosphates.
From these early beginnings an enormous industry ​has been built up in every civilized country of the globe, but especially in England.
Liebig, like his own compatriot Heinrich Heine, could handle the weapon of satire with consummate skill, attacked England in the following words: "England is robbing all other countries of the conditions of their fertility. Already, in her eagerness for bones, she has turned up the battlefields of Leipzig and Waterloo, and of the Crimea; already from the catacombs of Sicily she has carried away the skeletons of many successive generations. Annually she removes from the shores of other countries to her own the manurial equivalent of three millions and a half of men, whom she takes from us the means of supporting, and squanders down her sewers to the sea. Like a vampire she hangs upon the neck of Europe, nay, of the entire world, and sucks the heartblood from nations without a thought of justice towards them, without a shadow of lasting advantage for herself."
His work revolutionized agriculture, and made a science of it. He says in his Familiar Letters on Chemistry that "chemistry leads man into the domain of those latent forces, whose power controls the whole material world, and on whose operation is dependent the production of the most important necessaries of life and society. … No science like chemistry offers to man such a multitude of subjects for thought and reflection, and such stores ​of knowledge imbued with the charms of never-ending freshness; none is more calculated to awaken the talent for observation, or to sharpen the intellect in the strict method of applying proof for the establishment of a truth, or in the inquiry into the cause and effect of a phenomenon."
Concerning his great labours in the domain of agriculture, he says: "Does not chemistry promise that instead of seven grains we shall be enabled to raise eight or more on the same soil?"
Great men work not only by their deeds, but also by their personal lives. Liebig laboured by the influence of his own example to destroy a prejudice which restrained most agriculturalists from devoting themselves to the study of scientific farming.
In 1845 the Grand Duke of Hesse-Darmstadt conferred upon him the title of baron, and in 1852, as already stated, he was appointed to the chair of chemistry in the University of Munich.
His researches were not only confined to scientific agriculture, but physiology, pathology, and organic chemistry owe much to his indefatigability. His influence in chemistry was great—being one of the world's most famous chemists—and to his numerous pupils he was their "guide, philosopher, and friend." He satirized the work of other leading men, as the following remark bears evidence. In 1867 Liebig being asked by Dumas ​why he had abandoned organic chemistry, replied that "now, with the theory of substitution as a foundation, the edifice may be built up by workmen: masters are no longer needed."
Although he had his own views on most subjects, he was always open to correction. He said: "In the history of the evolution of any science, the researches of a given period of time furnish certain general relations which every moment are changed and improved upon by new discoveries. Thus an endeavour arises to arrange the new-discovered facts and to find the common bond by which they are linked together."
Liebig's definition of a compound radicle holds good to this day, although his definition of organic chemistry—as the study of the compound radicles—has been superseded by that of Schorlemmer, who defines organic chemistry as that branch of the science which treats of "the hydrocarbons and their derivatives."
Liebig predicted the organic ammonias, and discovered chloroform—the invaluable liquid which was first introduced into medicine by Sir James Simpson in 1848. He also discovered chloral and aldehyde. Liebig established the molecular formula of citric acid, and proved that it was tribasic; and in the year 1838 appeared his classical memoir on the constitution of organic acids, showing that the doctrine of basicity could be applied to them as well as to the acids of inorganic chemistry.
​It was Liebig who actually discovered bromine from the liquor of the salt works. He saturated the liquor with chlorine, and by distillation obtained a quantity of a dark red liquid. He thought it was the chloride of iodine, but did not examine it. It was on the shelf in his laboratory, and there it remained for several months. In 1826, Balard, of Montpellier, discovered bromine, and in Liebig's laboratory this very same bromine was labelled "liquid chloride of iodine." He was only twenty-three when the incident occurred, but he resolved in future never to take anything for granted, or to accept theories which were not well supported by trustworthy experiments.
Liebig was a man of untiring labour, always at work, early and late, and his discoveries and philosophy have proved of the highest importance to mankind. His mind was open to correction; he once said that "there is no harm in a man committing mistakes, but great harm indeed in his committing none, for he is sure not to have worked."
Liebig's books on Animal Chemistry (1842), Researches on the Chemistry of Food (1847), The Natural Laws of Husbandry (1862), etc., have been translated into most of the languages of Europe.
Liebig often visited England, and attended several meetings of the British Association. In 1837 he was requested by the Association to draw up a report on the ​progress of organic chemistry, which he did; and in the same year, speaking of radicles, he said that "in mineral chemistry the radicles are simple; in organic chemistry the radicles are compound—voilà toute la différence."
Liebig was not content to merely formulate generalizations and leave the details of work to others; he brought his philosophy down to the level of the average mind; and by inventing the extractum carnis Liebigis, or Liebig's Extract of Meat, he gave to the world an article of vast importance to the invalid and housewife.
He received most of the honours that are usually awarded to men of science, such as the Copley medal of the Royal Society, and the associateship of the Académie des Sciences (l'Institut de France). He will ever be remembered for his work in agricultural chemistry and combustion analysis, both of which are unique in the annals of chemistry.
Two years after the Franco-Prussian War and the reconstitution of the German Empire, Baron Justus von Liebig died on 18th April 1873, at the age of sixty-nine years, leaving the products of his genius to aid the progress of humanity.
He was "honoured and respected by every student of science, and loved by each of the band of ardent natures whom he had trained and set forth to battle for the good of their race." As a teacher he was unsurpassed, and a brave array of great thinkers sprang up as if by magic, ​due to his great enthusiasm and influence on the minds of men.
Lives of great men all remind us We can make our lives sublime, And, departing, leave behind us Footprints on the sands of time. Longfellow
Concerning Liebig's great power as a teacher, we may say with Cicero: "Quod munus reipublicæ afferre majus meliusve possumus quam si docemus atque erudimus juventutem."