In the Beginning
In order to understand the problem which Mendeleyev was attempting to solve, it is necessary to go back to the very origin of scientific thought.
Greece. The first appearance of genuine scientific thinking is traditionally credited to Thales, who lived in the sixth century BC in the Greek city of Miletus on the shore of Ionia.
Well over a millennium beforehand both the Babylonians and the ancient Egyptians had developed superior civilizations capable of highly advanced thought. Advanced observation and measurement had been the domain of the priestly castes in both Babylon and Egypt. These technical abilities, and any theoretical speculation they provoked, were a part of religious practice.
When the first stirring of scientific curiosity took place in ancient Greece, it was not linked to any religion.
Thales’ thinking was scientific because it could provide evidence for its conclusions. And it was philosophy because it used reason to reach these conclusions: there was no appeal to the gods or mysterious metaphysical forces.
Curiously, this was not the only major step in the evolution of human thought which took place during the sixth century BC. Quite independently, in other parts of the globe, humanity was taking several major steps which would affect the entire course of its development. China witnessed the arrival of Confucius and Lao-Tzu (the founder of Taoism, the rival of Confucianism), Buddha began preaching in India, and in Persia the fire-worshipper Zarathustra founded Zoroastrianism (which was to have a major influence on both Judaism and Islam).
By the end of the century Pythagoras was living at the other end of the Greek world in southern Italy.
The direction of both Eastern and Western civilizations was set by events which took place during the sixth century BC. The most important, for the Western world, was certainly the development attributed to Thales of Miletus, the first philosopher-scientist. His theory that the world had developed from one element (water) was just the beginning. This idea, once conceived, was quickly developed by Thales’ pupils in Miletus – the philosophers known as the Milesian school. One of these was Anaximenes. Anaximenes argued that the fundamental element wasn’t water, it was air.
In 494 BC the Persian army overran Miletus. By the fall of Miletus, philosophy had already spread from the Ionian coastline to the Aegean islands, and thence to the rest of the Greek world.
Heraclitus was born around 540 BC, and was an arrogant, misanthropic man. Heraclitus had his own idea about the fundamental element from which the world was formed. According to him, this was fire. Heraclitus’ ever-changing fire uncannily resembles the notion of energy in modern physics.
The ultimate element had now been seen as water, as air and as fire. So, which was it? There seemed an obvious answer to this question. Why should there be just one? Why not several? Why not all three of them – with an added fourth element to account for the world’s solidity?
The clear answer seemed to be that the world was in fact made of four fundamental elements: earth, air, fire and water. The four-element theory was put forward by Empedocles, who lived in a Greek colony in Sicily during the fifth century BC. He claimed that nothing in the world was created or destroyed – and maintained that all things consisted of differing combinations of the four elements. Here, for the first time, are the shadowy beginnings of the idea of chemistry.
The first individual chemist known to history was ‘Tapputi, the perfume-maker’, who was mentioned on a cuneiform tablet from the second millennium BC in Mesopotamia.
Practice long preceded theory. By the Hellenic era the ancient world had also discovered over half a dozen metallic elements, and a couple of non-metallic ones.
The ancients knew of these elements, but they didn’t know them as such. They had no idea that they were elements. Such a thing remained beyond their conception. The notion of an element originated with the philosophers, not the chemists. In other words, with the thinkers, not the practitioners.
Greeks. It was the fifth – century philosopher Leucippus who asked the question: ‘Is matter discrete or continuous?’ In other words, is it possible to go on dividing things up indefinitely, or does one reach a point where things become indivisible? Leucippus considered it self-evident that the latter was the case. This led him to the idea of the atomos, or atom. In Greek this word means ‘uncuttable’, i.e. indivisible. Leucippus was the first to state that the world was made up of indivisible atoms.
His best-known pupil was Democritus, who was to develop Leucippus’ original atomic idea. During the lifetime of Democritus, Greek philosophy entered its golden era, in Athens.
Ironically this golden era, which remains unrivalled in the entire history of philosophy, was to be very much a reaction against the achievements of Democritus, Empedocles, Heraclitus and their like. The first great Athenian philosopher was Socrates, who was born around 477 BC and was sentenced to death in 399 BC. Analysis is always necessary to clarify meaning – but the way Socrates used it, this method tended to take knowledge apart rather than build it up.
Socrates was succeeded by his great pupil Plato. Instead of scientific speculation, philosophy now turned its attention to abstract ideas. Abstract reasoning, abstract ideas, abstract geometry – even Plato’s political teaching concentrated on the idea of a utopia rather than on social reality. Democritus had arrived at the concept of the atom by applying mathematics to nature. Plato was only interested in applying mathematics to itself.
The third of the Greek triumvirate of great philosophers was Aristotle, who was a pupil of Plato. Aristotle was to make major contributions in almost every field except mathematics. Aristotle’s achievements mapped out the course of scientific development until well into the modern era. Aristotle turned Plato’s philosophy on its head, believing that ideas could exist only in the particular substance that embodied them. He saw objects as possessed of qualities – the Platonic ideas which inhabited them – rather than actual properties. Aristotle worked out that each of the four elements had its place. Earth was in the centre, next came water, above that was air and above the air came fire. But the sun, the moon and the stars clearly did not move in such a way, so Aristotle proposed a fifth element. This rarefied element he called aether. The heavens, from the moon upwards, were all part of this aethereal realm.
The idea that the world consisted of earth, air, fire and water belonged in the past. And no amount of brilliant thinking could save any science based upon such a premise. The investigation of the elements would now be approached from an entirely different direction – one which was both unscientific and irrational. The science of the elements now passed into a darker realm.
The Practice of Alchemy
Alchemy is traditionally said to have begun in Alexandria. This city was founded at the mouths of the Nile in 331 BC by Alexander the Great as his capital of the conquered territories of Egypt.
The library established Alexandria as arguably the greatest centre of learning in ancient times, superseding even the Athens of Plato and Aristotle. The major intellectual figures of the Hellenistic era, such as Euclid, Archimedes and Aristarchus (the Copernicus of antiquity) studied there – as, later, did the astronomer Ptolemy and the first great woman mathematician-philosopher, Hypatia.
But in Alexandria Greek thought encountered a much older form of learning, known as the Egyptian art, or khemeia (the root of our word chemistry). Initially this knowledge consisted largely of the chemical processes involved in embalming the dead. Khemeia thus became connected with the seven known metallic elements: gold, silver, copper, iron, tin, lead and mercury.
But it was when the Greek philosophical tradition encountered khemeia that alchemy was truly born. Once khemeia adopted earth, air, fire and water as the four elements, it was soon recognized that these were not fixed elements. They were qualities – analogous to hot and cold, wet and dry. But qualities could be changed. Hot could be turned into cold, wet into dry and so forth. A central aspiration of alchemy now emerged. Neither spiritual wisdom nor chemical technique was sought – the aim was pure gold. There appeared to be no hope for science here.
The earliest known adept of the dark arts was a certain Bolos of Mendes, a Hellenized Egyptian who lived around 200 BC.
Zosimos of Panopolis, acknowledged as the greatest of the early alchemists, who practised in Alexandria around AD 300. Zosimos compiled an encyclopedia of alchemy in twenty-eight volumes, one for each letter of the Greek alphabet. At one point Zosimos defines alchemy as the study of ‘ the composition of waters, movement, growth, embodying and disembodying, drawing the spirits from bodies and bonding the spirits within bodies’. Most interesting of all, Zosimos appears to have understood that chemical change can be induced by the presence of a catalyst.
From avarice, to medicine, to salvation: thesis, antithesis, synthesis – alchemy’s evolution followed its wayward dialectic course. And then, being only human, returned to where it had started from: gold!
By the early centuries AD recognizable alchemical practices were well established in South and Central America, China and India.
Alchemy formed a universal stage of human evolution, a necessary stepping-stone in our intellectual development.
Western alchemy, for instance, always remained obsessed with making gold. Chinese alchemy, on the other hand, concentrated more on medicine and salvation, developing a blend of these two aspects in the search for immortality.
It is easy for us to mock at the aims which inspired alchemy in its development: untold riches, panaceas, immortality, etc. Yet this is the practice which was to give us chemistry.
Diocletian’s edict contains the first official mention of the word khemeia. Diocletian had banned alchemy because he thought it would be successful. He was afraid that the widespread production of gold would undermine the empire’s tottering economy.
Curiously it was a Christian sect, the Nestorians, which seems to have carried the secrets of alchemy to its next destination. A number of Nestorians had continued with the clandestine practice of alchemy, and they took with them the secrets of the dark art. These eventually passed on to the Zoroastrians, who were intrigued by the mysterious manifestations of fire in alchemical theory and practice.
In 529 the Christian Emperor Justinian closed down the nine-centuries-old Academy of Plato in Athens, declaring it to be a centre of ‘pagan learning’. This date is traditionally recognized as the beginning of the period once evocatively known as the Dark Ages, which were to envelop Europe for the next five centuries.
For almost seven centuries, Europe would not produce an original scientist worthy of the name.
In 670 the Arab fleet even laid siege to Constantinople, the last remnant of the Roman Empire and the centre of Christendom. Surrender was only a matter of time. The Arabs could then strike across southern Europe to meet up in a pincer movement with their compatriots who were advancing to Spain, and would eventually spill over the Pyrenees as far as Tours in central France. Europe was set to become a Muslim continent. This plan was thwarted by an alchemist called Callinicus. Probably born in Egypt of Greek parentage, Callinicus had fled before the advancing Arabs, carrying with him the secret formula for ‘Greek fire’.
The Arabs were suitably impressed by this example of Greek learning, and soon began discovering other examples of this ancient knowledge in Syria and Mesopotamia. From the Nestorians in Baghdad they learned the art of khemeia, which they soon called al-chemia. (The prefix al is Arabic for ‘the’.) Alcohol, alkali, algebra and algorithm are all Arabic in origin. For the next five hundred years the history of chemistry, and that of most other sciences (including mathematics), was to remain almost entirely in Arab hands. The central core of Arabic alchemy appears to have been based on The Emerald Tablet, a work written by the legendary Hermes Trismegistos.
The first exceptional figure to emerge in the field of alchemy was Jabir ibn-Hayyan, later known in Europe as ‘Geber’.
The Koran positively encouraged medicine and the study of scientific and mathematical learning. This was the way to gain insight into the will of God.
Jabir modified Aristotle’s doctrine of the four elements, especially in regard to metals. According to Jabir, metals were formed out of two elements: sulphur and mercury. Sulphur (‘the stone which burns’) was characterized by the principle of combustibility. Mercury contained the idealized principle of metallic properties. Jabir felt sure that this process required a catalyst. This became in Arabic al-iksir (elixir).
The Arabs were approaching an understanding of chemistry and what it could do. Yet Arab alchemists remained principally interested in the pursuit of gold. This quest was to inspire the second great alchemist of the Arabic world, Al-Razi (later known in Europe as Rhazes). Al-Razi was in fact a Persian who flourished in Baghdad during the early decades of the tenth century.
Al-Razi’s forte, and much of his originality, lay in classification. At a certain stage every science requires a genius of classification, to enable it to be compartmentalized into various fields, so that these can advance in their own separate manner.
Half a century after the death of Al-Razi came the greatest Muslim intellectual of them all – known to us as Avicenna, but in Arabic ibn Sina. Avicenna was born in 980 near Samarkand, the son of a Persian tax collector. In his scientific writings Avicenna proposed that a body stays in the same place, or continues moving at the same speed in a straight line, unless it is acted upon by an external force. Here is the first law of motion, set down six hundred years before Newton. In medicine Avicenna was the most important physician between Galen, the supreme medical mind of the Roman era, and Harvey, who was to discover the circulation of the blood in the seventeenth century. Avicenna died in 1037, probably of poisoning.
A copy of his pharmacopoeia was found as far afield as the great library at Toledo, when the city was recaptured by the Spanish in 1095. But even before this its secrets had been smuggled to Europe by Constantine of Africa. One day he turned up mysteriously at the medical school in Salerno with a copy of Avicenna’s pharmacopoeia. After translating this work into indifferent Latin, he became a Christian monk at Monte Cassino, where he died in 1087. In the following centuries Avicenna’s pharmacopoeia was to become the most influential medical text in Europe – the forerunner of modern pharmacy.
Genius and Gibberish
As the Arabic empire fragmented and declined, its great contribution to science and mathematics came to an end.
It is often said that the Middle Ages contributed nothing to science. This is not true. Technological advances were few and unspectacular – but significant after their own fashion.
The medieval mind accepted the basic premise of science: causation. Everything that happened was the effect of a previous cause – such thinking had been inherited from Aristotle. And it was to be used by Thomas Aquinas, the epitome of medieval theologian-philosophers, as a proof of God’s existence.
Albertus Magnus was born around 1200 in southern Germany. He studied at Padua and went on to become the finest teacher of his age in Paris. Such was the state of learning in the early thirteenth century that one could aspire to ‘know everything’. Albertus not only took up this challenge, but also sought to extend human knowledge: in philosophy, in what we would call chemistry, and in biology – as well as in the field of alchemy.
Albertus Magnus seems to have lived easily within the constraints of Aristotelianism. His great scientific contemporary Roger Bacon did not. Roger Bacon was born c. 1214; he became a Franciscan monk and studied at Oxford and Paris, where he also taught. Bacon’s ideas bear a remarkable resemblance to many of those which Leonardo da Vinci sketched in his notebooks – though they pre-date Leonardo by two hundred years, and in many instances go beyond him. Despite his exceptional scientific vision Bacon remained convinced of the basic premise of alchemy: the possibility of transmuting base metal into gold. Here he succumbed to Aristotelian notions.
Like astrology, alchemy was a wrong turning in human knowledge, a mistake. Yet astrology enabled us to analyse and delineate specific elements of personality, helping us to think about who we are, long before the advent of psychology as a science. Similarly alchemy enabled us to ask – and go on asking – about the material world, to question what precisely it is.
In 1204 the French soldiers of the Fourth Crusade overran Constantinople, deposing the emperor. During the consequent pillaging, countless ancient Greek and Byzantine manuscripts were lost – including a vast heritage of alchemical lore.
So instead of slavishly attempting to decipher ancient esoteric texts, the thirteenth-century alchemists were now inspired to undertake their own original endeavours.
The elixir of the Arabs now became transformed into the ‘philosophers’ stone’. Like the unicorn, the philosophers’ stone had all manner of striking qualities – except existence. Without it, chemistry would not be what it is today. In order to discover that no such thing as the philosophers’ stone existed, it was necessary to ransack and analyse every substance known on earth.
History is not what actually took place, but what we believe took place. Despite widespread charlatanry there is no doubt that many alchemists of this period were honest in their endeavours. In their ravening search for the philosophers’ stone the fourteenth century alchemists became the first to understand the nature of acids.
Just after 1300 the False Geber discovered vitriol, better known to us as sulphuric acid. Besides sulphuric acid, False Geber also described how to make strong nitric acid – which was called aqua fortis, literally ‘strong water’, because of its ability to dissolve almost anything except gold.
In order to generate some much-needed income, alchemists soon began prescribing different elixirs for different medical complaints.
The elixirs produced by the European alchemists reinforced this idea. Pharmacy was being born in Europe.
Such practice was aided by the discovery of the most important elixir of all time. It was produced by the careful distillation of wine. The alchemist who first produced almost pure alcohol was Arnold of Villanova, born in Spain in the fourteenth century. Like aqua fortis (nitric acid), aqua vitae (alcohol) was found to be a solvent, though of a different, more subtle tenor. In French it became eaudevie, in Scandinavian languages akvavit, in Gaelic usquebaugh (whisky).
Meanwhile alchemy itself continued to come up with little more than fool’s gold. Not surprisingly, the dark art now entered a third period of decline – the previous ones being at the end of the Roman Empire and the break-up of the Arab Empire. Once again, alchemy was officially banned: this time by Pope John XXII in 1317.
The Emerald Tablet, written by the mysterious Hermes Trismegistos. This work, which was probably written in Alexandria around the first century AD and had later become central to Arabic alchemy, probably began to circulate in Europe sometime in the fifteenth century. It is believed to have been one of the many ancient books brought to the West by Greek scholars fleeing Constantinople some time before the capital of the Byzantine Empire fell to the Ottoman Turks in 1453.
When Copernicus translated this idea into scientific fact, announcing that the earth and the planets orbit the sun, his inspiration was not entirely scientific. In his De Revolutionibus Orbium Coelestium (‘On the Revolutions of the Celestial Spheres’), he specifically mentions Hermes Trismegistos, using him as an authority to back up his revolutionary idea.
Science was entering a new era of discovery which would change forever the way we view the world.
Paracelsus
Theophrastus Bombast von Hohenheim, better known to history as Paracelsus, was born in the Swiss village of Einsiedeln late in 1493.
Paracelsus’ early experience with his father made him highly expert in both the properties and the handling of minerals. This expertise was extended when he began working, perhaps as an apprentice overseer, in the local mines and workshops owned by Sigismund Fugger, who was also a keen alchemist.
The Fugger family had mining interests from Hungary to Spain, and a network of banking agents extending from Iceland to the Levant.
He visited to Constantinople in 1522. It was here in Constantinople that Paracelsus rediscovered some of the lost secrets of Byzantine alchemy, bringing them to Europe for the first time. He also picked up some equally sensational genuine scientific knowledge.
Later, Paracelsus was the first European physician to state that, when introduced into the body in small doses, ‘what makes a man ill also cures him’.
In effect, chemistry was of course still alchemy. But Paracelsus roundly declared that alchemy was wasting its time in trying to produce gold. The techniques of alchemy should be put at the service of medicine – to produce chemical cures for sickness and diseases, specific medicines being prepared for the treatment of specific diseases. Medicine would then become a science, rather than the faintly dubious art which it then appeared to be.
Paracelsus’ view of the elements was a variant on traditional ideas. He accepted Aristotle’s earth, air, fire and water. He also accepted the Arabic development of the three principles: sulphur (giving flammability or combustion), mercury (giving volatility and its opposite) and salt (giving solidity).
In 1527 Paracelsus turned up in Basel. Here an influential local figure called Johan Frobenius summoned him as a last resort to treat his disabled right leg. At the time when Paracelsus was treating Frobenius, the Dutch Renaissance scholar Erasmus happened to be staying in his house. Erasmus was a man of vast learning, who prided himself on the independence of his outlook. Aware of his own shortcomings, it was he who coined the phrase: ‘In the country of the blind, the one-eyed man is king.’
The orthodox medicine of the day operated according to the theory of the ‘four humours’, which derived from Hippocrates. These were blood, phlegm, choler (yellow bile) and melancholy (black bile). The balance of these humours in the body governed its physical and mental qualities. Each humour had its seat in one of the major organs: the heart (blood), the brain (phlegm), the liver (choler) and the spleen (melancholy).
But Paracelsus would have none of it. Humanity had to be released from this cage of metaphysical symbolism and set free into the open air of actuality.
Paracelsus was probably first to realize that zinc was metallic. He also discovered a method for isolating metallic arsenic, mixing the sulphide with eggshells and describing the resultant metal as ‘white like silver’ – although Albertus Magnus probably preceded him in the actual isolation of this element.
Chemistry was not yet a coherent science, more a growing proliferation of techniques. But it was becoming evident that something was emerging from the alchemical hell’s kitchens: a subject that was distinctly separate from the quest for gold. It has been claimed that Paracelsus was the first to refer to this subject as chemistry.
For the first time in around two millennia new elements were beginning to be found.
On the night of 21 September 1541 Paracelsus is said to have suffered a heavy fall on his way back to the White Horse Inn. Paracelsus died three days later on 24 September.
Less than two years later Copernicus published his work placing the sun at the centre of the planetary system, and the scientific revolution began.
Trial and Error
The generally held picture of the medieval age as all but incapable of genuine scientific advance is not entirely accurate.
In an age which had practically no notion of experiment beyond the realms of the alchemist’s den, Dietrich von Freiberg conceived of an experiment whose originality and perception is breathtaking. How could he study what caused a rainbow?
By means of this experiment he was able to produce theoretical explanations of how the rainbow produces its different colours, why it forms an arc, why the primary rainbow frequently has a second fainter upper arc, and why two people standing side by side do not in fact see the same rainbow.
Nicholas of Cusa was born in 1401, the son of a moderately prosperous Rhineland fisherman. He quickly revealed an exceptional mind, but first came to public attention after conducting research into the Donation of Constantine. This was the fourth-century document in which the Emperor Constantine had allegedly ceded domination of the Byzantine and Roman Churches to the Pope. It was widely regarded as the final evidence for the Pope’s claim to supremacy. Nicholas of Cusa showed that this document was in fact a forgery, dating from the eighth century.
Nicholas of Cusa introduced the idea that applied maths was the way to know the world. This brings practical knowledge. ‘Mind alone counts; if mind is removed, distinct numbers do not exist.’ Measurement, the matching of discrete parts of the world to numerical quantities – here lay the key.
Nicholas of Cusa’s philosophical-scientific ideas may have been exceptionally advanced, but his actual scientific ideas were explosive. He believed that the earth revolved on its axis, and this led him to conclude that it moved around the sun. He also worked out that the stars were just like our sun, and they too must be circled by inhabited worlds. Further speculation led him to conclude that the universe was infinite. And since it had no central point, there was in space no such thing as ‘up’ or ‘down’. Some of these ideas would remain ahead of their time until the dawn of the twentieth century.
Nicholas of Cusa’s ideas passed virtually unnoticed for so long. Even Copernicus had not heard of them when he worked out in mathematical detail the heliocentric plan of the solar system which Nicholas of Cusa had surmised. Where Nicholas of Cusa had a hunch – as did several of the ancient Greeks – Copernicus produced a scientific model based on detailed observations, with mathematical backing.
Every revolution needs its propagandist, and Giordano Bruno was to take on this role for the Copernican revolution. Bruno was born in 1548 in the small town of Nola, some 20 km east of Naples. He read and absorbed the views of Erasmus (who was forbidden) and Paracelsus (who was ridiculed), and was not afraid of defending his views in passionate fashion. Bruno seems to have read many of Nicholas’ major works during this period.
Bruno’s cosmological views are almost identical to Nicholas of Cusa’s, but his manner of expressing them reflects the change in world-view which was gradually taking place.
Some time while he was at Naples, Bruno came across the works of Hermes Trismegistos, the legendary ‘Egyptian’ alchemist. Hermes Trismegistos spoke of ancient Egyptian knowledge. This was the prisca theologia, the pristine (or pure) theology which had inspired all others.
Bruno impetuously went one further than this. Secretly he believed that the Renaissance had only partly begun. The true Renaissance was yet to come. This would see the rebirth of the prisca theologia, where Christianity would be surpassed by the original true religion of history, the pure theology of Ancient Egypt, as featured in the writings of the mythic magus Hermes Trismegistos.
Our mind, our language, our ideas, even our inspiration – these are all prompted by the past, the previous, the apparently discarded. Such things seem to play a left-handed role in the very thought which has overcome them. A prime example of this remains the role of alchemy during the ensuing century.
Once again Bruno stands at the pivotal point. Mysticism and alchemy led him to develop a successful and practical mnemonic system. A century later, the details of this system would be studied by Leibniz, the German rationalist philosopher – inspiring him to construct one of the first calculating machines, consisting of a system of concentric wheels.
But Bruno’s memory system was to have further, even more extensive ramifications. Besides being allied to Lully’s alchemical system, it was also closely connected to a similarly far-reaching method of thinking which Bruno himself developed. This method was to play a major role in his thought, and marks the inception of a significant development in European thinking. Bruno saw his new method of systematic thought as a form of creative logic: a way of thinking which would generate new knowledge. This had its origins in Nicholas of Cusa’s coincidentia oppositorium – the method of viewing things by which opposites eventually came together.
Just over two centuries later the German philosopher Hegel would discern in this statement the seeds of his own great dialectical method. As with Bruno’s method, Hegel’s dialectic involved two opposites coming together to generate something else.
At the same time as Bruno was lecturing in Toulouse the Portuguese philosopher Francisco Sanches was in residence and writing Quod Nihil Scitur (‘Why Nothing Can be Known’). This all but forgotten masterpiece of profound philosophical scepticism argues that we can never really know the truth.
This very same idea was to be the starting point for Descartes – the thinker who sparked the seventeenth – century philosophical renaissance. Nicholas of Cusa’s identity of opposites, Bruno’s pre-dialectical system of thought, Sanches’ methodic doubt – new ways of thinking were beginning to emerge, attempts to break out of the stranglehold of Aristotelian logic and doctrine.
After Nicholas of Cusa, Lucretius was to be the main influence on Bruno’s scientific thought, although Lucretius and Nicholas of Cusa are opposites in all but their science.
The Elements of Science
In the most literal sense, an entirely new way of seeing the world was discovered in 1608. The invention of the telescope is usually credited to the Dutch lens-maker Hans Lippershey, who sold his lenses as spectacles. Lippershey himself didn’t actually discover the telescopic effect; this was the work of an anonymous apprentice. He noticed that when he placed two lenses before his eyes, and adjusted the distance between them, he could form a magnified image of a church tower across the fields. Lippershey immediately realized the importance of this serendipitous perception, mounted the two lenses in a tube and named this invention the ‘perspicillium’ (meaning ‘an instrument for looking through’.)
Within the year it had reached the ears of Galileo in Padua. It was Galileo who would first promulgate the elements of the new science. By the end of the sixteenth century, Padua was widely regarded as the finest university in Europe, attracting students from as far afield as Poland and England.
The first perspicillia were only capable of up to threefold magnification. Within months Galileo had perfected an instrument capable of tenfold magnification.
Around fifteen hundred years earlier a few isolated Greek thinkers, particularly Archimedes, had produced various unrelated mechanical facts and theorems – but there was no overall conception of mechanics as such. It took Galileo, who came up with the central notion of ‘force’, to show that here was an entire branch of unified theoretical and practical learning to be investigated.
Galileo became the pioneer explorer in this new field of learning, which he called meccaniche (or mechanics, from the ancient Greek for ‘a contrivance or machine’.)
Only when Galileo combined mathematics and physics was it possible to conceive of the notion of measurable force. And with that modern science was born. Applying mathematical analysis to the problems of physics gave rise to experimental science in the modern sense.
Galileo was not always the first to arrive at an idea (even when he genuinely thought he was), but his was usually the finest mind to do so.
When Galileo trained his telescope on the night sky, the entire structure of the universe changed before his eyes. Things could never be the same again. Galileo was the first truly original philosopher of science since Aristotle.
Galileo restricted science to the question: ‘What happens?’ He ignored science’s concomitant question: ‘What is it?’ Physics can operate without the latter question, but it is a central perception of chemistry. However, by this stage the vision of chemistry had become hopelessly blurred. Arguably, its only significant use was the manufacture of medicines.
The ageing, ailing Galileo may have escaped burning at the stake, but he was nonetheless sentenced to life imprisonment – which in practice became house arrest at his home outside Florence. The shock waves quickly spread throughout Europe. In Holland, the French philosopher René Descartes was putting the finishing touches to his Treatise on the Universe, in which he had independently come to many of the same conclusions as Galileo.
Descartes’ approach was different from Galileo’s experimentalism. For the French philosopher, the prime tool in the quest for knowledge was reason. To achieve a clear scientific view of the world, nothing less than an entirely new method of thinking was required. Nothing remains certain. But in the midst of all this there is nevertheless one thing which does remain certain. No matter how deluded I may be in my thoughts about myself and the world, I still know that I am thinking. This alone proves to me my existence. In the most famous remark in philosophy, Descartes concludes: ‘Cogito ergo sum’ – ‘I think, therefore I am.’ Descartes was a superb original mathematician. So it is perhaps not surprising that Descartes’ all-embracing scientific vision bears a strong resemblance to mathematics.
Where Galileo sought a method of experiment, Descartes sought a method of thought. The first he defines as ‘the conception, without doubt, of an unclouded and attentive mind, which is formed by the light of reason alone’. Deduction was defined as ‘necessary inference from other facts which are known for certain’. Descartes’ celebrated method – which came to be known as Cartesian method – lay in the correct application of these two rules of thought.
Both Galileo and Descartes viewed the world as mechanical. Galileo conceived of the notion of force, and created mechanics. Descartes attempted to explain the entire world in terms of a ‘mechanical philosophy’. Galileo sought to lay down experimental guidelines; Descartes sought to develop a mathematical-mechanical philosophy.
Meanwhile one man was already producing a science of thought and practice which combined, and even superseded, these attempts. The pioneer responsible for this was the Englishman Francis Bacon. Francis Bacon was born in 1561.
His major work of scientific philosophy, the Novum Organum, was written while he was lord chancellor. The title refers directly to Aristotle’s Organon, the work in which he outlined how knowledge was arrived at by logical deduction. Bacon’s aim was no less than to establish an entirely new method of arriving at knowledge. It would supersede the Aristotelian method, which had held good for two millennia, and for the first time establish a firm foundation for the advance of scientific knowledge. Previously science had been characterized by two approaches. Those who have handled science have been either men of experiment or men of dogmas. To elaborate: the first method was followed by the ‘empirics’, who simply built up a jumbled body of unrelated facts. (For Bacon alchemy fell into this category.) The second, the Aristotelian approach, was more systematic but equally misguided.
Bacon was convinced that scientific knowledge could move only in the opposite direction – from particular instances to general principles. Particular instances are tested in experiments, and from these a general theory can be formed.
Bacon maintained that science could build up a body of knowledge only by inductive logic.
Aristotle had pointed out fallacies in deductive logic. Bacon showed that inductive logic could likewise fall prey to ‘false notions’ and ‘prejudices’. These ‘idols of the mind’, as he called them, came in four distinct categories. ‘The Idols of the Tribe have their foundation in human nature itself . . . human understanding is like a false mirror, which, receiving rays irregularly, distorts and discolours the nature of things by mingling its own nature with it.’
‘The Idols of the Cave are the idols of the individual.’ These are the prejudices and intellectual peculiarities which result from our particular upbringing, education and experience.
Idols of the Market Place result from our interaction with others, where ‘the ill and unfit choice of words wonderfully obstructs the understanding’.
Bacon’s fourth false notion he named ‘Idols of the Theatre’. These consisted of ‘the various dogmas of philosophies’.
Bacon well understood that deductive reason could work only if properly applied. It was no good making premature generalizations from just a few cases.
There were now several experimenters of the highest order working in England. Amongst these was the physician and physicist William Gilbert. Two centuries before Faraday, Gilbert had an inkling of the great hidden role electromagnetic forces played in the world. With hindsight, we can see that Newton’s momentous idea of gravity, which he produced half a century later, was in a certain way an extension of this simple unverified suggestion floated by Gilbert.
Sir William Harvey, who discovered the circulation of the blood, was for a while Bacon’s personal physician. Where Copernicus started the scientific revolution, Bacon set out the mental revolution which would have to accompany it.
‘If a man will begin with certainties, he shall end in doubts; but if he will be content to begin with doubts, he shall end in certainties.’
Solomon House was to be the inspiration for the founders of the Royal Society, which , during the following century under the presidency of Newton, would become the leading scientific institution in Europe.
A Born-again Science
The Flemish physician Jan Baptista van Helmont was born in 1577. Although guided by mystical ideas, for the most part van Helmont did not allow them to interfere with his scientific approach to his experiments. Van Helmont abandoned Paracelsus’ idea of three elements (mercury, sulphur and salt), rejected the Aristotelian four-element theory from which it had been derived, and went back to the very origins of elemental theory. Van Helmont believed that his experiment with the willow proved that ultimately everything was made of water, the conclusion Thales had reached over two millennia earlier. Van Helmont’s experiment is widely regarded as the first application of measurement to an experiment involving both chemistry and biology, marking the inception of biochemistry.
According to ancient Greek mythology, the cosmos (‘order’) had originally been created out of a similar unshaped, unordered substance called chaos – so van Helmont decided to call these vapours or air-like substances ‘chaos’. In Flemish the first consonant of this word is pronounced in a heavy guttural manner, and this is the origin of the word ‘gas’. Distinct fundamental principles regarding the nature of matter were now beginning to emerge. First there had been liquids and solids, now there were gases. He discovered that certain metals could be dissolved in various strong waters (acids). It was even possible to recover from this solution exactly the same weight of metal as had been dissolved into it. This led van Helmont to an understanding of the fundamental property of matter. Despite its transformation during experiments, matter was never destroyed.
Van Helmont’s pioneering biochemical work also led him to investigate human digestion. He concluded that ‘hungry acid’ in the stomach reacted with the food, Van Helmont was on the brink of a vital discovery here, but this would only be made some years later by his pupil Franciscus Sylvius, who in 1658 became professor of medicine at Leyden, by then one of the leading universities in Europe.
Sylvius saw digestion as a ’natural’ chemical process, involving acid saliva, alkaline bile and the recently discovered pancreatic juices, which by reaction and taste were deemed to be acid. Sylvius extended the boundaries of chemical understanding. He recognized that many naturally occurring salts resulted from the reaction between acids and alkalis. Sylvius’ work was then carried a step further by his pupil, the obscure German apothecary Tachenius.
Tachenius felt certain that acid and alkali were the two principles which subsumed all chemical reactions. The acid-alkali distinction held the key to a science of practical chemistry.
Evangelista Torricelli had discovered air pressure. He had invented the world’s first barometer, for measuring air pressure. Three centuries before the first rockets were fired into space, it was known that the earth’s atmosphere extended only a certain finite distance from its surface. Arguably, Torricelli’s experiment had led to the discovery of space itself.
It was now clear that gases were exactly the same as solids and liquids. Like them, gases had weight. They were just much more diffuse (or less condensed). Gases too were a form of matter.
The German engineer and inventor Otto von Guericke. The big philosophic topic of the day was the nature of a vacuum. Could such a thing exist? According to Aristotle, it could not, and this had been accepted as ‘authority’ by later philosophers, who gave us the saying, ‘Nature abhors a vacuum.’ Guericke decided to settle this question by experiment. Guericke’s most famous performance was carried out on 8 May 1654 before the Emperor Ferdinand III, and attracted vast crowds from all over Saxony. This time his experiment involved two large hollow copper hemispheres, which had been precisely cast so that their rims fitted tightly into one another. (These were to become known as Magdeburg hemispheres.)
Considered by many as the founder of modern chemistry, Robert Boyle was born in 1627 in a remote castle in the south-west of Ireland. Boyle proved Galileo’s prediction that in a vacuum any two bodies would fall at precisely the same rate. In the absence of any air resistance, a feather fell at the same rate as a lump of lead, contrary to Aristotle’s assertion. Boyle concluded at this stage that air was like an elastic fluid with reactive particles floating in it.
Water vapour behaved like any other gas, which meant that it too consisted of particles separated by a void. If this was the case when water was a gas, then it would seem likely that it was also the case when water was a liquid, and even when it was solid ice. And if this was true of water, then possibly it was the case with all substances.
Without being fully aware of what he was doing, Boyle was preparing the ground for the reintroduction of atomic theory. Boyle’s masterpiece was The Sceptical Chymist, which was published in 1661. This is generally regarded as the beginning of the new chemistry. Around this time Boyle also initiated the practice of writing up his experiments in a clear and easily comprehensible manner, so that they could be understood, repeated and confirmed by other scientists. The Sceptical Chymist launches into an attack on the Aristotelian theory of the four elements, and also its Paracelsian derivative of three elements. Instead, Boyle asserts that elements are primary particles. In the words of his famous definition, what he meant by elements were ‘certain primitive and simple, or perfectly unmingled bodies; which not being made of any other bodies, or of one another, are the ingredients of which all those called perfectly mixed bodies are immediately compounded, and into which they are ultimately resolved’. Boyle then went on to make a further fundamental distinction. These elements could combine together in groups or clusters to form a compound. (This is the first occurrence of the notion which would develop into the modern idea of a molecule.)
Like Paracelsus, Bruno, van Helmont and so many other chemical pioneers before him, Boyle too caught the alchemy bug. For many years historians of science preferred to skate over this unpalatable fact, mentioning it only in passing – as if it was some unfortunate occupational hazard of chemists at this time. As indeed it was.
To the end, Boyle’s work remained of the highest order. His greatest contribution to the chemistry laboratory was his discovery of a method for distinguishing between acids and alkalis.
By the time Boyle died in 1691, at the age of sixty-four, Newton had already published the Principia, his revolutionary work on gravity.
The trouble was, Newton’s ground-breaking scientific vision of the world had set a new standard for science. Any scientific advances were expected to incorporate the mechanical rigour and mathematical exactitude of Newtonian physics. Yet Newton was dealing with the world of quantity, rather than the world of quality to which chemistry still belonged.
The path of alchemy led to lunacy – not only for chemistry. The elements which Boyle had defined would now have to be discovered in a strictly literal sense.
Things Never Seen Before
As we have seen, nine elements were already known to the ancients, and three new ones were discovered in the late Middle Ages. Yet it is of course only with hindsight that we can recognize these as elements. Their discoverers did not see them as such, because they didn’t know what an element was. It was only in 1661 that Boyle came up with his definition of an element as a substance which could not be broken down into simpler substances. Around eight years later the first new element was discovered by Hennig Brand in Hamburg, when he isolated phosphorus.
Hennig Brand was something of a rarity himself. He is variously dubbed as the last alchemist or the first chemist.
In 1623 the British government passed a Statute of Monopolies which decreed that ‘letters patent’ could be granted for a period of up to fourteen years covering ‘inventions of new manufactures’.
Meanwhile scientific Academies had sprung up in Europe. The Royal Society was pre-dated by the Accademia dei Lincei (Academy of the Lynxes) in Italy; later the Académie Royale des Sciences in Paris developed from the informal meetings attended by the likes of Descartes and Pascal; and Leibniz was instrumental in setting up the Berlin Academy.
The secret of how to produce phosphorus would eventually be purchased in 1737 by the Académie Royale des Sciences in Paris, which immediately made it available to all scientists. Half a century later the Swedish chemist Karl Scheele found that phosphorus was a constituent of bones, and discovered a simpler, less distasteful method of extraction.
This was perhaps the most exciting period of chemical exploration. Freed from the straitjacket of alchemy, eighteenth-century chemists were able to reach out and explore the possibilities of an entirely new science.
But the intrepid Scheele survived, enabling him to turn his attention to the elements. In 1770 he became the first chemist to produce the gaseous element chlorine. Only thirty years later did the English chemist Humphry Davy (inventor of the miner’s lamp) realize that this gas was an element. Indeed, it was Davy who first named it chlorine (from the Greek for ‘light green’), on account of its appearance.
Comparatively speaking, Sweden’s contribution to this period of the scientific revolution was the equal of any other country’s. The eighteenth century was to prove Sweden’s golden era.
it was Scheele’s discovery of ‘fire air’ that was his greatest achievement. This was oxygen. It was the element which held the key to the future of chemistry. Scheele first produced ‘fire air’ in 1772 by heating mercuric oxide, which readily gives up its oxygen and reverts to mercury.
In 1751 the Swedish mineralogist Axel Cronstedt succeeded in isolating from kupfernickel ore a metal which bore no resemblance to copper. It was hard, silvery-white and was attracted by a magnet – a property not known in any other substance but iron. Cronstedt contracted the old miners’ name, calling his discovery nickel.
Using the blowpipe, Cronstedt carried out a systematic study of minerals, classifying them according to their chemical contents and chemical properties, thus becoming the father of modern mineralogy (literally, the study of substances that are mined).
The other important element discovered during this period has one of the most picturesque histories of all the elements. In 1735 a French sailor walking along an estuary beach on the Pacific coast of Columbia came across some lumps of greyish clay the size and weight of cannon balls.
The metal’s original name, shortened to platina, was eventually altered by the English chemist Davy to platinum, to bring its feminine Latin name into agreement with those of other recently discovered metals such as barium and molybdenum. The idea of a feminine metal was evidently anathema to the Victorian English scientific establishment. This was to be the start of a distressing trend. All elements discovered since 1839, a couple of years after Queen Victoria’s accession to the British throne, have been given the Latin neuter ending-ium, or the Greek neuter-on in the case of the inert gases. This sexless nomenclature was even extended to curium, which was named after Madame Curie. The sole exception to this rule is the element astatine, which has a feminine ending and is derived from the Greek astatos, meaning ‘unstable’.
The Great Phlogiston Mystery
Chemistry was becoming full of possibilities. Its practitioners were now discovering an exciting range of new elements and compounds. This process was hastened by the development of new laboratory experiments.
Not until the latter half of the seventeenth century was a new explanation of fire proposed. The man who came up with the idea was one of the most remarkable frauds in the history of science. Johann Becher was born in 1635 in the little German town of Speyer, on the banks of the Rhine. Becher’s masterpiece, Physica Subterranea, was published in Vienna in 1667 (during the lull between the silk fiasco and the Danube sand project). In this he advances his own theory of the elements, which was to have a profound effect on the chemistry of the next hundred years. According to Becher all solid substances consist of three types of earth: terra fluida is the mercurial element, and the third element is terra pinguis (literally ‘fatty earth’). Becher’s Physica Subterranea circulated widely throughout Europe, and went through several editions. By 1703 its third edition was being prepared in Germany by Georg Stahl.
The role of terra pinguis had now been extended beyond Becher’s original conception, so Stahl renamed it ‘phlogiston’ – from the Greekphlogios, meaning ‘fiery’. Stahl’s phlogiston theory appeared to explain, in a fully scientific manner, several of the major mysteries of material transformation.
Hermann Boerhaave, the professor of medicine at Leyden. In 1732 Boerhaave achieved fame and fortune by producing the first reliable textbook of modern chemistry, Elementa Chemtae.
Stahl was inclined to explain phlogiston as an immaterial principle, like heat. It simply flowed from one substance to another (carried by the surrounding air).
This state of affairs would not change until chemists carried out a systematic examination of the gases which made up air. The initial results of this proved spectacular. One of the first chemists to investigate the gases of the air quickly succeeded in isolating ‘phlogiston’. This investigation was carried out by the English chemist Henry Cavendish.
Cavendish became intrigued by the gas which was produced when certain acids reacted with metals. This gas had earlier been isolated by Boyle, and more recently by Cavendish’s contemporary Joseph Priestley; but as Cavendish was the first to investigate its properties in a comprehensive scientific fashion, its discovery is usually associated with him. He pioneered the weighing of particular volumes of different gases in order to discover their different densities. Initially he did this by weighing a bladder of known capacity filled with different gases.
Around the same time (1784-5) this same experiment was also carried out by James Watt, the developer of the steam engine.
If ‘inflammable air’ had not been discovered by Cavendish (or Boyle, or whoever), it would sooner or later have been discovered by someone. Science could now be viewed as a cultural-historical phenomenon, rather than simply the creation of individual geniuses working alone.
But it was neither Cavendish nor Priestley nor Watt who was to give this newly discovered gas its modern name. This happened a decade later when the great French chemist Lavoisier called it ‘hydrogen’ (from the Greek hydro, ‘water’, and-gen, ‘generator, begetter, maker’.)
Cavendish left none of his millions to science. Contrary to popular belief, the Cavendish Laboratory at Cambridge, founded sixty-one years after his death in 1871, was in fact financed by a relative.
The first director of the Cavendish Laboratory, the great pioneer of electromagnetism James Maxwell, collected Cavendish’s unpublished papers and even re-created several of his electrical experiments. This showed that Cavendish had anticipated much of the work of the two great pioneers in the field, Faraday and Maxwell himself. (The second came a generation later with Rutherford’s ground-breaking research into the structure of the atom, and the third was the discovery of the structure of DNA by Crick and Watson in 1953. No other laboratory in the world has yet been able to match such achievements.)
Amongst the most influential leaders of the Unitarian movement was Joseph Priestley, one of the few contemporary scientists with whom Cavendish maintained a sporadic correspondence. Priestley was born in 1733, just two years after Cavendish. Priestley collected the gas and observed its properties. Priestley was a great believer in scientific openness, and when he visited Paris later in 1774, he passed on his discovery of ‘dephlogisticated air’ to the greatest chemist of the era, Antoine Lavoisier. This was to have a far-reaching effect on the history of chemistry.
Indeed, this is the reason why Priestley is still so often accredited with the discovery of oxygen, though it is now known that Scheele had in fact performed precisely the same experiment with mercury calx two years previously in Sweden. Priestley’s discovery may not have been strictly original (except for him), but it was he who passed it into the scientific domain, where it was to have great effect. Such allocation of priority is not without precedent. A similar course was to be adopted with regard to several original discoveries made by the nineteenth-century German mathematician Karl Gauss.
The Mystery Solved
When Priestley demonstrated his ‘dephlogisticated air’ to Lavoisier in Paris, Lavoisier immediately grasped the far-reaching significance of this discovery. Priestley may have been a superb experimentalist, but Lavoisier had the superior theoretical understanding of chemistry. As no other, he used his encyclopedic knowledge of chemistry to establish a scientific structure for this field.
Not for nothing has Lavoisier become known as the Newton of chemistry. Antoine Lavoisier was born in 1743, into a wealthy upper-middle-class family. Lavoisier adopted a modern approach to chemistry. This was epitomized by his belief in the balance (such scales were the most precise weighing apparatus available at the time). Chemistry was nothing to do with mysterious transformations: all change could be explained and could also be measured. At the same time, he felt that chemistry was being severely hampered by traditional theories which in fact explained nothing and even appeared to be preventing further breakthrough.
In 1770 Lavoisier resolved to put this apparent transformation of water into earth to an exhaustive test, under the strictest scientific conditions. The ‘earth’ had not come from the water, it had been extracted from the glass by the boiling water. The last possible evidence for the four-elements theory collapsed.
Two years later Lavoisier turned his attention to the vexed problem of combustion. He conducted an experiment heating lead in a sealed vessel containing a limited supply of air. He had shown that the metal in fact combined with a material substance which had weight, and that material substance consisted of a portion of the air.
It was now that Priestley arrived in Paris, and demonstrated to Lavoisier the new elemental gas he had discovered, which he called ‘dephlogisticated air’. Lavoisier regarded this Nonconformist English minister as little more than an amateur, a well-meaning fellow of admirable liberal principles, but hardly a scientist of the first rank. Like so many Englishmen he was a pragmatist, rather than a man of reason – no match for a French theorist.
As soon as Priestley returned to England, Lavoisier repeated Priestley’s experiment and obtained so-called ‘dephlogisticated air’. Lavoisier carried out an experiment with a burning candle. As the candle burned, the water gradually rose within the beaker – the candle was using up some of the air. Lavoisier now realized that what actually took place during combustion was very much the opposite of phlogiston theory. When something burned, it didn’t release some mythical phlogiston, but rather combined with the so-called ‘dephlogisticated air’, which made up one fifth of the air.
Lavoisier decided to rename this element ‘oxygen’ – from the Greek oxy – meaning ‘acid’ and-gen ‘generator or producer’. This was a rational name for the new gas: Lavoisier’s experiments had led him to the conclusion that this elemental gas was present in all acids. This appeared to be true at the time. It was only disproved when Davy discovered chlorine was an element, a generation after Scheele had originally discovered this pungent green gas. Davy went on to show that hydrochloric acid contained hydrogen and chlorine, but no oxygen, and the name oxygen was thus shown to be anomalous. But by then it was too late to change it.
With the advent of the Industrial Revolution, science had now emerged as a social phenomenon, and as such was becoming dragged into European nationalistic rivalries.
Combustion was recognized as one of the main chemical processes; its similarity to rusting had already been noticed by Stahl. Lavoisier now conducted a series of experiments which demonstrated that respiration too was a similar process. Lavoisier operated on the principle that the substances taking part in a chemical reaction could be transformed, but their overall weight would always remain the same. It is this idea which is behind the law of conservation of matter. This basic assumption of Lavoisier’s experiments was to become one of the cornerstones of nineteenth-century chemistry. Combustion was oxidation, the addition of oxygen – which in burning formed ash, in rusting formed ‘calx’, in respiration formed ‘fixed air’ (carbon dioxide) and so forth. As can be seen from the above names, chemistry was now stumbling into a morass of contradictory nomenclature.
In the book which Lavoisier co-authored in 1787, Method of Chemical Nomenclature, a logical system of chemical naming was proposed. In future all compounds should be named rationally, after the elements of which they were composed. Chemistry was making progress through measured, scientifically conducted experiments – and these could now be described in scientific language. It is almost impossible to exaggerate the importance of this step.
Lavoisier is admitting that we might never discover precisely what an element is – we are forced to rely upon what appears to be an element, in the light of experimental practice. Chemistry was learning to admit what it did not know – and thus gain a deeper understanding of precisely what it did know. This too was a revolutionary advance in scientific method. Previously the elements had been defined theoretically.
It is surely no coincidence that the greatest philosopher of the age was at this very moment formulating the metaphysical counterpart of such ideas. Almost a thousand miles away on the chilly shores of the Baltic in Konigsberg, Immanuel Kant was outlining a philosophical world which consisted of two components: ‘phenomena’ and ‘noumena’. The former were the appearance of things, as we perceive them through our senses, measurement and so forth. The latter were the unknowable core, the true world beyond the reach of our senses: the truth which supported and gave rise to these phenomena.
The list of the elements which Lavoisier drew up in his Elementary Treatise on Chemistry is surprisingly accurate. In all, he named thirty-three elements. Eight of these, including ‘magnesia’ and ‘lime’, have since been shown to be compounds (magnesium oxide and calcium oxide). Only two were utterly wrong. These were the elements he named as ‘light’ and ‘caloric’ (heat). Once thought to be material substances, these are now known to be forms of energy. Yet such cavils were far outweighed by Lavoisier’s positive contribution. His definition of an element pointed the way forward for future exploration of the elements.
A Formula for Chemistry
Others were quick to build on the foundations of the new chemistry which Lavoisier had laid down. The most striking development came from the Englishman John Dalton.
John Dalton was born in 1766 in the remote village of Eaglesfield. Not until he was past thirty did Dalton seriously turn his attention to chemistry. Accepting Boyle’s notion that gases consist of tiny particles, he soon discovered a fundamental property of gases which to this day is known as Dalton’s Law. This states that when two or more gases are mixed, their combined pressure will be the same as the added pressures of each gas if it was alone, occupying the same volume.
Dalton recognized the similarity of these ultimate, indestructible particles to Democritus’ idea of the ‘uncuttable’ atomos, and decided to call them atoms. But this was not simply a crib of the ancient Greek idea which had been so miraculously preserved and passed on through the works of Epicurus, then Lucretius, and finally through the sole surviving medieval copy of his De Rerum Natura. Nor indeed was it identical with any of the ensuing seventeenth- and eighteenth-century versions of this idea – such as Boyle’s – none of which substantially advanced the Greek notion. All such ideas had remained utterly speculative and theoretical. Dalton’s notion of the atom was scientific and practical.
Dalton’s was a quantitative theory which combined Democritus’ original concept with Lavoisier’s application of quantitative measurement to chemistry. Dalton’s atomic theory stated that all elements consisted of minuscule, indestructible atoms. Following on from Lavoisier, he held that all compound substances were simple combinations of these atoms. This momentous idea transformed our understanding of matter. Having established that, different elemental atoms had weights relative to one another, the next obvious step was to establish a marker. Hydrogen was the lightest element, so Dalton fixed this at a notional relative weight of 1. In this way he built up a table of atomic weights, listing each element with its weight in relation to that of hydrogen.
One further refinement was required before chemistry would be set free from the restraints of its own history. This was to be supplied by the greatest in the long line of Swedish chemists, Jons Berzelius. His first major work was done in electrochemistry, which he played a major role in developing. This new field had been made possible with the invention in 1800 of the electric battery, by the Italian Alessandro Volta, after whom the volt is named. Using the new ‘voltaic pile’ (as the battery was first called), Berzelius ran an electric current through solutions of different compounds. This caused them to separate, with one part attracted to the anode (positive terminal) and one to the cathode (negative). This process came to be known as electrolysis (literally ‘electrical-unbinding’).
It appeared that all compounds were dualistic, consisting of a positive and a negative component, held together by their opposing electrical charge. He had discovered an entirely new way of listing the elements, one which appeared to bear no precise relation to their atomic weights.
Berzelius was a persistent and meticulous experimenter. By 1818 he had determined atomic weights for forty-five of the forty-nine accepted elements. At the same time, he had also analysed over two thousand compounds in the attempt to confirm his dualistic theory.
When science uses explanations or theories which go beyond experimental evidence, it leaves itself open to question. Science is what works, not a philosophical explanation of the world.
During Berzelius’ time chemistry began to rely upon one particular entity, which became an essential component of all experiments, yet was never supported by any experimental evidence whatsoever. And this lasted almost as long as phlogiston and the ‘life-force’. The entity concerned was the atom.
Lavoisier had set out the infrastructure of chemistry. Berzelius added the finishing touches to this project. Chemistry was now well established as an international science – yet unlike mathematics, for example, it had no international language. Lavoisier had indicated the way forward by forming names for new elements, such as oxygen and hydrogen, from ancient Greek descriptions of their distinctive properties. Berzelius used his authority to promulgate this notion throughout the scientific world, insisting that in scientific papers the elements should be called by their ancient Greek or Latin names. But this was only the first step. From earliest times alchemists had represented chemical reactions by formulae, using secret symbols, hieroglyphs and pictographs to depict the starting ingredients and the end products. Lavoisier had understood the usefulness of such formulae, as long as the symbols used were known to all. Dalton understood the need for a much simpler symbolism. Since he visualized atoms as tiny circular entities, he understandably chose to represent the elements in circular form. It was Berzelius who saw the simple answer. He decided that in all chemical equations the element should be represented by the initial letter of its classical Greek or Latin name. Where two elements had the same initial, a second distinguishing letter from the classical name should be added.
Chemistry at last had its own universal language, like mathematics.
The Search for a Hidden Structure
In the wake of Lavoisier, the systematic approach and new experimental techniques soon led to the discovery of a host of new elements. During the life of Berzelius (1779-1848) no fewer than thirty-two new elements were isolated, bringing the total up to fifty-seven. The British scientist Sir Humphry Davy alone discovered six elements.
Several elements were being discovered almost every decade. This profusion of new elements with an ever-widening range of properties soon began to provoke questions. Precisely how many elements were there? Had most of them already been discovered? Or would there perhaps turn out to be innumerable elements?
Johan Dobereiner, the professor of chemistry at the University of Jena. In 1829 he noticed that the recently discovered element bromine had properties which seemed to lie midway between those of chlorine and iodine. Dobereiner began studying the list of the known elements, recorded with their properties and atomic weights, and eventually discovered another two groups of elements with the same pattern. Dobereiner named these groups triads, and began an extensive search of the elements for further examples, but could find no more. Dobereiner’s ‘law of triads’ appeared to apply only to nine of the fifty-four known elements, and was dismissed by his contemporaries as mere coincidence.
It would be over thirty years after Dobereiner’s law of triads before another significant attempt was made to discover a pattern in the elements.
Alexandre-Emile Beguyer de Chancourtois was born in Paris in 1820. De Chancourtois didn’t turn his considerable talents to chemistry until he was in his forties. In 1862 he produced a paper describing his ingenious ‘telluric screw’ , which demonstrated that there did indeed appear to be some kind of pattern amongst the elements.
In 1864 the young English chemist John Newlands came up with his own pattern of the elements, unaware of de Chancourtois’ cryptic researches. John Newlands was born in London in 1837, the son of a Presbyterian minister.
Newlands discovered that if he listed the elements in ascending order of their atomic weights, in vertical lines of seven, the properties of the elements along the corresponding horizontal lines were remarkably similar. He named this his ‘law of octaves’.
Dobereiner had spotted resemblances between isolated groups of elements. De Chancourtois had discerned a certain pattern of recurrent properties. Newlands had extended this pattern and even incorporated Dobereiner’s groups.
It was becoming increasingly obvious that there was some kind of pattern to the elements, but the answer was evidently more complex.
Euclid had laid the foundations of geometry, Newton’s gravity had explained the world in terms of physics and Darwin had accounted for the evolution of all species – could chemistry now discover the secret which accounted for the diversity of matter?
Mendeleyev
Dmitri Ivanovich Mendeleyev was born on 8 February 1834. Or 27 January, according to the old Julian calendar, which was still in use in Russia.
Now that new elements were being discovered every few years, chemistry was beginning to displace physics as the science which caught the public imagination.
After Paris, Mendeleyev set off for Heidelberg. Here he briefly attended lectures by Gustav Kirchhoff. Kirchhoff’s great partner was Robert Bunsen. Between them, Kirchhoff and Bunsen developed the spectroscope, which uses a prism to refract light. As Newton had shown, when light passes through a prism the different wavelengths of which the light consists are refracted in varying degrees, so that it breaks up into a spectrum of its constituent colours.
Continuing with this spectroscopic method, Kirchhoff went on to discover half a dozen new elements in the sun which had not so far been found on earth.
Mendeleyev found himself in the right place at the right time. At Heidelberg his knowledge of the chemical elements benefited greatly from the discoveries going on around him. Working with Bunsen, he had privileged access to the very latest developments.
But Mendeleyev’s ability to detect resemblances between apparently disparate findings now underwent a significant development. He evolved an uncanny ability to detect an underlying principle amidst a welter of seemingly commonplace findings.
The valency of an element is as fundamental as its properties. It too is a defining characteristic of an element. Mendeleyev grasped this vital point early in his seemingly minor study of the solubility of alcohol in water.
In September 1860 the first ever international chemistry congress was called at Karlsruhe in Germany to thrash out this matter. The congress attracted leading chemists from all over Europe, as well as many who had yet to make their name, like Mendeleyev. The future of chemistry depended upon the outcome.
Mendeleyev’s understanding of the nature of the atom and its atomic weight underwent a significant deepening. Without this crucial notion of atomic weight, any prospect of discovering a pattern amongst the properties of the elements would have been out of the question.
By early 1869 Mendeleyev had completed the first volume of his projected two-volume The Principles of Chemistry. This was to be his masterpiece: the finest chemistry textbook of its era.
Despite its likeness to its author, The Principles of Chemistry is no work of woolly eccentricity. This goldmine of information had a very definite structure. The elements, and their compounds, were treated together in groups with similar properties, each following on from the previous ones. For instance, the end of the first volume covered the halogen group, consisting of fluorine, chlorine, bromine and iodine. Each of the halogen group of elements combined with sodium to produce salts which had very similar properties, the best known of these being of course table salt – sodium chloride. The halogens also combined readily with potassium. So, the obvious logical step was to start volume two with the alkali metals group, which contained sodium and potassium. This Mendeleyev reckoned would occupy the first two chapters. Mendeleyev now faced the pressing problem of what group of elements to deal with next.
De Chancourtois claimed to have discovered some kind of recurring pattern. Mendeleyev felt certain that de Chancourtois was right. The entire weight of his chemical knowledge inclined him in favour of this intuition.
Mendeleyev evidently felt certain that the key lay in this natural and obvious clue – the ascending order of weights. Here undeniably was one order. The trouble was, it didn’t appear to explain anything: just that one element was heavier than another.
He began writing out the names of the elements on a series of blank cards, adding their atomic weights and chemical properties. What Mendeleyev had noticed was the similarity between the elements and the game of patience. In patience the cards had to be aligned according to suit and descending numerical order.
What Mendeleyev was looking for amongst the elements appeared to be something very similar: a pattern listing the elements according to groups of similar properties (like the suits), with the elements in each group aligned in sequence of their atomic weights (echoing the sequence of numerical order in the suits).
The Periodic Table
In Mendeleyev’s own words: ‘I saw in a dream a table where all the elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper.’ In his dream, Mendeleyev had realized that when the elements were listed in order of their atomic weights, their properties repeated in a series of periodic intervals. For this reason, he named his discovery the Periodic Table of the Elements.
Mendeleyev’s Periodic Table followed a less rigid pattern, yet this pattern seemed to encompass all the known elements. Where no element fitted into the pattern, he simply left a gap. He predicted that these gaps would one day be filled by elements which had not yet been discovered. Despite these apparent anomalies in his Periodic Table, Mendeleyev felt sure that he was right.
But Mendeleyev’s Periodic Table was soon to receive support in a manner which he least expected. The German scientist Julius Meyer published a paper claiming that he had discovered the Periodic Table. This was surely more than just a misguided coincidence. The lives of Mendeleyev and Meyer in fact contained several coincidences.
Working along similar lines to Mendeleyev, Meyer had eventually discovered an almost identical pattern amongst the elements, at precisely the same time as Mendeleyev. So why is Mendeleyev given credit for the discovery of the Periodic Table? For a start, because he published his paper on the subject on 1 March 1869, just two weeks after his initial discovery – whereas Meyer didn’t publish until the following year.
With the Periodic Table chemistry came of age. Like the axioms of geometry, Newtonian physics and Darwinian biology, chemistry now had a central idea upon which an entire new range of science could be built. Mendeleyev had classified the building blocks of the universe.
Nuclear physics has mostly confirmed Mendeleyev’s original hunches concerning atomic weights, missing elements and their properties.
What Mendeleyev discovered on 17 February 1869 was the culmination of a two-and-a-half-thousand-year epic: a wayward parable of human aspiration.
