Italian

That Chemistry has contributed, since the most remote ages, to Mankind scientific and technological development is a shared opinion. Yet, if one thinks it over, it has often played a leading role also in his cultural growth and social changes. Sometimes it had preceded or accompanied the key passages in his history, sometimes it followed and completed them. The following examples, showing several of these interactions, may be particularly useful, especially if one considers the general trend to separate and isolate the humanistic culture from the scientific one, enhancing their differences. Moreover they can stimulate young readers of this magazine to get a deeper knowledge of the events that are here shortly described, and to read again their literature, history, philosophy and art textbooks, in order to ask them for new proofs of the close relationships which have always linked the above branches of learning to the scientific ones, and to Chemistry in particular.

Of course here Chemistry is not seen as the rigorous and complete science we know, but, better, as a body of activities, of watching and essaying, which have had the aim to understand the composition of material objects and to study and reproduce the changes they undergo and the heat exchanges that follow them.

The practice, more or less conscious, of manipulating substances to change them, started before man was able to record their procedures and take note of their effects. As a result of attempts, carried out without any arranged scheme, changing randomly the order of the operations, authentic chemical processes were set up, to extract colouring matter from minerals, plants, insects, shellfishes, to obtain fermented drinks or perfumes, rouges, ointments, to tan hides to make leather or to remove grease from wool and to dye fabrics.

The very name of Phoenicians is bound, through the Greek term  = red, to purple, which they obtained, through a complex procedure, set up around 1600 B.C., from the chemical transformation of the glandular mucous of a shellfish. As to produce 1g of this dye about 10.000 shellfish must be treated, one can understand why purple was so precious and why it was deserved to garnish dresses only of high rank people: Roman senators, Roman Emperors and finally Cardinals of Catholic Church.

Fire turned from passive tool for survival to means of technological development: man learnt to reach higher and higher temperatures, which allowed him, not only to produce earthenware and glass, but also, starting from about 4000 B.C., metals from their ores. The first to be produced was copper, thanks to a purely chemical process: mixed with carbon and to gaseous carbon monoxide given off during combustion, blue-green malachite [CuCO3Cu(OH)2] was chemically reduced to shining golden red beads of metallic copper. It was largely used to produce tool and weapons till contamination (first casual, then deliberate) with arsenic or tin of its ores gave rise to an alloy, much more rigid and tough then copper, and then more suitable to produce weapons. The alloy was named bronze, and its importance is proved by the name that has been given to a period of human history, the Bronze Age. The war of Troy was fought between two armies, both provided with bronze weapons: search for tin ores pushed Phoenicians to sail up to Cornwall coasts, and probably Julius Caesar to plan to invade Britannia.

Born from a chemical process, the Bronze Age ended owing to another chemical process, in which metallic iron or, better, steel, was produced by roasting in a kiln, iron ores, mixed with carbon. The Iron Age started when warriors provided with iron weapons defeated those fighting with bronze ones. For instance, around 1100 B.C., Doric tribes flooded the Greek peninsula, driving out its Mycenaean inhabitants, while, in Canaan, Philistines overcome Israelites until King Saul gave them iron weapons too.

By about 600 B.C., western philosophy began and developed in Miletus, a Greek colony in Asia Minor; its first aim was to investigate natural phenomena, to find the intimate composition of material objects and the causes of their transformations. The attempts to solve such typical chemical problems allowed the setup and the development of those logical and rational schemes, which were later used to investigate ethics, politics, and the finality of man and nature.

By about 200 A.D., at Alexandria in Egypt, the centre of the Hellenistic cosmopolitanism, alchemy developed the art of transforming matter; in it merged Egyptian technique, Greek philosophy and eastern mysticism. Apart from the actual possibility of realizing them, alchemists’ attempts to transmute base metals into gold, or to produce elixir of life, allowed them to gather a large body of knowledge, procedures and instruments, which would be transmitted to future chemists. Arabs went on in this tradition, saving and enlarging knowledge, which was transferred intact to Europeans, when they woke up from their medieval dullness. In his several writings, Albert the Great reports a lot of information on alchemy, so that he is considered to be a great alchemist and has then become the patron Saint of chemists.

The most important recipe the Arabs transferred from China to Europe is probably that for preparing gunpowder, a mixture of saltpetre, sulphur and carbon, whose use upset fighting techniques and, thereafter, political and social balance in Europe. Another chemical reaction had been used as a war tool: Greek fire (a mixture of quicklime, naphtha and sulphur, which burn on water) saved Constantinople from the Arabs siege and prevented Europe from being invaded by them.

Mysticism inherited from the East, joined to the secrecy with which deliberately they were covered, made the alchemists to be seen suspiciously by common people, especially because many of them used their chemical knowledge and technical skill to swindle neighbours. This suspect, which turned into open persecution in darkest times, during wars, famine, plague, is witnessed in many literary works. In his Divina Commedia, Dante Alighieri puts into the tenth pit of hell, between forgers, two alchemists, Griffolino d’Arezzo e Capocchio da Siena, while, in one of his Canterbury Tales (1387), Geoffrey Chaucer gives a negative description of an alchemist, considered a swindler involved in obscure activities to damage people. Finally, the playwright Ben Johnson calls Subtle his Alchemist (1610), to witness his bad opinion of these swindlers.

At the beginning of ‘500, a strange man, who called himself Paracelsus, suggested a deep reform of medical practice, contemporary to the religious one held by Luther, asking physicians to accurately study sick persons and diseases rather than to blindly apply traditional practices. His new therapies were based on medicines extracted, by means of chemical procedures, from plants but, above all, from ores.

The success of Paracelsus therapies stimulated physicians to study more carefully chemical substances, especially salts, increasing popularity and knowledge of Chemistry. As soon as an integer manuscript copy of Lucretius’ De Rerum Natura was rediscovered (1417) and printed (1473), its reading re-proposed the question of substances composition and of causes of their transformations; so the debate between supporters of Aristotelians philosophy of principles and elements and those of a particular structure of matter, which were experimenters rather than thinkers. It was soon evident that philosophy was not able, on its own, to solve this problem, and that the key to solve it laid in the new chemical way to watch and evaluate natural phenomena.

Already at the beginning of ‘600, Jean Beguin had clearly made a distinction between Physics, which studies movements of bodies and Chemistry which has the task to separate them in their components and to rejoin them to make new bodies. Nevertheless, Chemistry was not yet successful to assert itself as an independent science, holding an ancillary role, especially because it was not based on mathematics as those on which Keplero, Galilei and Newton had founded Physics and Astronomy. Newton himself, in Query 31 of his Optiks, invited Chemists to apply the same mathematical principles and instruments, with which he had so successfully described the motions of macroscopic bodies on Earth and Universe, to forces which cause chemical reactions. The problem proved not to have an easy solution, because, while the gravitational attraction is universal and involves all bodies, chemical reagents have a stranger behaviour: many of them do not react with one another; others spontaneously do it, in some instances, with great violence. So, to indicate the attraction between two microscopic bodies which caused a reaction, the anthropomorphic term affinity was preferred to attraction: in 1775, Tornbern Bergman, on the basis of experimental observations, made the hypothesis that substances reaction or decomposition was caused by elective affinities which set up between them. Enchanted by this hypothesis, the German poet Johann Wolfgang Goethe used chemical metaphor in his Elective Affinities, to ascribe the end of a marriage to the interference a man and woman. Borrowed form common language, the chemical word went back to its origins to explain these double decomposition of feelings.

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