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History

Christian von Weigel: the inventor of the counter- current “Liebig condenser”.

by Roberto Poeti 11 March 2021

The chemical laboratories of the first half of the 19th century

Of the complex of Justus von Liebig’s chemical laboratories in Giessen, transformed since 1920 into one of the most interesting science museums in the world, one is struck by the size, the wealth of instruments and equipment. The museum preserves the Institute of Chemistry almost intact, where Liebig worked as a teacher and scientist from 1825 to 1852. It is a unique structure, which has survived to the present day. In those rooms and laboratories, generations of chemists from all over Europe and even the United States were trained under the guidance of a great teacher. Liebig later also taught in Munich. An important space has been dedicated to him at the Deutsches Museum in this city. His laboratory is reconstructed in real size. But among the many “objects” that fill the space of his workshops, in both museums there are two that the visitor perceives as the most important. One is the apparatus for the analysis of organic substances, the other is the apparatus for distillation. In both there is a detail that makes them original. In the first it is the Kalium-apparat for the absorption of carbon dioxide, in the other it is the counter-current condenser in distillation.

But if the authorship of the Kali-apparat is Liebig, the condenser, which bears his name, is not his invention. His merit is to have made it a routine tool, precious in laboratory analysis.

But who is responsible for the invention of the counter-current condenser?

11 March 2021 0 comment

History

The history of distillation up to the 18th century

by Roberto Poeti 2 January 2021

A long story

The history of distillation is closely linked to that of alcohol. The mention of distilling devices can be found in the authors of ancient Greece. But these tools were very primitive because they consisted of boilers heated over a high heat on which a layer of sponges was placed which collected the vapors, condensed them and then was pressed to extract the juice. This process, although primitive, has made it possible to obtain a low-alcohol drink. The Romans do not speak, in their works, of distillation devices. They had a fairly accurate knowledge of fermentation phenomena, they made wine, mead and the Germans had taught them to make a kind of beer. What we know for sure is that alcohol and distillation are the fruit of the practice of the Arabs; in fact, the names, alcohol and alembic, originate from this language.

2 January 2021 0 comment

History

Chemical Crystallography before X-ray Diffraction

by Roberto Poeti 13 September 2020

The crystallography in chemistry

When I taught basic chemistry, at the Industrial Technical Institute in Arezzo town (Italy), one of the first lessons of the course was dedicated to illustrating a laboratory experience that students would perform at home. It was the formation of sodium chloride crystals from a salt solution. After about a week each student brought to school his saucer where they had grown small but regular cubic crystals of salt.

13 September 2020 0 comment

History

“On a New Chemistry Theory” of Archibald Couper

by Roberto Poeti 27 March 2020

Introduction to the Essay “On a New Chemistry Theory” of Archibald Couper

Archibald Scott Couper wrote in 1857 a note about his new chemical theory that was presented by Jean Baptiste Dumas at the French Academy and published in Comptes rendus. His presentation was followed by the publication of an essay entitled “Sur Une Nouvelle Theorie Chimique” in Annales de chimie et de physique. The article appeared soon after in the British magazine Philosophical Magazine entitled “On a New Chemical Theory” which contained some important changes from the version French. Almost simultaneously, Friedrich August Kekulé’s article “The Constitution and Metamorphoses of Chemical Compound and the Chemical Nature of Carbon” appeared in Annalen der Chemie und Pharmacie, in which he came to the same conclusions as Couper.

Couper’s Disappearance

In another article on my blog I described the human and scientific events that made A.S.Couper so extraordinary and interesting. I reserved the precedence of Couper over Kekulè because he appears in this scientific story the most unlucky character, but also more brilliant. After writing his revolutionary essay Couper will soon disappear from the scientific life overwhelmed by his problems. We will no longer remember him. Only Kekulè, on the other hand, will take credit for the discoveries made, and even then famous, it will later become one of the greatest chemists of the nineteenth century.

27 March 2020 0 comment

History

The Tragic Story of a Great Chemist: Archibald Scott Couper (1831-1892)

by Roberto Poeti 26 March 2020

Carbon Chemistry

In the history of Organic Chemistry, to the German chemist Friedrich August Kekulé von Stradonitz (1829 – 1896) is reserved for a pre-eminent place. In 1858 he wrote an article listing two fundamental properties of the carbon atom: valence four and the ability of carbon atoms to bind together. In 1865 he published another paper in which he defined the hexagonal structure of the benzene molecule. These discoveries gave an extraordinary boost to the chemistry of the nineteenth century. Today they constitute the axioms of organic chemistry.

But there’s another chemist

But in the same year 1858, a few weeks after the publication of Kekulè and in a completely independent way, another Scottish chemist Archibald Scott Couper (1831-1892) at only twenty-seven years old published an article “On a new chemical theory ” with the same conclusions to which Kekulè had arrived. The life of this chemist is as interesting as it is tragic. He was born in a small village a few miles from Glasgow in 1831. He was the only surviving son of Archibald Couper, a large cotton weaving plant owner that employed more than 600 workers. Of unsteady health, he had a good and scrupulous upbringing at home. In 1851 he began his undergraduate studies at Glascow in Latin and Greek, traveled to Germany, then continued his studies at the University of Edinburgh in philosophy, logic, metaphysics and moral philosophy. So far there are no references in his notes to chemistry studies.

26 March 2020 0 comment

History

What is the strange object in the center of the Logo of the American Chemical Society?

by Roberto Poeti 17 November 2018

,The Logo of American Chemical Society

At the center of the logo of the American Chemical Society, under the Eagle, there is a strange object made from five balls joined together. But what does it represent? And why is it so important to be included in the logo of one of the most prestigious and oldest chemical society? (Its Foundation is of 1876)

The Logo of American Chemical Society

17 November 2018 0 comment

History

The discovery of artemisinin, an antimalarial, of Youyou Tu , a Chinese chemist

by Roberto Poeti 22 June 2018

A compelling story: the discovery of artemisinina , natural principle antimalarial ,of YouYouTu a Chinese chemist , Nobel Laureate in medicine 2015

What happened in China in the years ‘ 60 of the last century

in the years ‘ 60 of the last century China was shaken by a tragic political movement led by Mao Zedong , leader of the country. It was called “cultural revolution” and had protagonist students and lower Communist Party cadres , that were inspired by the contained in “Red Book”, drafted by the same Mao. The victims of the movement were intellectuals and teachers who were subjected to a process of re-education “and suffered abuse of all kinds. Universities and schools stopped their activity for a few years.

22 June 2018 0 comment

History

The D.I.Mendeleev Home Museum in St. Petersburg

by Roberto Poeti 15 November 2017

The Home Museum at the University of St. Petersburg

The article contains a collection of photos and documents translated from Russian, kept preserved in Mendeleev Museum at the University of St. Petersburg. Many thanks to Marina Bekreneva for translation of original documents.

15 November 2017 0 comment

History

Carl Scheele : the discoverer of oxygen

by Roberto Poeti 1 November 2017

Carl Wilhelm Scheele

I rediscovered the great scientist Carl Scheele, a contemporary of Lavoisier, during a trip that I made in Sweden, and in particular in Stockholm. It is first necessary to say a few words about the village of Skansen. Stockholm is a beautiful city built on many islands, one of which, known as Kungliga Djurgarden (Royal Garden), the early nineteenth there were only hills and plants .

The initiative of Artur Hazelius

During the first decade of the nineteenth century a wealthy merchant John Burgman built to Kungliga Djurgarden a belvedere with a magnificent garden. The properties of this Tycoon was called Skansen, as it was near a small fort (skans = small Fortress). The property included more than four acres of land ; in 1891 they passed into the hands of Artur Hazelius. It is due to this extraordinary personage the birth in 1891 the first open-air museum in the world. For nearly twenty years had turned the length and breadth of the Swedish countryside collecting folk costumes, furnishings, furniture and equipment of the old peasant culture and the various trades .

1 November 2017 0 comment

History Teaching Activity

The Stereochemistry in the crystals contained in a wine barrel

by Roberto Poeti 25 July 2017

Red crystal formations : thus was born the stereochemistry

I have kept for many years an old cask in the cellar of my house before deciding to make firewood. Its interior walls, in the dimly lit cellar, seemed covered with blackish storage and amorphous. But when I took her out and was illuminated by sunlight I felt the thrill of discovery. The amorphous layer now appeared made of red crystal formations shaped like shells, which were arranged groups of transparent, colorless prismatic crystals that sparkled like diamonds. It was a unique show.

25 July 2017 0 comment