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History

The story of the “Green Scheele” pigment by swedish chemist Carl Scheele

by Roberto Poeti 29 May 2022

Carl Scheele’s pigments

The intense experimental activity of Carl Scheele (1742-1786) embraced the fields of organic and inorganic chemistry, obtaining incredible results in his short life (he died at the age of forty), having the back rooms of the pharmacies where he worked. There are Scheele’s discoveries that have had a great impact, such as the discovery of oxygen on the development of chemistry, his research on phosphorus in the Swedish match industry, or his investigations on the photochemistry of silver salts on the development of photography etc. But there is an experimental result by Scheele, not among the most important in terms of scientific relevance, which however had the most impact on art, fashion and costume in general. It is the invention of the green dye which then took the name green of Scheele, the link between the pigments and Scheele was the unexpected result of research that had a different purpose.

29 May 2022 0 commento

History

How did Mendeleev’s first “Periodic Table” come about?

by Roberto Poeti 28 July 2021

The museum

I think there cannot be such a strong emotion for a chemist as that one feels when visiting Mendeleev’s apartment at the University of St. Petersburg. He lived there from 1867 to 1890. The apartment is located on the ground floor of the Faculty of Chemistry and was connected to his laboratory. Since 1911, four years after his death, it has been transformed into a museum. I visited the Museum in 2009 on a trip to St. Petersburg. The paradoxical thing is that I had no idea of the existence of this heritage. On the penultimate day of my stay in St. Petersburg, I realized, consulting the guide for the umpteenth time, that in a corner, in minute letters, the news of the existence of the museum was reported. So in the middle of August, a weekday in Russia, I was able to find the museum with difficulty and visit it. A visit all alone, with Dr. Natalia who was my guide without speaking English, but reading the information written in English from a notebook of her notes. I felt like I was visiting a small country museum without ostentation, all very informal. When you enter the apartment, after walking through a few rooms, you arrive at the study. Here time has stopped, everything has remained as it was when Mendeleev died. On one side of the study there is his desk, his armchair, the chess pieces. And it is precisely here where Mendeleev’s first “Periodic Table” come about

28 July 2021 0 commento

History

William Prout (1785 – 1850): a great chemist and physician

by Roberto Poeti 31 May 2021

William Prout (1785–1850): a multifaceted chemist and physician

Prout’s personal and professional history makes us known as a scholar who has made important contributions in many fields of knowledge, from chemistry to physiology and medicine. In this article we will deal with two aspects of his research both derived from his early work on the relationship between density and atomic weights of gases that he was among the first to set up. The first is the conception of the structure of the atom, the second is the idea of the diatomicity of the molecules of elementary gases.

31 May 2021 2 commenti

History

Where Antoine Lavoisier’s body is buried?

by Roberto Poeti 24 May 2021

The “Sepulcher” of Antoine Lavoisier

The article tells the random discovery made during a short stay in Paris, in search of the places of the history of chemistry. The visit to the catacombs of Paris, one of the many tourist destinations, made us known, through an exhibition set up there, where are the mortal remains of the father of chemistry.

24 May 2021 0 commento

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 commento

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 commento

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 commento

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 commento

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 commento

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 commento