Berzelius introduces the concept of isomerism
The notion of substances with the same composition but different properties: one and the same formula, different structure, different reactions.
The notion was formulated in 1830 by the Swedish chemist Jöns Jakob Berzelius, after a series of cases, among them Wöhler's ammonium cyanate and urea. It was this theme, not the vitalist one, that was the main content of the Wöhler-Berzelius correspondence in 1828.
Isomerism became one of the foundations of structural organic chemistry.
Why this date
medium: the year 1830 is generally accepted in the historiography; the extracted sources confirm only that Berzelius introduced the term (Britannica), without a date
Links under review
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Wöhler: artificial formation of urea from ammonium cyanate
influenced · Confidence: high
The link rests on the same paywalled Ramberg 2000 (Ambix 47(3)); we currently cite a personal upload on academia.edu, whose HTML carries only the abstract. No historian asserting this link in open access was found: Esteban (J. Chem. Educ. 85, 1201) and Brooke (BJHS) are paywalled too. The 1828 and 1830 primary sources are available but do not themselves assert the link.
Wöhler's experiment supplied a concrete new example of substances with the same composition and different properties, which entered the foundation of the concept of isomerism.
Link sources
- Ramberg 2000 (2000)
provided a concrete new example of what would later be called isomerism
- Wöhler 1828, Ramberg 2000 (1828)
two entirely different bodies could contain the same proportions of the same elements, and only a dissimilar kind of union brings out the peculiarities
- Ramberg 2000 (2000)
Node sources
- Britannica, Jöns Jacob Berzelius (A man of influence) (2024)
Berzelius also characterized and named two new concepts: “isomerism,” in which chemically diverse substances possess the same composition; and “catalysis,” in which certain chemical reactions are facilitated by the presence of substances that are themselves unaffected.
- Britannica, Jöns Jacob Berzelius (A man of influence) (2024) Verified 20 Sep 2026, quotation assembled from fragments
...his investigation of isomerism and catalysis, phenomena that owe their names to him.
- Ramberg P. J. Ambix 47(3), 170-195 (2000)
In the famous 1828 letter to Berzelius, Wohler explained the rationale for his synthesis. It was to be a minor test for the existence of what would soon be called isomers. “I considered it possible that in the union of cyanic acid with ammonia, the elements could combine in the same proportions, but in another manner... [The formation of urea] would thus be an indisputable example that two entirely different bodies could contain the same proportions of the same elements, and only a dissimilar kind of union brings out the peculiarities in the properties.”
- Ramberg P. J. Ambix 47(3), 170-195 (2000)
While Berzelius clearly seemed excited about the discovery, he did not raise the issues of any implications for vitalism or the relationship between organic and inorganic chemistry. ... What he considered odd or remarkable was the transformation of a salt-like compound into a compound that had none of the properties of a salt.
- Ramberg P. J. Ambix 47(3), 170-195 (2000)
According to Frankland and his contemporaries, the fundamental problems that were unique to chemistry - among others, understanding isomerism, constitution, and reactivity - required a materialist or reductionist theory that did not rely on biological or physiological concepts such as vital force.
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong. "Assembled from fragments" means the words do not stand together on the page: we found each fragment separately and joined them with an ellipsis.