Law of definite proportions of Berzelius. Soon after arriving in Stockholm, Berzelius wrote a chemistry textbook for his medical students,
Lärbok i Kemien, which was his first significant scientific publication. He had conducted experimentation, in preparation for writing this textbook, on the compositions of inorganic compounds, which was his earliest work on definite proportions. introduced his new symbolism, and examined all the known elements. The essay ended with a table of the "specific weights" (relative atomic masses) of the elements, where
oxygen was set to 100, and a selection of compounds written in his new formalism. This work provided evidence in favour of the
atomic theory proposed by
John Dalton: that inorganic chemical compounds are composed of atoms of different elements combined in
whole number amounts. In discovering that atomic weights are not integer multiples of the atomic weight of hydrogen, Berzelius also disproved
Prout's hypothesis that elements are built up from atoms of hydrogen. Berzelius's last revised version of his atomic weight tables was first published in a German translation of his
Textbook of Chemistry in 1826.
Chemical notation In order to aid his experiments, he developed a system of chemical notation in which the elements composing any particular chemical compound were given simple written labels—such as O for oxygen, or Fe for
iron—with their proportions in the chemical compound denoted by numbers. Berzelius thus invented the system of chemical notation still used today, the main difference being that instead of the subscript numbers used today (e.g., H2O or Fe2O3), Berzelius used superscripts (H2O or Fe2O3).
Discovery of elements Berzelius is credited with discovering the
chemical elements
cerium and
selenium and with being the first to isolate
silicon,
thorium,
titanium and
zirconium. Berzelius discovered
cerium in 1803 and
selenium in 1817. Berzelius also discovered how to isolate
silicon in 1824, and
thorium in 1824. Students working in Berzelius's laboratory also discovered
lithium,
lanthanum, and
vanadium. Berzelius discovered amorphous silicon by repeating an experiment performed by Gay-Lussac and Thénard in which they reacted
silicon tetrafluoride with potassium metal which produced very impure silicon. In a variation of this experiment Berzelius heated
potassium fluorosilicate with potassium. It produced potassium silicide which he then stirred with water to produce relatively pure silicon powder. Berzelius recognized this powder as the new element of silicon, which he called silicium, a name proposed earlier by
Davy. Berzelius was the first to isolate
zirconium in 1824, but pure zirconium was not produced until 1925, by
Anton Eduard van Arkel and
Jan Hendrik de Boer.
New chemical terms Berzelius is credited with originating the chemical terms "
catalysis", "
polymer," "
isomer," "
protein" and "
allotrope," although his original definitions in some cases differ significantly from modern usage. At this time the concept of
chemical structure had not yet been developed so that he considered only the numbers of atoms of each element. In this way, he viewed for example
glucose (C6H12O6) as a polymer of
formaldehyde (CH2O), even though we now know that glucose is not a polymer of the
monomer formaldehyde.
Biology and organic chemistry Berzelius was the first person to make the distinction between organic compounds (those containing carbon), and inorganic compounds. In particular, he advised
Gerardus Johannes Mulder in his
elemental analyses of organic compounds such as
coffee,
tea, and various
proteins. The term
protein itself was coined by Berzelius, in 1838, after Mulder observed that all proteins seemed to have the same
empirical formula and came to the erroneous conclusion that they might be composed of a single type of very large
molecule. The term is derived from the Greek, meaning "of the first rank", and Berzelius proposed the name because proteins were so fundamental to living organisms. In 1808, Berzelius discovered that
lactic acid occurs in muscle tissue, not just in milk. The term
biliverdin was coined by Berzelius in 1840, although he preferred "bilifulvin" (yellow/red) over "bilirubin" (red). He likewise coined the name haemato-globulin which is the
etymological origin for
hemoglobin.
Vitalism Berzelius stated in 1810 that living things work by some mysterious "vital force", a hypothesis called
vitalism. Vitalism had first been proposed by prior researchers, although Berzelius contended that compounds could be distinguished by whether they required any organisms in their
synthesis (
organic compounds) or whether they did not (
inorganic compounds). However, in 1828,
Friedrich Wöhler accidentally obtained
urea, an organic compound, by heating
ammonium cyanate. This showed that an organic compound such as urea could be prepared synthetically and not exclusively by living organisms. Berzelius corresponded with Wöhler on the urea synthesis findings. However, the notion of vitalism continued to persist, until further work on abiotic synthesis of organic compounds provided substantial evidence against vitalism. == Works ==