Berzelius, Jöns Jakob (1779–1848)

Swedish chemist. He accurately determined more than 2,000 relative atomic and molecular masses. In 1813–14, he devised the system of chemical symbols and formulae now in use and proposed oxygen as a reference standard for atomic masses. His discoveries include the elements cerium in 1804, selenium in 1817, and thorium in 1828; he was the first to prepare silicon in its amorphous form and to isolate zirconium. The words ‘isomerism’, ‘allotropy’, and ‘protein’ were coined by him.

Berzelius noted that some reactions appeared to work faster in the presence of another substance which itself did not appear to change, and postulated that such a substance contained a catalytic force. Platinum, for example, was capable of speeding up reactions between gases. Although he appreciated the nature of catalysis, he was unable to give any real explanation of the mechanism.

Berzelius, born in Östergötland, studied natural sciences and medicine at Uppsala University and began to experiment in chemistry. In 1807 he was appointed professor of medicine and pharmacy at the College of Medicine, Stockholm. Papers he published 1810–16 describe the preparation, purification, and analysis of about 2,000 chemical compounds. In the course of this work he improved many existing methods and developed new techniques. Quantitative analysis on this scale established beyond doubt British chemist John Dalton's atomic theory and French chemist J L Proust's law of definite proportions. It also laid the foundation of Berzelius's determination of the atomic weights of the 40 elements known at that time.

In the early 19th century it became apparent that elements could be grouped by similar chemical properties. Chlorine, bromine, and iodine formed such a grouping. Each of these elements could be found as salts in sea water, so Berzelius coined the name ‘halogens’ (salt formers) to describe the family collectively.

His Textbook of Chemistry 1803 was soon accepted as the definitive work for the time.