Per Teodor Cleve (10 February 1840 – 18 June 1905) was a Swedish chemist, biologist, mineralogist, oceanographer, and professor. He discovered the chemical elements holmium and thulium and helped isolate helium from the uranium ore cleveite. Cleve was born in Stockholm and became an assistant professor at the Uppsala University in 1860. He died several months after contracting pleurisy in 1904.

In 1874 Swedish chemist Per Theodor Cleve showed that didymium, then considered an element, was actually comprised of two elements, neodymium and praseodymium. In 1879 he discovered two previously unknown elements, which he named holmium (from the Latin for his home town, Stockholm), and thulium (from Thule, an ancient name for Scandinavia). In the same year his research showed that the properties and position in the periodic table of the element scandium matched the hypothetical element “ekaboron” predicted by Dmitri Mendeleev.

The raven — Korpen pharmacy

The raven refers to Korpen (the raven) pharmacy, located in the old town of Stockholm. This pharmacy was founded in 1674 by Jurgen Brandt, a German immigrant to Sweden. Stortorget is a small public square in Gamla Stan, the old town in central StockholmSweden. It is the oldest square in Stockholm, the historical center on which the medieval urban conglomeration gradually came into being.

[1] Today, the square is frequented by tens of thousands of tourists annually, and is occasionally the scene for demonstrations and performances. It is traditionally renowned for its annual Christmas market offering traditional handicrafts and food.

In Paris Cleve visited the research laboratory of chemist Charles Adolphe Wurtz (1817–1884). The laboratory was unique in Europe in its attraction of young chemists, and here Cleve made many friends. Wurtz drew Cleve’s attention to complex metal compounds. At age twenty-one Cleve published his first research paper on a complex chromium compound he had prepared and analyzed. In this paper he demonstrated that the compound was chromium trichloride-ammonia-water (in a 1:4:1 ratio). He later turned to the study of complex platinum compounds, of which he prepared hundreds. In 1872 Cleve, now thirty-two years old, published the results of this study in the Transactions of the Royal Swedish Academy of Sciences.

Baron Jöns Jacob Berzelius 20 August 1779 – 7 August 1848) was a Swedish chemist. Berzelius is considered, along with Robert BoyleJohn Dalton, and Antoine Lavoisier, to be one of the founders of modern chemistry.

Berzelius began his career as a physician but his researches in physical chemistry were of lasting significance in the development of the subject. He is especially noted for his determination of atomic weights; his experiments led to a more complete depiction of the principles of stoichiometry, or the field of chemical combining proportions. In 1803 Berzelius demonstrated the power of an electrochemical cell to decompose chemicals into pairs of electrically opposite constituents.