Johan Gadolin

Johan Gadolin (5 June 176015 August 1852) was a Finnish chemist, physicist and mineralogist. Gadolin discovered a "new earth" containing the first rare-earth compound yttrium, which was later determined to be a chemical element. He is also considered the founder of Finnish chemistry research, as the second holder of the Chair of Chemistry at the Royal Academy of Turku (or Åbo Kungliga Akademi). Gadolin was ennobled for his achievements and awarded the Order of Saint Vladimir and the Order of Saint Anna.

Early life and education Johan Gadolin was born in Turku (Swedish name Åbo), Finland (then a part of Sweden). Johan was the son of Jakob Gadolin, professor of physics and theology at Turku. Bergman founded an important research school, and many of his students, including Gadolin, Johan Gottlieb Gahn, and Carl Wilhelm Scheele, became close friends.

Career

Gadolin was fluent in Latin, Finnish, Russian, German, English and French in addition to his native Swedish.

Gadolin was elected a member of the Royal Swedish Academy of Sciences in 1790.

Gadolin became the ordinary professor of chemistry at the Royal Academy of Turku in 1797, after the death of Pehr Adrian Gadd. He retained the position until his retirement in 1822.

Studies of heat Gadolin studied the relationship of heat to chemical changes, in particular, the ability of different substances to absorb heat (specific heat) and the absorption of heat during state changes (latent heat). This thermochemical work required extremely precise measurements. Gadolin published important papers on specific heat by 1784, and on the latent heat of steam in 1791.

Yttrium, the first rare-earth element

Gadolin became famous for his description of the first rare-earth element, yttrium. In 1792 Gadolin received a sample of black, heavy mineral found in a quarry in a Swedish village Ytterby near Stockholm by Carl Axel Arrhenius. By careful experiments, Gadolin determined that approximately 38% of the sample was a previously unknown "earth", an oxide which was later named yttria. Yttria, or yttrium oxide, was the first known rare-earth metal compound—at that time, it was not yet regarded as an element in the modern sense. His work was published in 1794.

The mineral that Gadolin examined was named gadolinite in 1800. Well after his death, the discoverers of the element gadolinium and its oxide gadolinia named them after Gadolin.

In an earlier paper in 1788 Gadolin showed that the same element can show several oxidation states, in his case Sn(II) and Sn(IV) 'by combining itself with larger or smaller amounts of the calcinating substance'. He described the disproportionation reaction:

2 Sn(II) Sn(0) + Sn(IV).

Analytical chemistry

Having established the composition of Prussian blue, Gadolin suggested a method for precipitating ferrous iron as ferro ferricyanide, preceding the work of Gay-Lussac by forty years.

One of Gadolin's latest studies was the chemical analysis of the Chinese alloy pak tong in 1810 and 1827. Also known as alpacca or German silver, it was a less expensive silver substitute often containing copper, zinc, nickel, and tin.

Gadolin is also famous for publishing one of the earliest examples of counter-current condensers. In 1791 he improved a condenser design of his father's by using the "counter-current principle". By requiring water coolant to flow uphill, the effectiveness of the condenser was increased. This principle was later used by Justus Liebig, in what is today usually referred to as a Liebig condenser.

Awards

Gadolin was knighted and is registered under number 245 in the Finnish House of Nobility.

Later life Johan Gadolin married first, at age 35, Hedvig Tihleman, with whom he had nine children. After his wife's death he married, at age 59, Ebba Palander.

The Great Fire of Turku of 1827 started in a bakery and damaged or destroyed much of the town of Åbo. Gadolin's laboratory and collection of minerals near the cathedral were destroyed.