Martin Heinrich Klaproth (1 December 1743 – 1 January 1817) was a German chemist. He trained and worked for much of his life as an apothecary, moving in later life to the university. His shop became the second-largest apothecary in Berlin, and the most productive artisanal chemical research center in Europe.
Klaproth was a major systematizer of analytical chemistry, and an independent inventor of gravimetric analysis. His attention to detail and refusal to ignore discrepancies in results led to improvements in the use of apparatus. He was a major figure in understanding the composition of minerals and characterizing the elements.
Klaproth discovered uranium (1789)
He was also involved in the discovery or co-discovery of
chromium (1797) and confirmed the previous discoveries of
Klaproth was a member and director of the Berlin Academy of Sciences. He was recognized internationally as a member of the Royal Society in London, the Institut de France, and the Royal Swedish Academy of Sciences.
Klaproth was born in Wernigerode. He was the son of a tailor, and attended the Latin school at Wernigerode for four years.
For much of his life he followed the profession of apothecary. In 1759, when he was 16 years old, he apprenticed at Quedlinburg. In 1764, he became a journeyman. He trained in pharmacies at Quedlinburg (1759–1766); Hanover (1766–1768, with August Hermann Brande); Berlin (1768); and Danzig (1770).
In 1771, Klaproth returned to Berlin to work for Valentin Rose the Elder as manager of his business. Following Rose's death, Klaproth passed the required examinations to become senior manager. Following his marriage in 1780, he was able to buy his own establishment, the Apotheke zum Baren. Between 1782 and 1800, Klaproth published 84 papers based on researches carried out in the Apotheke's laboratory. His shop was the most productive site of artisanal chemistry investigations in Europe at that time.
Beginning in 1782, he was the assessor of pharmacy for the examining board of the Ober-Collegium Medicum. In 1787 Klaproth was appointed lecturer in chemistry to the Prussian Royal Artillery.
In 1788, Klaproth became an unsalaried member of the Berlin Academy of Sciences. In 1800, he became the salaried director of the Berlin Academy of Sciences. He sold the apothecary and moved to the academy, where he convinced the university to build a new laboratory. Upon completion in 1802, Klaproth moved the equipment from his apothecary laboratory into the new building.
When the University of Berlin was founded in 1810 he was selected to be the professor of chemistry.
He died in Berlin on New Year's Day in 1817.
An exact and conscientious worker, Klaproth did much to improve and systematise the processes of analytical chemistry and mineralogy. His appreciation of the value of quantitative methods led him to become one of the earliest adherents of the Lavoisierian doctrines outside France.
Klaproth was the first to discover uranium, identifying it first in torbernite but doing the majority of his research on it with the mineral pitchblende.
On 24 September 1789 he announced his discovery to the Royal Prussian Academy of sciences in Berlin. He also discovered zirconium in 1789, separating it in the form of its "earth" zirconia, oxide ZrO2. Klaproth analyzed a brightly-colored form of the mineral called "hyacinth" from Ceylon. He gave the new element the name zirconium based on its Persian name "zargun", gold-colored.
Klaproth characterised uranium and zirconium as distinct elements, though he was unable to isolate them.
Klaproth independently discovered cerium (1803), a rare earth element, around the same time as Jöns Jacob Berzelius and Wilhelm Hisinger, in the winter of 1803.