Martin Heinrich Klaproth

Martin Heinrich Klaproth (1 December 1743 – 1 January 1817) was a German chemist. For most of his career he worked as an apothecary, only later moving into academia. His own pharmacy grew into the second-largest in Berlin and became the most productive site of artisanal chemical research in Europe.

Klaproth is remembered as a key figure in systematizing analytical chemistry and as an independent developer of gravimetric analysis. His meticulous habits and insistence on investigating inconsistencies led to better laboratory equipment and techniques. He made major contributions to understanding mineral composition and identifying new elements.

Among the elements he discovered were uranium (1789) and zirconium (1789). He also helped discover or co-discover titanium (1795), strontium (1793), cerium (1803), and chromium (1797). Additionally, he confirmed earlier discoveries of tellurium (1798) and beryllium (1798). Klaproth served as a member and later director of the Berlin Academy of Sciences. He was internationally recognized 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, the son of a tailor. He attended the local Latin school for four years. At age sixteen, in 1759, he began an apprenticeship at Quedlinburg. He became a journeyman in 1764. His training took him to pharmacies in Quedlinburg (1759–1766), Hanover (1766–1768, under August Hermann Brande), Berlin (1768), and Danzig (1770).

In 1771 he returned to Berlin to manage the business of Valentin Rose the Elder. After Rose’s death, Klaproth passed the exams to become senior manager. He married in 1780 and bought his own establishment, the Apotheke zum Baren. From 1782 to 1800 he published 84 papers based on work done in that pharmacy’s laboratory. Starting in 1782, he served as assessor of pharmacy for the Ober-Collegium Medicum’s examining board. In 1787 he became a lecturer in chemistry to the Prussian Royal Artillery. He joined the Berlin Academy of Sciences as an unsalaried member in 1788, and in 1800 became its salaried director. He then sold his pharmacy and persuaded the university to build a new laboratory, which opened in 1802. He moved his equipment there. When the University of Berlin was founded in 1810, he was chosen as its professor of chemistry. He died in Berlin on New Year’s Day, 1817.

A precise and diligent worker, Klaproth greatly improved and systematized analytical chemistry and mineralogy. His commitment to quantitative methods made him an early supporter of Lavoisier’s theories outside France. He first identified uranium in torbernite but did most of his research on it using pitchblende, announcing the discovery to the Royal Prussian Academy on 24 September 1789. That same year he discovered zirconium, isolating it as its oxide, zirconia, from a bright-colored Ceylonese mineral called hyacinth; he named the element after its Persian name “zargun,” meaning gold-colored. Although he characterized uranium and zirconium as distinct elements, he could not isolate them. In the winter of 1803, around the same time as Jöns Jacob Berzelius and Wilhelm Hisinger, he independently discovered the rare earth element cerium. Titanium had first been identified by William Gregor in 1791, but his discovery went unnoticed. In 1795 Klaproth verified an unknown oxide in Hungarian rutile and proposed the name “titanium.” Later it was shown that Gregor’s menachanite and Klaproth’s titanium were the same element, and Klaproth’s name was adopted. He also clarified the composition of many poorly understood substances, including compounds of tellurium, strontium, and chromium. Chromium was discovered by Louis Nicolas Vauquelin in 1797 and independently by Klaproth and Tobias Lowitz in 1798 from a Ural Mountains mineral; Klaproth confirmed it as a distinct element. The existence of tellurium had been suggested by Franz-Joseph Mueller von Reichenstein in 1783, and independently by Pál Kitaibel in 1789. Mueller sent a sample to Klaproth in 1796, who isolated the substance and confirmed it as a new element in 1798. Klaproth credited Mueller as the discoverer and suggested the name “tellus,” Latin for earth. In 1790 Adair Crawford and William Cruickshank showed that the mineral strontianite from Scotland was different from barium minerals. Klaproth, along with Thomas Charles Hope and Richard Kirwan, independently studied strontianite, prepared strontium compounds, and distinguished them from barium compounds. Klaproth published his findings on separating strontium from barium in September 1793.