Martin Heinrich Klaproth
Martin Heinrich Klaproth (born December 1, 1743 in Wernigerode, Harz, Germany and died January 1, 1817 in Berlin) is a Prussian chemist, apothecary and mineralogist.
The young Prussian subject, Martin Henri Klaproth, completed studies in pharmacology and natural philosophy before settling down as an apothecary. After having been successively a pharmacy assistant in Quedlinburg, Hanover, Berlin and Danzig, he came to Berlin on the death of Valentin Rose in 1771 to take over the management of his business. In 1780, he founded a pharmaceutical establishment on his own in the same town and took on responsibilities within the framework of his profession. In 1782, he was already pharmaceutical assessor of the Ober-Collegium Medicum. In 1787, he was appointed lecturer in chemistry and pharmacy in the Royal Prussian Artillery.
He follows with interest the precise demonstrations of the French chemist Antoine de Lavoisier. In 1788, he repeated Lavoisier's experiments at the Berlin Academy of Sciences. The controversies with the partisans of Georg Stahl do not frighten him: he adheres to the point of view of a quantitative chemistry and demands clarity by precise and known operations, and not rantings and pseudo-generalities regarded as categorical. With the partisans of Lavoisienne chemistry, he posed the imperative of the publication of numerical results, chemical analysis can only be founded and improved with this scientific requirement. This humble transparency of research must allow a real control of the data, before showing the still fuzzy demonstrative parts which call for gains in precision and leading to the identification and elimination of the sources of errors, whether they come from the material, errors of reasoning, erroneous handling or simply forgetfulness. The Lavoisienne approach confirms the technical requirement that he had applied to his own approach: he understands that it is necessary to develop simple and practical technical protocols, for example in the case of the technique of drying up to constant mass. The operator on each sample notes the successive weighing results after a controlled and measured drying time. These procedures extend upstream of the experiments, the purification of the reagents is imperative according to reproducible methods known to all.
It is a turning point in his professional life. He abandoned his career as a merchant pharmacist in 1788 to devote himself to chemistry and mineralogy in his laboratory in Berlin. He already teaches chemistry in Berlin. He will become professor of chemistry at the artillery school, as well as at the medico-surgical college, still in Berlin.
He undertook technical studies on mineralogy, in particular by trying out the quantitative chemical analysis of minerals. It shows, in 1788, the identity of composition of calcite and aragonite. These are just two main crystalline varieties of calcium carbonate CaCO3.
In 1789, he described new minerals, uranium and zirconia. He isolated what he believed was a simple semi-metal body called uranite, that is to say in reality an oxide of uranium, from pitchblende extracted from Joachimsthal, then called urane (communication of September 24 1789 at the Royal Prussian Academy of Sciences and entitled “Ueber den Uranit, ein neues Halbmetall”). Uranium metal was not really isolated until 1841 by Eugène-Melchior Péligot.
In 1789, he shows that zirconia or zircon corresponds to an oxide of an unknown element, which he calls zirconium. Berzélius did not prepare the first sample of simple bodies until 1824.
He also analyzes white garnet, red silver or silver and arsenic sulphide, lead molybdate ... He publishes his work in the Mémoires de l