Klaproth

Name: Martin Heinrich Klaproth

Nickname/Alias: Martin Henry Klaproth

Achievements: Advanced the technique of systematic chemical analysis, and discovered uranium and other substances

Born: December 1, 1743; Wernigerode, Brnadenburg, Germany

Died: January 1, 1817; Berlin, Germany (Aged 69)

Field & Discipline: Science; Chemistry; Analytic Chemist

Language: German

Father: Johann Julius Klaproth

Mother: Unknown

Siblings: 2 brothers

Spouse: Sophia Christiana Lekman

Children: 1 son; 3 daughters

Education: Local school

Major Work:

“Contributions to the Chemical Knowledge of Mineral Bodies” (1795-1815)

Life & Times:

In 1770 Klaproth  spent some months in Danzig as a pharmaceutical assistant and the following year settled in Berlin as manager of the apothecary shop owned by Valentine Rose, a well-known scientific figure in the city. They conducted experiments together and in 1780 Klaproth qualified as an apothecary.

He began to publish articles in the scientific press on analysis of substances, and in 1782 published his thesis, “On Phosphorus and distilled Waters.” In the same year he was appointed an Examiner at the Supreme College of Medicine and Health, and was given permission to give private lectures on chemistry. He made a good marriage and set up his own apothecary business.

Over the next five years his numerous publications brought him to the attention of the scientific community and he was elected as a member of the Royal Berlin Academy of Sciences. He presented two courses of lectures a year on chemistry, one of which was for the officers of the Royal Artillery Corps. This led to his appointment in as professor at the newly established Tempelhoff Artillery Academy and then as professor at the Royal War School. He also taught chemistry at the Royal Mining Institute.

From the late 1780’s, Klaproth became the leading analytical chemist in Europe. He discovered new substances and named the composition of many substances including compounds of tellurium, strontium, beryllium and chromium.

In 1789 he analyzed a mineral then known as “pechblende” in which he found the oxide of a new metal - he called it [discovered] uranium*. In the same year, he conducted an analysis of zircon and demonstrated that it was a compound of silica and a new earth which he name zirconia.

In 1793 he published a comparative set of experiments on the nature of carbonates of barytes and strontian and was the first on the continent  to publish information on strontian. In 1795 he analyzed the substance known as red schorl to which he gave the name titanium. In 1798 while analyzing the gold ores of Transylvania, he rediscovered a white metal he called tellurium, and in the same year rediscovered  beryllium. In 1803, at around the same time as the Swedish chemist [work related to] Berzelius* discovered cerium, Klaproth  isolated an earth from a Swedish mineral which he called ceria.

Berzelius subjected ceria to an inentse investigation and was convinced they were mixture of several rare elements. On this basis he persuaded a colleague to try to separate distinct substances. Important as his discoveries were, Klaproth’s greatest contribution was in the development of the techniques of  analysis. He made improvements in the apparatus for analysis.

For example, he substituted a mortar of flint rather than the conventional one of agate, and he analyzed the mortar so that he could calculate how much of the mortar substance might have been added to the constituents he was analyzing. He was fussy about the type of crucible he used, whether it was made of glass, iron, earthenware, platinum or silver, and he took into account the effect it would have on the result of his analysis. He prepared his reagents with great care and made sure they were pure.

When he began to analyze mineral bodies, Klaproth found it difficult to dissolve them in acids; this was something he had to do in order to get an accurate analysis. The conventional method was to render the minerals soluble in acid by heating them with caustic potash or an alkaline carbonate but this was not a valid method when the object was to identify the amount of potash.

Klaproth got round this problem by reducing the mineral to an extremely fine powder and putting it in caustic potash ley until the water had disappeared, then raising the temperature and bringing the whole mixture into a state of fusion in a silver crucible. All minerals which had previously remained insoluble after fusion with an alkaline carbonate dissolved in this way.

So all stony  minerals which contain a notable proportion of silica, in general became soluble after being infused in state of ignition with twice their weight of carbonate of soda.

The method of separating iron and manganese from each other was made public by Klaproth. He applied the same precision to the recording of his results. It was common practice at that time to discount slight discrepancies which occurred in analysis. If, for example, a chemist analyzed and weighted the constituents of 100g of a mineral and then found that the weight of the separate constituents did not add up to 100g, they just ignored the fact  and did not record the discrepancy. Klaproth introduced the method of stating his results exactly as found.

His results generally showed a loss, varying from two per cent to half a per cent. So he would repeat his analysis and if the result was the same, then look for what he’d missed that would make up the missing weight. In this way, he  discovered the presence of potash in minerals. (Others, following after, discovered soda as a constitutent through following this routine; arsenic acid, boracic, phosphoric acid were all discovered as a result of being more rigorous in analysis.)

From 1797-1810, Klaproth was an active member of a small scientific society to discuss esoteric aspects of chemistry.

He was one of earliest adherents of [a fan of] Lavoisier’s* anti-phlogiston theory. His collected chemical works were published as “Contributions to the Chemical Knowledge of Mineral Bodies” (1795-1815). He helped to translate works of foreign chemists such as [translated] Berthollet* and he acted as a consultant for articles on chemistry written for encyclopaedias. Together with with Dr FB Wolff, he produced a six-volume Dictionary  of Chemicals.”

When Rose died in 1808, Klaproth took over management of his laboratory. In 1810 he became a member of the medical deputation attached to the Ministry of the Interior and was also made a member of the Perpetual Court Commission for Medicine. When Berlin University was established in 1810, he became the university’s first professor of chemistry.

In 1811 he was given Order of the Red Eagle by king of Prussia. Klaproth died in 1817.

Extra Connections: Admired the work of chemist [a fan of] Smithson*

Assessment: Klaproth made important advances in the systemizing chemical analysis which resulted in big advances for minerology. When he began his career, chemists did not know the true composition of a single mineral in a pure metallic state.

Oneliner:  MH Klaproth,  discoverer of uranium

Bibliography:

• Brock, William H, The Fontana History of Chemistry, Fontana Press, London, 1992.
• Hudson, John, The History of Chemistry, Macmillan Press Ltd., Basingstoke, Hampshire, 1992.
• Thomson, Thomas, The History of Chemistry, Henry Colburn and Richard Bentley, Publishers, London, 1830.