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Georg Brandt's discovery of cobalt

cobalt

Before the 1730s there were only seven metals known to exist and these had been used since antiquity - gold, silver, iron, copper, lead, tin and mercury. In addition, the oxides and sulfides of bismuth, zinc, antimony and arsenic were also in use. A few ancient civilizations some 2000 years in the past, such as the Egyptians, had used a mineral to colour pottery deep blue. They were unaware that the deep blue colour was caused by the presence of the element we now know as cobalt.

In the early 1700s German silver miners and smelters quite understandably mistook cobalt containing ores for copper ores. However, whereas it was a relatively easy process to extract silver from copper ores, they found that there were certain "copper" ores that would not give up their silver by the usually processes. They called these ores kobald, meaning "goblin" or "mischief maker". During the processes of attempting to extract silver, these kobald ores produced poisonous fumes and a residue (regulus) that was able to colour glass deep blue.

For a long time it was thought that the blue colour was due to the presence of bismuth. Brandt was able to separate cobalt from bismuth and prove conclusively that cobalt was responsible for the blue colouration. Between 1735 and 1739 Brandt worked on establishing six relatively simple chemical tests that would distinguish cobalt from bismuth when they were present in the same ores. He succeeded in isolating an impure sample of cobalt in 1742 and went on to discover that it had magnetic properties and could form alloys with iron, tin, copper, gold and antimony.

Brandt was the first to use the term 'semi-metal' to refer to impure metals found in the regulas after smelting (so metals that were still in combination with other elements but showed some metallic properties).

 

 

HISTORY OF SCIENCE AND TECHNOLOGY

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Georg Brandt 1694 - 1768

Georg Brandt was born into a well-off family living in the township of Riddarhyttan in Sweden. His father, Jürgen Brandt, was a retired pharmacist who, aged forty six, married his third wife, Catharina Ysing, who was twenty seven years his junior. There were three children in the family. Catharina, Georg's mother, was the daughter of a wealthy timber mill proprietor.

Jürgen Brandt had a keen interest in mineralogy. He bought a copper smelting works close to Riddarhyttan in 1690. Jurgen passed his enthusiasm for mineralogy onto his son from an early age. Even before he entered university, Georg was a gifted pharmacist and mineralogist.

Georg Brandt attended the University of Uppsala and, in 1714, he became a government employee at the Bureau of Mines. In 1718, aged twenty four, Brandt published the lectures of his mathematics teacher, Andres Gabriel Duhre. He used this as an opportunity to write a preface, influenced by Isaac Newton's work in physics, advocating the need for chemistry to be studied on a more mathematical basis. Brandt was launching his attack on alchemy that he considered was under the control of con-men who were only out to make money.

In 1721 Brandt was awarded a grant from the Bureau of Mines to travel around Europe and research different mining techniques. However , he had other plans. He used the grant, along with the allowance from his father, to pay for his further education. Brandt enrolled at the University of Leiden in the Netherlands. Here his chemistry teacher was Herman Boerhaave who was an anti-alchemist and he encouraged his students to adopt a rigorous practical approach to their studies.

After three years in Leiden, Brandt moved on to study at the University of Rheims in France. He gained an MD in 1726. On his way back to Sweden, presumably to appease the Bureau of Mines, Brandt made a stop in the Hare Mountains to studying the mining and smelting techniques. Brandt's misuse of his grant seems to have been overlooked since he was made Director of the chemistry laboratory at the Bureau in 1729. His work on minerals containing arsenic compounds was published in 1733.

Brandt's career was setting off. In 1730 he was appointed Warden of the Royal Mint and he began teaching chemistry at the Bureau of Mines. One of his students at this time was Fredrik Cronstedt who went on to discover Nickel in 1751. Brandt researched compounds of antimony, bismuth, mercury and zinc found in minerals. He also developed new methods for producing hydrochloric, nitric and sulphuric acids. His research was published in 1741 and 1743.

Brandt is described as being a man of few words who preferred his own company. He was appreciated for his straight forward approach and his word was trusted. Even King Frederick of Sweden is reported to have referred to Brandt as "that honest man". Brandt married Anna Maria Norn in 1734 when he was forty and she was twenty years of age. The couple had one daughter, Catherina Elisabet, who was born in 1735.

Brandt is best know for his identification of cobalt (see details left). He wrote about his discovery in Dissertatis de Semi Metallis in 1735 but it was not published until 1739. His discovery was not immediately accepted as no new metal had been identified since antiquity. Many of Brandt's contemporaries were sceptical about his findings and it was a few years before Brandt's identification of cobalt was added to the record books.

publication

(Translation: On the Colour of Cobalt by Georg Brandt
for the Swedish Royal Academy of Sciences July 30, 1760

 

In 1747 Brandt was made an Associate Member of the Bureau des Mines and he became a full member in 1750. Brandt was one of the first researchers to publicly denounce alchemy. In 1748 he demonstrated to the Royal Swedish Academy of Sciences how alchemists could trick their audiences into believing that they had made gold from another metal. Brandt died from the effects of prostate cancer 1768. He was described by an early biographer as being one of the "ablest chemists of his time".

 

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