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Showing posts with label cobalt. Show all posts
Showing posts with label cobalt. Show all posts

Monday, 13 June 2016

Dagger in Tutankhamun's tomb was made with iron from a meteorite

A dagger entombed with King Tutankhamun was made with iron from a meteorite, a new analysis on the metal composition shows.

In 1925, archaeologist Howard Carter found two daggers, one iron and one with a blade of gold, within the wrapping of the teenage king, who was mummified more than 3,300 years ago. The iron blade, which had a gold handle, rock crystal pommel and lily and jackal-decorated sheath, has puzzled researchers in the decades since Carter’s discovery: ironwork was rare in ancient Egypt, and the dagger’s metal had not rusted.

Italian and Egyptian researchers analysed the metal with an x-ray fluorescence spectrometer to determine its chemical composition, and found its high nickel content, along with its levels of cobalt, “strongly suggests an extraterrestrial origin”. They compared the composition with known meteorites within 2,000km around the Red Sea coast of Egypt, and found similar levels in one meteorite.

That meteorite, named Kharga, was found 150 miles (240km) west of Alexandria, at the seaport city of Mersa Matruh, which in the age of Alexander the Great – the fourth century BC – was known as Amunia.

The researchers published their findings on Tuesday in the journal Meteoritics & Planetary Science.

Although people have worked with copper, bronze and gold since 4,000BC, ironwork came much later, and was rare in ancient Egypt. In 2013, nine blackened iron beads, excavated from a cemetery near the Nile in northern Egypt, were found to have been beaten out of meteorite fragments, and also a nickel-iron alloy. The beads are far older than the young pharaoh, dating to 3,200BC.

“As the only two valuable iron artifacts from ancient Egypt so far accurately analysed are of meteoritic origin,” the team that studied the knife wrote, “we suggest that ancient Egyptians attributed great value to meteoritic iron for the production of fine ornamental or ceremonial objects”.

The researchers also stood with a hypothesis that ancient Egyptians placed great importance on rocks falling from the sky. They suggested that the finding of a meteorite-made dagger adds meaning to the use of the term “iron” in ancient texts, and noted around the 13th century BC, a term “literally translated as ‘iron of the sky’ came into use … to describe all types of iron”.

“Finally, somebody has managed to confirm what we always reasonably assumed,” Thilo Rehren, an archaeologist with University College London, told the Guardian.

Rehren, who studied the nine meteoritic beads, said “there never has been a reason to doubt this outcome but we were never really able to put this hard data behind it”.

He added that other objects from Tutankhamun’s tomb, including jewelry and miniature daggers, are believed to made from meteorite iron.

“Yes, the Egyptians referred to this stuff as metal from the heaven, which is purely descriptive,” he said. “What I find impressive is that they were capable of creating such delicate and well manufactured objects in a metal of which they didn’t have much experience.”

An iron meteorite, by James St. John (Flickr: Murnpeowie Meteorite) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons
The researchers wrote in the new study: “The introduction of the new composite term suggests that the ancient Egyptians were aware that these rare chunks of iron fell from the sky already in the 13th [century] BCE, anticipating Western culture by more than two millennia.”

Egyptologist Joyce Tyldesley, of the University of Manchester, has similarly argued that ancient Egyptians would have revered celestial objects that had plunged to earth.

“The sky was very important to the ancient Egyptians,” she told Nature, apropos of her work on the meteoritic beads. “Something that falls from the sky is going to be considered as a gift from the gods.”

The high quality of the blade suggests that Tutankhamun, who lived during the latest stage of the Bronze Age, was supported by ironworkers who were skilled despite the relative rarity of the material.

The blade may not be the only item derived from falling rocks on Tut’s person.

In 2006, an Austrian astrochemist proposed that an unusual yellowish gem, shaped as a scarab in King Tut’s burial necklace, is actually glass formed in the heat of a meteorite crashing into sand.

“It would be very interesting to analyse more pre-Iron Age artifacts, such as other iron objects found in King Tut’s tomb,” Daniela Comelli, of the physics department at Milan Polytechnic, told Discovery News. “We could gain precious insights into metal working technologies in ancient Egypt and the Mediterranean.”

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Tuesday, 8 March 2016

Celebrating women in science on International Women’s Day: Dorothy Mary Hodgkin

Dorothy Mary Hodgkin OM FRS (12 May 1910 – 29 July 1994), known professionally as Dorothy Crowfoot Hodgkin or simply Dorothy Hodgkin, was a British biochemist who developed protein crystallography, for which she won the Nobel Prize in Chemistry in 1964.

She advanced the technique of X-ray crystallography, a method used to determine the three-dimensional structures of biomolecules. Among her most influential discoveries are the confirmation of the structure of penicillin that Ernst Boris Chain and Edward Abraham had previously surmised, demonstrating (contrary to scientific opinion at the time) that it contains a β-lactam ring. She also confirmed the structure of vitamin B12, for which she became the third woman to win the Nobel Prize in Chemistry.  In 1945, working with C. H. (Harry) Carlisle, she published the first such structure of a steroid, cholesteryl iodide (having worked with cholesteryls since the days of her doctoral studies). 

In 1948, Hodgkin first encountered vitamin B12 and created new crystals. Vitamin B12 had first been discovered by Merck earlier that year. Vitamin B12 had a structure at the time that was almost completely unknown, and when Hodgkin discovered it contained cobalt, she realized the structure actualization may be determined by x-ray crystallography analysis. The large size of the molecule, and that the atoms were largely unaccounted for - aside from cobalt - posed a challenge in structure analysis that hadn't been previously explored.

Molecular structure of vitamin B12, by NEUROtiker (Own work) [Public domain], via Wikimedia Commons

From these crystals, she deduced the presence of a ring structure because the crystals were pleochroic, a finding which she later confirmed using X-ray crystallography. The B12 study published by Hodgkin was described by Lawrence Bragg as being as significant "as breaking the sound barrier." Scientists from Merck had previously crystallised B12, but had published only refractive indices of the substance. The final structure of B12, for which Hodgkin was later awarded the Nobel Prize, was published in 1955.

In 1969, after 35 years of work and five years after winning the Nobel Prize, Hodgkin was able to decipher the structure of insulin. X-ray crystallography became a widely used tool and was critical in later determining the structures of many biological molecules where knowledge of structure is critical to an understanding of function. She is regarded as one of the pioneer scientists in the field of X-ray crystallography studies of biomolecules.

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Friday, 24 January 2014

Cobalt!

Cobalt is a chemical element with symbol Co and atomic number 27. Like nickel, cobalt in the Earth's crust is found only in chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, produced by reductive smelting, is a hard, lustrous, silver-grey metal.


Cobalt-based blue pigments (cobalt blue) have been used since ancient times for jewellery and paints, and to tint glass blue, but the colour was later thought by alchemists to be due to the known metal bismuth. Miners had long used the name kobold ore (German for goblin ore) for some of the blue-pigment producing minerals; they were named because they were poor in known metals, and gave poisonous arsenic-containing fumes upon smelting. In 1735, such ores were found to be reducible to a new metal (the first discovered since ancient times), and this was ultimately named for the kobold.

Cobalt is primarily used as the metal, in the preparation of magnetic, wear-resistant and high-strength alloys. Its compounds cobalt silicate and cobalt(II) aluminate (CoAl2O4, cobalt blue) give a distinctive deep blue color to glass, ceramics, inks, paints and varnishes.

Cobalt blue tinted glass

Free cobalt (the native metal) is not found in on Earth, except as recently delivered in meteoric iron (see below). Though the element is of medium abundance, natural compounds of cobalt are numerous. Small amounts of cobalt compounds are found in most rocks, soil, plants, and animals.

Cobalt forms many useful alloys. It is alloyed with iron, nickel, and other metals to form Alnico, an alloy with exceptional magnetic strength. Cobalt, chromium, and tungsten may be alloyed to form Stellite, which is used for high-temperature, high-speed cutting tools and dies. Cobalt is used in magnet steels and stainless steels. It is used in electroplating because of its hardness and resistance to oxidation. Cobalt salts are used to impart permanent brilliant blue colours to glass, pottery, enamels, tiles, and porcelain. Cobalt is used to make Sevre's and Thenard's blue. A cobalt chloride solution is used to make a sympathetic ink. Cobalt is essential for nutrition in many animals. Cobalt-60 is an important gamma source, tracer, and radiotherapeutic agent.



For more information visit:-
http://en.wikipedia.org/wiki/Cobalt
http://www.theguardian.com/science/punctuated-equilibrium/2011/sep/02/1?guni=Article:in%20body%20link