Cobalt was
discovered in 1735 by a Swedish chemist named Georg Brandt in Stockholm, Sweden.
Brandt was attempting to prove that the ability of certain minerals to color
glass blue was due to an unknown element and not to bismuth, as was commonly
believed at the time. Cobalt’s primary ores are cobaltite (CoAsS) and erythrite
(Co3(AsO4)2). Cobalt is usually recovered as a by-product of mining and
refining nickel, silver, lead, copper and iron. Cobalt gets its name from the German word
“kobalt” which means “goblin.”  Miners gave cobalt ore this name as they
where superstitious about mining the ore. It all started in 1730, when chemist
Georg Brandt of Stockholm became interested in a dark blue ore from some local
copper workings, and he eventually proved that it contained a hitherto
unrecognised metal and he gave it the name by which its ore was cursed by
miners in Germany, where it was sometimes mistaken for a silver ore. He
published his results in 1739. For many years his claim to have uncovered a new
metal was disputed by other chemists who said his new element was really a
compound of iron and arsenic, but eventually it was recognised as an element in
its own right. Cobalt is a brittle, hard, silver-grey transition metal
with magnetic properties similar to those of iron (it is ferromagnetic). It has
a high melting point and is hard-wearing even at high temperatures. Its alloys
also possess useful properties and so it finds use in high speed steels and
cutting tools for instance. Cobalt is also used to make alloys for jet engines
and gas turbines, magnetic steels and some types of stainless steels. It has a 1,495
°C melting point and a 2,870 °C boiling point. The element is active
chemically, forming many compounds. Cobalt is stable in air and unaffected by
water, but is slowly attacked by dilute acids. Also, the radioactive isotopes,
cobalt-60, is used in medical treatment and also to irradiate food, in order to
preserve the food and protect the consumer. Cobalt is found in the minerals
cobaltite, skutterudite and erythrite. Important ore deposits are found in DR
Congo, Canada, Australia, Zambia and Brazil. Most cobalt is formed as a
by-product of nickel refining. Like nickel, cobalt is found in the Earth’s
crust 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-gray metal. It is also found in rocks, sea and mineral
waters, coal, meteorites, the sun and stellar atmospheres, soils, plants and
animals. Cobalt is used to make alloys for jet engines and gas turbines,
magnetic steels and some types of stainless steels. Cobalt-60, a radioactive
isotope of cobalt, is an important source of gamma rays and is used to treat
some forms of cancer and as a medical tracer. As in ancient times, cobalt is
still used in pigments today. About 30 percent of cobalt produced annually goes
to the ceramic and paint industries, according to Nature Chemistry. In nickel
smelting, most of the cobalt is recovered during electrolytic refining of the
nickel by precipitation from solution, usually as a cobaltic hydroxide. … In
refineries using a chloride leach for nickel matte, solvent extraction is used
to remove cobalt directly from the pregnant solution, purifying it.




Frederick Soddy

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Frederick Soddy (2 September 1877 – 22 September 1956) was born at 5
Bolton Road, Eastbourne, England. He went to school at Eastbourne College, before
going on to study at University College of Wales at Aberystwyth and at Merton
College, Oxford, where he graduated in 1898 with first class honors in
chemistry. He was a researcher at Oxford from 1898 to 1900. He was also an
English radiochemist who explained, with Ernest Rutherford, that radioactivity
is due to the transmutation of elements, now known to involve nuclear
reactions. He also proved the existence of isotopes of certain radioactive
elements. The existence
of isotopes was first suggested in 1913 by Frederick Soddy, based on studies of
radioactive decay chains that indicated about 40 different species referred to
as radioelements (i.e. radioactive elements) between uranium and lead, although
the periodic table only allowed for 11 elements from uranium to lead. Several
attempts to separate these new radioelements chemically had failed before
Soddy. For example, Soddy had shown in 1910 that mesothorium (later shown to be
228Ra), radium (226Ra, the longest-lived isotope), and thorium X (224Ra) are
impossible to separate. Attempts to place the radioelements in the periodic
table led Soddy and Kazimierz Fajans independently to propose their radioactive
displacement law in 1913, to the effect that alpha decay produced an element
two places to the left in the periodic table, whereas beta decay emission
produced an element one place to the right. Soddy recognized that emission of
an alpha particle followed by two beta particles led to the formation of an
element chemically identical to the initial element but with a mass four units
lighter and with different radioactive properties. Soddy proposed that several
types of atoms (differing in radioactive properties) could occupy the same
place in the table. For example, the alpha-decay of uranium-235 forms
thorium-231, whereas the beta decay of actinium-230 forms thorium-230. The term
“isotope”, Greek for “at the same place”, was suggested to Soddy
by Margaret Todd, a Scottish physician and family friend, during a conversation
in which he explained his ideas to her. After this discovery, Frederick received
a Nobel prize one year later. Soddy also did work with other scientists, such
as in 1903, with Sir William Ramsay at University College London, Soddy showed
that the decay of radium produced helium gas. In the experiment a sample of
radium was enclosed in a thin-walled glass envelope sited within an evacuated
glass bulb. After leaving the experiment running for a long period of time, a
spectral analysis of the contents of the former evacuated space revealed the
presence of helium. Later in 1907, Rutherford and Thomas Royds showed that the
helium was first formed as positively charged nuclei of helium (He2+) which
were identical to alpha particles, which could pass through the thin glass wall
but were contained within the surrounding glass envelope. Soddy also rediscovered
the Descartes’ theorem in 1936 and published it as a poem, “The Kiss
Precise”, quoted at Problem of Apollonius. The kissing circles in this
problem are sometimes known as Soddy circles.

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