Discovery of Chromium
Chromium was discovered in 1780 by French chemist Nicolas Louis Vauquelin in Paris. He discovered the element in a mineral sample of ‘Siberian red lead’- now known as crocoite (lead chromate).
He boiled the crushed mineral with potassium carbonate to produce lead carbonate and a yellow potassium salt solution of chromic acid.
Vauquelin was convinced by further experiments on the solution that he had found a new metal.
In 1781 he succeeded in isolating the metal. Initially he removed the lead from the mineral sample by precipitation with hydrochloric acid. Vauquelin then obtained the oxide by evaporation and finally isolated chromium by heating the oxide in a charcoal oven.
Vauquelin also identified small amounts of chromium in ruby and emerald stones.
Vauquelin went on to discover Beryllium in 1798.
Chromium was named from the Greek word ‘chroma’, meaning color because it forms a variety of colorful compounds.
Hamedan is one of the oldest cities of not only Iran but of the world. It’s historical origins date back to several centuries Before Christ. Today’s Hamedan is what is left of Ecbatana,The Mede’s capital before they formed a union with Persians.The poet Ferdowsi says that Ecbatana was build by king Jamshid, , a king who was maybe somewhat hastily described as legendary.According to historical records ,there was once a castle in this city by the name of Haft Hessar (Seven Walls) which had a thousands rooms and its grandeur equalled that of the Babylon Tower.Hamedan , which was the summer capital of the Median and Achaemenid was then called Ekbatan or Hegmataneh;meaning a place of assembly. A more interesting sight for tourists who may not have seen any before are the Cuniform inscriptions engraved on a cliff at the bottom of a green valley,called Ganj Nameh.Hamedan as a city in the western region of Iran played a key role in the Silk Roadand had a great prosperity in commerce and trade being on the main road
Discovery of Titanium
Titanium’s discovery was announced in 1791 by the amateur geologist Reverend William Gregor from Cornwall, England.
Gregor found a black, magnetic sand that looked like gunpowder in a stream in the parish of Mannacan in Cornwall, England. (We now call this sand ilmenite; it is a mixture consisting mainly of the oxides of iron and titanium.)
Gregor analyzed the sand, finding it was largely magnetite (Fe3O4) and the rather impure oxide of a new metal, which he described as ‘reddish brown calx.’
This calx turned yellow when dissolved in sulfuric acid and purple when reduced with iron, tin or zinc. Gregor concluded that he was dealing with a new metal, which he named manaccanite in honor of the parish of Mannacan.
Having discovered a new metal, Gregor returned to his pastoral duties.
Little more happens in our story until 1795, when the well-known German chemist Martin Klaproth experienced the thrill of discovering a new metallic element. Klaproth called the new metal titanium, after the Titans, the sons of the Earth goddess in Greek mythology.
Klaproth discovered titanium in the mineral rutile, from Boinik, Hungary. Just like Gregor’s calx, the rutile was a red color. In 1797 Klaproth read Gregor’s account from 1791 and realized that the red oxide in which he had found titanium and the red oxide in which Gregor had found manaccanite were in fact the same; titanium and maccanite were the same element and Gregor was the element’s true discoverer.
Gregor may have beaten Klaproth to the new metal, but scientists preferred Klaproth’s ‘titanium’ to Gregor’s ‘manaccanite.’
Obtaining a sample of pure titanium proved to be much harder than discovering it.
Many scientists tried, but it took 119 years from its discovery until 99.9% pure titanium was isolated in 1910 by metallurgist Matthew Hunter in Schenectady, New York, who heated titanium (IV) chloride with sodium to red-heat in a pressure cylinder.
In 1936, the Kroll Process (heating titanium (IV) chloride with magnesium) made the commercial production of titanium possible. By 1948 worldwide production had reached just 3 tons a year.
By 1956, however, scientists and engineers had realized titanium’s properties were highly desirable and worldwide production had exploded to 25,000 tons a year.
The 2011 forecast for worldwide production of titanium metal using the Kroll process was 223,000 metric tons.
Discovery of Magnesium
Magnesium and calcium were once thought to be the same substance. In 1755 Scottish chemist Joseph Black showed by experiment that the two were different. Black wrote:
“We have already shewn by experiment, that magnesia alba [magnesium carbonate] is a compound of a peculiar earth and fixed air.”
Magnesium was first isolated by Sir Humphrey Davy in 1808, in London, England. Davy had built a large battery and used it to pass electricity through salts. In doing so, he discovered or isolated for the first time several alkali and alkali earth metals.
In magnesium’s case, Davy’s method was similar to the one he used for barium, calcium and strontium.
Davy made a paste of moist magnesium oxide and red mercury oxide. )
He made a depression in the paste and placed about 3.5 grams of mercury metal there to act as the negative electrode. He used platinum as the positive electrode. Davy did the experiment under naphtha (a liquid hydrocarbon under which he had found he could safely store potassium and sodium).
When electricity was passed through the paste, a magnesium-mercury amalgam formed at the mercury electrode. (In later experiments Davy used moist magnesium sulfate instead of the oxide and obtained the amalgam much faster.)
The mercury was then removed from the amalgam by heating to leave magnesium metal.
In a lecture to the Royal Society in June 1808, Davy described how the magnesium he obtained was not pure because of difficulties in removing the mercury entirely from the magnesium. He was, however, able to observe that in air the metal turned into a white powder, gaining weight as it reacted with oxygen and returned to its oxide form.
Davy thought the logical name for the new metal was ‘magnesium’ but instead called it ‘magnium.’
He thought the name ‘magnium’ was, “objectionable, but magnesium has been already applied to metallic manganese…”
By 1812, Davy had changed his mind, following the “candid criticisms of some philosophical friends,” and the new metal became known as magnesium, while metallic manganese became known as… manganese.
Magnesium’s name is derived from magnesia, which Davy used in his experiment. Magnesia is the district of Thessaly in Greece where magnesia alba [magnesium carbonate] was found.
In France, in 1830, Antoine Bussy published his work showing how pure magnesium metal could be obtained. Bussy had read Friedrich Wöhler’s 1828 publication of how he had produced pure aluminum by reacting aluminum chloride with potassium. By analogy, Bussy thought he could do something similar to produce pure magnesium from magnesium chloride; he was correct.
Under red heat he reacted magnesium chloride with potassium vapor and obtained pure magnesium. He wrote, “The metal is silvery white, very brilliant, very malleable, flattens into flakes under a hammer… dilute acids attack the metal, releasing hydrogen.”
Discovery of Calcium
People have used calcium’s compounds for thousands of years – in cement, for example.
Limestone [calcium carbonate] was called calx by the Romans. The Romans heated calx, driving off carbon dioxide to leave calcium oxide. To make cement, all you have to do is mix calcium oxide with water. The Romans built vast amphitheaters and aqueducts using calcium oxide cement to bond stones together.
Despite the long history of calcium’s compounds, the element itself was not discovered until electricity was available for use in experiments.
Calcium was first isolated by Sir Humphry Davy in 1808 in London. In a lecture to the Royal Society in June 1808, Davy described his experiments that year, which produced tiny amounts of metal, at best. He could not find any way to produce more calcium metal until a letter from Jöns Berzelius in Stockholm pointed him in the right direction.
Davy learned that Berzelius and Magnus Pontin had used a battery to decompose calcium oxide at a mercury electrode and they had obtained an amalgam of mercury and calcium. (Berzelius, the great Swedish chemist, exchanged a great deal of information with Davy. Berzelius had earlier learned from Davy that potassium could be dissolved in mercury to form an amalgam. Berzelius had extended the method.)
Davy made a paste of slaked lime [calcium oxide, slightly moistened to form calcium hydroxide] and red oxide ofmercury [mercury (II) oxide].
He made a depression in the paste and placed about 3.5 grams of mercury metal there to act as an electrode. Platinum was used as the counter electrode. Davy carried out the experiment under naptha (a liquid hydrocarbon under which he had found he could safely store potassium and sodium).
When electricity was passed through the paste, a calcium-mercury amalgam formed at the mercury electrode.
Davy removed the mercury by distillation to reveal a new element: calcium.
Davy used the same procedure to isolate strontium,barium, and magnesium.
He named the metal calcium because of its occurrence in calx.
Discovery of Potassium
In 1806 English chemist Sir Humphry Davy discovered that chemical bonding was electrical in nature and that he could use electricity to split substances into their basic building blocks – the chemical elements.
In 1807 he isolated potassium for the first time at the Royal Institution, London. He electrolyzed dried potassium hydroxide (potash) which he had very slightly moistened by exposing it to the moist air in his laboratory. The electrolysis was powered by the combined output of three large batteries he had built.
When he applied a voltage from his batteries to the potassium hydroxide, he found globules “having a high metallic lustre” collected at the negatively charged electrode.
Edmund Davy, who assisted in the experiment, described Sir Humphry Davy’s reaction to the production of potassium metal, his Eureka moment:
“… when the minute globules of potassium burst through the crust of potash, and take fire as they entered the atmosphere, he could not contain his joy – he actually danced about the room in ecstatic delight; some little time was required for him to compose himself sufficiently to continue the experiment.”
Potassium was the first metal to be isolated by electrolysis.
Davy was astonished at the new metal’s low density, observing that it floated on oil – something no other metal would do. He placed a piece of potassium in water and observed that the water, “decomposes it with great violence, an instantaneous explosion with brilliant flame. He also (bravely) added potassium to hydrochloric acid and saw it burn with a bright red flame.
The name potassium is from the English word ‘potash’, originally meaning an alkali extracted with water in a pot of ash of burned wood or tree leaves.
Potassium’s symbol K comes from ‘kalium’ the name of the element in Germany and Scandinavia.
Just a few days after isolating potassium, Davy isolatedsodium for the first time using the same method.
Discovery of Sodium
In 1806 Sir Humphry Davy discovered that chemical bonding was electrical in nature and that he could use electricity to split substances into their basic building blocks – the chemical elements.
In 1807, at the Royal Institution, London, a few days after isolating potassium for the first time, he isolated sodium for the first time by electrolysis of dried sodium hydroxide, which had been very slightly moistened.
The electrolysis was powered by the combined output of three large batteries he had built.
Davy noted that the metal which formed at the wire electrode he placed in the sodium hydroxide was a liquid, but became solid on cooling and “appeared to have the lustre of silver.”
“It is exceedingly malleable and is much softer than any of the common metallic substances… this property does not diminish when it is cooled to 32 oF (0 oC).”
Davy also noted that, when added to water, sodium decomposed the water, releasing hydrogen.
He asked whether the new substance should be classed as a metal and noted that most other scientists thought it should, despite the fact that its density was much lower than the other metals then known:
“…for amongst the metals themselves there are remarkable differences in this respect, platina [we now call it platinum] being nearly four times as heavy astellurium.”
He named the new metal sodium, because he had used caustic soda or, more simply, soda, as his source of the element.
In Germany caustic soda was known as natronlauge and L. W. Gilbert suggested the new element should be called natronium.
J. J. Berzelius preferred the shorter natrium, from which we get the chemical symbol for sodium, Na.
Discovery of Lithium
Lithium was discovered by Johan Arfvedson in 1817 in Stockholm, Sweden, during an analysis of petalite (LiAlSi4O10).
He found the petalite contained “silica, alumina and an alkali.” (1)
The new alkali metal in the petalite had unique properties.
It required more acid to neutralize it than sodium and its carbonate was only sparingly soluble in water – unlike sodium carbonate.
The new alkali differed from potassium because it did not give a precipitate with tartaric acid.
Arfvedson tried to produce a pure sample of the new metal by electrolysis, but he was unsuccessful; the battery he used was not powerful enough. (2)
The pure metal was isolated the following year by both Swedish chemist William Brande and English chemist Humphry Davy working independently.
Davy obtained a small quantity of lithium metal by electrolysis of lithium carbonate. (3)
He noted the new element had a red flame color somewhat like strontium and produced an alkali solution when dissolved in water.
In days less safety-conscious than the present, Brande said of lithium, “its solution tastes acrid like the other fixed alkalies.” (4)
By 1855 Robert Bunsen and Augustus Matthiessen were independently producing the metal in large quantities by electrolysis of molten lithium chloride.
Lithium’s name is derived from the Greek word ‘lithos’ meaning, ‘stone.’
گزارش جلسه 15 آذر 1391
در تاریخ 15 آذر جلسه ای برگزار شد که در آن موارد زیر بحث شد
1.ساخت مهر مخصوص انجمن
2. صدور کارت شناسایی ویژه اعضا
3.شرح وظایف اعضای انجمن
4. رتبه بندی اعضا براساس میزان فعالیت در وبلاگ
5. ارائه کار شاخص ویژه اعضای انجمن ساخت نرم افزار فرهنگ لفت کتاب درسی، ساخت بازی و سرگرمی، ساخت نرم افزار نمونه سوالات طبقه بندی شده با پاسخ
