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| Emerald |
Amethyst is a mineral with a beautiful green color, which are responsible for small amounts of chromium and sometimes vanadium and iron. Of course, he arouses the greatest interest as part of the ornaments and jewelry. However, the long, long time ago, in the eighteenth century also attracted chemists who wanted to learn its secrets and discover what elements constitute the composition of this mineral. On the way the various examinations and tests assigned szmaragdowi (and yet another minerałowi, as I say later;) the composition of the corresponding aluminum krzemianowi limestone. One of the researchers, who came to this conclusion was a French chemist Louis Nicolas Vauquelin . However, the further course of events has meant that the time has come where Vauquelin had completely verify the results of their research ...
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| René Just Haüy |
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| Louis Nicolas Vauquelin |
Vauquelin was a close friend in the person René Just Haüya . Haüy is referred to as the "father" crystallography. Among others, he formulated the so-called in 1784. sections of the law of rational relations (right Haüya) saying that double the value of the severed sections of the relations of intersecting edges of the crystal by any two of its walls and HKL H'K'L ' ie, a / a ': b / b', a / a ': c / c', b / b ': c / c', expressed rational numbers. Haüy made many discoveries in the field of crystallography, among others. first described the phenomenon piroelektryczności. Vauquelin told Haüyemu about their problems with emerald, intrigues scientist so that he decided to carry out a crystallographic study. Finally Haüy Vauquelin insisted that he repeated his analysis further. French chemist and had already had so many classes, among other things he discovered in Siberia derived from mineral element krokoicie chrome [krokoit ( called red lead ) is PbCrO 4 ]. Vauquelin spoke with due diligence to analyze the emerald, which the sample came from Peru;) moved a small portion of the solution, then carefully add KOH to precipitate Al (OH) 3 . When the Frenchman began to add an excess of KOH, it turned out that the system remained solid nieroztworzonego much - a fact which is overlooked by previous experiments:) That was the Vauquelina precipitate isolated from the solution and dissolved in acid, converted into salts, which are examined in detail the chemist . These salts have a sweet taste, making the newly discovered oxide of an unknown element was named glucina ( Lat . sweet ). Vauquelin presented their findings in the scientific community, these were also confirmed, among others by a German chemist JF Gmelin. The discovery of a new element has become a reality! But there was still the question of the name of the new item. Chemists rather corresponded to the name suggested by a French scientist, what else can you define an element as sweet?;) Moreover, this name was not on the original expression - a German chemist Klaproth had Vauquelinowi try yttrium salt, which also have a sweet taste; ) What ultimately was given the name "słitaśnemu" root? Remember that other minerals, which I mentioned at the beginning? Was studied in parallel with the emerald of the two French researchers. This mineral is called beryllium. chemical formula of beryllium is Be 3 Al 2 (SiO 3 ) 6 (plus additives). Interestingly, in France in the 50's of last century could be found to determine glucinium for beryllium.
Obtaining beryllium - History
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| metallic beryllium |
Uncover but does not always receive. Obtaining a free, metallic beryllium is due to a certain doctor and pharmacist, professor of chemistry at École de Pharmacie in Paris, who was called Antoine-Alexandre-Brutus Bussy. And it was the year 1827 ... Bussy mixed beryllium chloride ( Becla 2 ) and metallic potassium in a platinum crucible which was covered with age is also made of platinum crucible and then warmed over a spirit lamp. The reaction that followed was so violent that the whole melting pot began to glow strongly. After the reaction the residue Bussy water industry, while on the bottom left gray powder, which is elemental beryllium;) Here is the equation of reaction:
Becla 2 + 2 K → Be ↓ + 2 KCl
Around the same time, completely independently, the same reaction carried out well-known to you Friedrich Wöhler ;) The beryllium by electrolysis received around 1900, another French chemist, Paul Lebeau . He put the electrolysis of molten mixture KF and BeF 2 placed in a nickel crucible, thereby generating beryllium metal with a purity above 99.5 % This process, however, was not profitable, especially for production of larger amounts of the element, so same as the pure beryllium and secretion by the thermal decomposition of Bei 2 . Until the second half of the last 50 years of age were not properly developed cost-effective process for the production of Be-free.
Obtaining beryllium - today
now replaced by a beryllium two methods: by reducing BeF 2 metallic magnesium or by electrolysis of molten Becla 2 . Starting substrate to achieve these halides is a mineral beryl. Let us turn to the beginning of receiving fluoride. Beryl is converted into beryllium hydroxide Be (OH) 2 first subjecting the mineral melt in the presence of flux at 770 of C and the reaction created in this way tetrafluoroberylanu sodium with sodium hydroxide:
Be 3 Al 2 (Si 6 About 18 ) + 2 In 2 [SIF 6 ] + In 2 CO 3 → 3 In 2 [BEF 4 ] + Al 2 The 3 + 8 Not 2 + CO 2
And 2 [BEF 4 ] + 2 NaOH → Be (OH) 2 + 4 NaF
resulting hydroxide is dissolved in an aqueous solution of ammonium hydrogen fluoride:
Be (OH) 2 + 2 (NH 4 ) [HF 2 ] → (NH 4 ) 2 [BeF 4 ] + 2 H 2 About
obtained in this way tetrafluoroberylan ammonium crystallized and then subjected to thermal decomposition at 1000 of C
(NH 4 ) 2 [BeF 4 ] → BeF 2 + 2 NH 3 + 2 HF
beryllium fluoride with magnesium reduced at 900 of C and free of beryllium, which is at 1300 of C melts to solid metal. ;
BeF 2 + Mg → Be + MgF 2
The beryllium chloride are prepared by dehydration Be (OH) 2 to Beo and then act on beryllium oxide with carbon in a stream of chlorine gas at a temperature of about 500-600 of C :
Be (OH) 2 → Live + H 2 O
Live + C + Cl 2 → BeCl 2 + CO
Molten Becla 2 conducts electricity very poorly, because electrolysis is subjected to a mixture containing equal amounts of Becla 2 and NaCl .
Similarity of beryllium to aluminum
Due to the small atomic radius and ionic beryllium, high energy ionization, a very high ratio of charge / radius for Be 2 + (similar to the values \u200b\u200bfor Al 3 + ) and associated with the stronger polarization of anions (favoring covalent bonding character) has called beryllium. diagonal similarity to aluminum. Here are some examples pointing to the intriguing relationship;)
strong acidity [Be (H 2 O) 4 ] 2 + . Be 2 + strongly polarizes an already strongly polarized OH bond, which leads to easy loss of the proton:
[Be(H 2 O) 4 ] 2+ + H 2 O ⇌ [Be(H 2 O) 3 (OH)] + + [H 3 O] +
[Al (H 2 O) 6 ] 3 + is also strongly acidic (pK a = 5.0). Cations [Be (H 2 O) 4 ] 2 + may be subject to condensation in aqueous solutions to complex cationic complexes zwierających bridging Be-O-Be, in which also resemble akwajony aluminum, for example:
4 [Be (H 2 O) 4 ] 2+ + 2 H 2 O ⇌ 2 [(H 2 O) 3 Be-O-Be(H 2 O) 3 ] 2+ + 4 [H 3 O] +
Be and Al react with the secretory alkaline hydrogen. Oxides and hydroxides of both these elements are amphoteric.
Beo + 2 KOH + H 2 About → K 2 [Be (OH) 4 ]
Be (OH) 2 + 2 KOH → K 2 [Be (OH) 4 ]
BeCl 2 and AlCl 3 are reactive solids, steaming in moist air (HCl formed) and having polymeric structure with bridging chlorkowymi. Both Be and Al form a complex halide anions, among others. complex fluoride anions [BeF 4 ] 2 - and [AlF 6 ] 3 - . Other metals two groups do not form stable complexes of fluoride.
Beo (like Al 2 About 3 ) is extremely tough and non-volatile, has a very high melting point (2507 of C).
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