Of the element with atomic number 31, most readers remember only that it is one of the three elements predicted and described in most detail by D.I. Mendeleev, and that gallium is a very fusible metal: to turn it into a liquid, the heat of the palm is enough.
However, gallium is not the most fusible of metals (even if you do not count mercury). Its melting point is 29.75°C, while cesium melts at 28.5°C; only cesium, like any alkali metal, you cannot take in your hands, therefore, in the palm of your hand, naturally, it is easier to melt gallium than cesium.
Sing a story about element #31, we deliberately started by mentioning something that is known to almost everyone. Because this "known" needs some explanation. Everyone knows that gallium was predicted by Mendeleev and discovered by Lecoq de Boisbaudran, but not everyone knows how the discovery happened. Almost everyone knows that gallium is fusible, but almost no one can answer the question why it is fusible.
How was gallium discovered?
The French chemist Paul Emile Lecoq de Boisbaudran went down in history as the discoverer of three new elements: gallium (1875), samarium (1879) and dysprosium (1886). The first of these discoveries brought him fame.
At that time, outside of France, he was little known. He was 38 years old, he was mainly engaged in spectroscopic research. Lecoq de Boisbaudran was a good spectroscopist, and this ultimately led to success: he discovered all three of his elements by spectral analysis.
In 1875, Lecoq de Boisbaudran investigated the spectrum of zinc blende brought from Pierrefitte (Pyrenees). It was in this spectrum that a new violet line (wavelength 4170 Å) was discovered. The new line indicated the presence of an unknown element in the mineral, and, quite naturally, Lecoq de Boisbaudran made every effort to isolate this element. This was not easy to do: the content of the new element in the ore was less than 0.1%, and in many ways it was similar to zinc*. After lengthy experiments, the scientist managed to get a new element, but in a very small amount. So small (less than 0.1 g) that Lecoq de Boisbaudrap could not fully study its physical and chemical properties.
* How gallium is obtained from zinc blende is described below.
The announcement of the discovery of gallium - so in honor of France (Gallia - its Latin name) a new element was named - appeared in the reports of the Paris Academy of Sciences.
This message was read by D.I. Mendeleev recognized ekaaluminum, which he had predicted five years earlier, in gallium. Mendeleev immediately wrote to Paris. “The method of discovery and isolation, as well as the few properties described, suggest that the new metal is nothing more than ekaaluminum,” his letter said. It then repeated the predicted properties for that element. Moreover, never holding a grain of gallium in his hands, without seeing it in his eyes, the Russian chemist claimed that the discoverer of the element was mistaken, that the density of the new metal cannot be equal to 4.7, as Lecoq de Boisbaudran wrote, - it must be more about 5.9...6.0 g/cm3!
Strange as it may seem, but the first of his affirmative, "strengthening" ones learned about the existence of the periodic law only from this letter. He again isolated and carefully purified the gallium grains in order to verify the results of the first experiments. Some historians of science believe that this was done in order to shame the self-confident Russian "predictor". But experience has shown the opposite: the discoverer was mistaken. Later he wrote: "It is not necessary, I think, to point out the exceptional importance that the density of a new element has in relation to the confirmation of Mendeleev's theoretical views."
The other properties of element No. 31 predicted by Mendeleev almost exactly coincided with the experimental data. "Mendeleev's predictions came true with minor deviations: ekaaluminum turned into gallium." This is how Engels characterizes this event in Dialectics of Nature.
Needless to say, the discovery of the first element predicted by Mendeleev significantly strengthened the position of the periodic law.
Why is gallium fusible?
Predicting the properties of gallium, Mendeleev believed that this metal should be fusible, since its analogues in the group - aluminum and indium - also do not differ in refractoriness.
But the melting point of gallium is unusually low, five times lower than that of indium. This is explained by the unusual structure of gallium crystals. Its crystal lattice is formed not by individual atoms (as in "normal" metals), but by diatomic molecules. Ga 2 molecules are very stable; they are preserved even when gallium is converted to a liquid state. But these molecules are connected to each other only by weak van der Waals forces, and very little energy is needed to break their connection.
Some more properties of element No. 31 are associated with the diatomicity of molecules. In the liquid state, gallium is denser and heavier than in the solid state. The electrical conductivity of liquid gallium is also greater than that of solid gallium.
Outwardly - most of all on tin: a silvery-white soft metal, it does not oxidize and does not tarnish in air.
And in most chemical properties, gallium is close to aluminum. Like aluminum, there are three electrons in the outer orbit of a gallium atom. Like aluminum, gallium easily, even in the cold, interacts with halogens (except iodine). Both metals readily dissolve in sulfuric and hydrochloric acids, both react with alkalis and give amphoteric hydroxides. Dissociation constants of reactions
Ga(OH) 3 → Ga 3+ + 3OH -
H 3 GaO 3 → 3H + + GaO 3– 3
are quantities of the same order.
There are, however, differences in the chemical properties of gallium and aluminum.
With dry oxygen, gallium is noticeably oxidized only at temperatures above 260 ° C, and aluminum, if it is deprived of its protective oxide film, is oxidized by oxygen very quickly.
With hydrogen, gallium forms hydrides similar to boron hydrides. Aluminum, on the other hand, can only dissolve hydrogen, but not react with it.
And gallium is similar to graphite, quartz, water.
On graphite - the one that leaves a gray mark on paper.
On quartz - electrical and thermal anisotropy.
The electrical resistance of gallium crystals depends on which axis the current flows along. The ratio of maximum to minimum is 7 - more than any other metal. The same is true for the coefficient of thermal expansion.
Its values in the direction of three crystallographic axes (rhombic gallium crystals) are related as 31:16:11.
And gallium is similar to water in that it expands when it hardens. The increase in volume is noticeable - 3.2%.
Already one combination of these conflicting similarities speaks of the unique individuality of element No. 31.
In addition, it has properties that are not inherent in any element. Molten, it can remain supercooled for many months below its melting point. It is the only metal that remains a liquid over a wide temperature range from 30 to 2230°C, and its vapor volatility is minimal. Even in a high vacuum, it only noticeably evaporates at 1000°C. Gallium vapors, unlike solid and liquid metals, are monatomic. The Ga 2 → 2Ga transition requires a lot of energy; this explains the difficulty of evaporating gallium.
The large temperature range of the liquid state is the basis of one of the main technical applications of element No. 31.
What is gallium good for?
Gallium thermometers allow, in principle, to measure temperatures from 30 to 2230°C. Gallium thermometers are now available for temperatures up to 1200°C.
Element No. 31 goes to the production of low-melting alloys used in signaling devices. An alloy of gallium and indium melts already at 16°C. It is the most fusible of all known alloys.
As an element of group III, which contributes to the enhancement of "hole" conductivity in a semiconductor, gallium (with a purity of at least 99.999%) is used as an additive to germanium and silicon.
Intermetallic compounds of gallium with elements of the V group - antimony and arsenic - themselves have semiconductor properties.
The addition of gallium to the glass mass makes it possible to obtain glasses with a high refractive index of light rays, and glasses based on Ga 2 O 3 transmit infrared rays well.
Liquid gallium reflects 88% of the light falling on it, solid - a little less. Therefore, gallium mirrors are very easy to manufacture - a gallium coating can even be applied with a brush.
Sometimes the ability of gallium to wet solid surfaces well is used, replacing mercury in diffusion vacuum pumps. Such pumps “keep” the vacuum better than mercury pumps.
Attempts have been made to use gallium in nuclear reactors, but the results of these attempts can hardly be considered successful. Not only does gallium quite actively capture neutrons (capture cross section of 2.71 barns), it also reacts at elevated temperatures with most metals.
Gallium did not become an atomic material. True, its artificial radioactive isotope 72 Ga (with a half-life of 14.2 hours) is used to diagnose bone cancer. Gallium-72 chloride and nitrate are adsorbed by the tumor, and by fixing the radiation characteristic of this isotope, doctors almost accurately determine the size of foreign formations.
As you can see, the practical possibilities of element No. 31 are quite wide. It has not yet been possible to use them completely due to the difficulty of obtaining gallium, a rather rare element (1.5 10 -3% of the weight of the earth's crust) and very scattered. Few native minerals of gallium are known. Its first and most famous mineral, gallite CuGaS 2, was discovered only in 1956. Later, two more minerals were found, which were already quite rare.
Usually, gallium is found in zinc, aluminum, iron ores, as well as in coal - as an insignificant impurity. And what is characteristic: the more this impurity, the more difficult it is to extract it, because there is more gallium in the ores of those metals (aluminum, zinc) that are close to it in properties. The main part of terrestrial gallium is enclosed in aluminum minerals.
The extraction of gallium is an expensive “pleasure”. Therefore, element #31 is used in smaller quantities than any of its neighbors in the periodic table.
It is possible, of course, that science in the near future will discover something in gallium that will make it absolutely necessary and irreplaceable, as happened with another element predicted by Mendeleev, germanium. Just 30 years ago, it was used even less than gallium, and then the “era of semiconductors” began ...
Search for patterns
The properties of gallium were predicted by D.I. Mendeleev five years before the discovery of this element. The ingenious Russian chemist built his predictions on the patterns of changes in properties by groups of the periodic system. But for Lecoq de Boisbaudran, the discovery of gallium was not a happy accident either. A talented spectroscopist, as early as 1863 he discovered regularities in the change in the spectra of elements with similar properties. Comparing the spectra of indium and aluminum, he came to the conclusion that these elements may have a "brother" whose lines would fill the gap in the short-wavelength part of the spectrum. It was this missing line that he was looking for and found in the spectrum of zinc blende from Pierrfit.
For comparison, we present a table of the main properties predicted by D.I. Mendeleev ekaaluminum and gallium discovered by Lecoq de Boisbaudran.
| Ekaaluminum | Gallium |
| Atomic weight about 68 | Atomic weight 69.72 |
| Must be low melting | Melting point 29.75°C |
| Specific gravity close to 6.0 | Specific gravity 5.9 (solid) and 6.095 (liquid) |
| Atomic volume 11.5 | Atomic volume 11.8 |
| Must not oxidize in air | Slightly oxidized only at spirit-red heat |
| Should decompose water at high temperature | Decomposes water at high temperature |
| Compound formulas: EaCl 3 Ea 2 O 3, Ea 2 (SO 4) 3 | Compound formulas: GaCl 3, Ga 3 O 3, Ga 2 (SO 4) 3 |
| Should form alum Ea 2 (SO 4) 3 Me 2 SO 4 24H 2 O, but more difficult than aluminum | Forms alum composition (NH 4) Ga (SO 4) 2 12H 2 O |
| The oxide Ea 2 O 3 should be easily reduced and give a metal more volatile than Al, and therefore it can be expected that eka aluminum will be discovered by spectral analysis. | Gallium is easily reduced from oxide by calcination in a stream of hydrogen, discovered using spectral analysis |
Wordplay?
Some historians of science see in the name of element No. 31 not only patriotism, but also the indiscretion of its discoverer. It is generally accepted that the word "gallium" comes from the Latin Gallia (France). But if you wish, in the same word you can see a hint of the word "rooster"! In Latin, "rooster" is gallus, in French - le coq. Lecoq de Boisbaudran?
Depending on age
In minerals, gallium often accompanies aluminum. Interestingly, the ratio of these elements in the mineral depends on the time of formation of the mineral. In feldspars, one atom of gallium falls on 120 thousand aluminum atoms. In nephelines formed much later, this ratio is already 1:6000, and in even “younger” petrified wood it is only 1:13.
First patent
The first patent for the use of gallium was taken 60 years ago. Element No. 31 wanted to be used in electric arc lamps.
Displaces sulfur, defends itself with sulfur
The interaction of gallium with sulfuric acid is interesting. It is accompanied by the release of elemental sulfur. In this case, sulfur envelops the surface of the metal and prevents its further dissolution. If, however, the metal is washed with hot water, the reaction will resume, and will continue until a new “skin” of sulfur grows on the gallium.
Bad influence
Liquid gallium interacts with most metals, forming alloys and intermetallic compounds with rather low mechanical properties. That is why contact with gallium leads many structural materials to a loss of strength. Beryllium is the most resistant to the action of gallium: at temperatures up to 1000 ° C, it successfully resists the aggressiveness of element No. 31.
And oxide too!
Insignificant additions of gallium oxide noticeably affect the properties of oxides of many metals. So, the admixture of Ga 2 O 3 to zinc oxide significantly reduces its sintering. But the solubility of zinc in such an oxide is much greater than in pure. And in titanium dioxide, when Ga 2 O 3 is added, the electrical conductivity drops sharply.
How is gallium obtained
Industrial deposits of gallium ores have not been found in the world. Therefore, gallium has to be extracted from zinc and aluminum ores, which are very poor in it. Since the composition of the ores and the content of gallium in them are not the same, the methods for obtaining element No. 31 are quite diverse. For example, we will tell you how gallium is extracted from zinc blende, a mineral in which this element was first discovered.
First of all, zinc blende ZnS is fired, and the resulting oxides are leached with sulfuric acid. Together with many other metals, gallium goes into solution. Zinc sulfate predominates in this solution - the main product that must be purified from impurities, including gallium. The first stage of purification is the precipitation of the so-called iron sludge. With the gradual neutralization of the acid solution, this sludge precipitates. It contains about 10% aluminum, 15% iron and (which is most important for us now) 0.05 ... 0.1% gallium. To extract gallium, the sludge is leached with acid or caustic soda - amphoteric gallium hydroxide. The alkaline method is more convenient, since in this case it is possible to make equipment from less expensive materials.
Under the action of alkali, aluminum and gallium compounds go into solution. When this solution is carefully neutralized, gallium hydroxide precipitates. But part of the aluminum also precipitates. Therefore, the precipitate is dissolved again, now in hydrochloric acid. It turns out a solution of gallium chloride, contaminated mainly with aluminum chloride. These substances can be separated by extraction. Ether is poured in and, unlike AlCl 3 , GaCl 3 almost completely passes into the organic solvent. The layers are separated, the ether is distilled off, and the resulting gallium chloride is once again treated with concentrated caustic soda to precipitate and separate the iron impurity from gallium. From this alkaline solution, metallic gallium is obtained. Obtained by electrolysis at a voltage of 5.5 V. Gallium is deposited on a copper cathode.
gallium and teeth
For a long time, gallium was thought to be toxic. Only in recent decades has this misconception been refuted. Low-melting gallium interested dentists. Back in 1930, it was first proposed to replace mercury with gallium in dental filling compositions. Further studies both here and abroad confirmed the promise of such a replacement. Mercury-free metal fillings (mercury replaced by gallium) are already used in dentistry.
The chemical element gallium is practically not found in nature in free form. It exists in impurities of minerals, from which it is difficult to separate it. Gallium is considered a rare substance, some of its properties are not fully understood. However, it is used in medicine and electronics. What is this element? What properties does it have?
Gallium - metal or non-metal?
The element belongs to the thirteenth group of the fourth period. It is named after the historical region - Gaul, of which France was a part - the birthplace of the discoverer of the element. The symbol Ga is used to denote it.
Gallium is included in the group of light metals along with aluminum, indium, germanium, tin, antimony and other elements. As a simple substance, it is fragile and soft, has a silvery-white color with a slight bluish tint.
Discovery history
Mendeleev "predicted" gallium, leaving a place for it in the third group of the periodic table (according to the outdated system). He roughly named its atomic mass and even predicted that the element would be discovered spectroscopically.
A few years later, the metal was discovered by the Frenchman Paul Emile Lecoq. In August 1875, a scientist was studying the spectrum from a deposit in the Pyrenees and noticed new purple lines. The element was named gallium. Its content in the mineral was extremely small and Lecoq managed to isolate only 0.1 grams. The discovery of the metal was one of the confirmations of the correctness of Mendeleev's prediction.
Physical properties
Gallium metal is very ductile and fusible. At low temperatures, it is in a solid state. To turn it into a liquid, a temperature of 29.76 degrees Celsius or 302.93 Calvin is sufficient. You can melt it by holding it in your hand or dropping it into a hot liquid. Too high temperatures make it very aggressive: at 500 degrees Celsius and above, it is able to corrode other metals.
The crystal lattice of gallium is formed by diatomic molecules. They are very stable, but weakly interconnected. It takes very little energy to break their bond, so gallium becomes liquid without difficulty. It is five times more fusible than indium.
In the liquid state, the metal is denser and heavier than in the solid state. In addition, it conducts electricity better. Under normal conditions, its density is 5.91 g/cm³. The metal boils at -2230 degrees Celsius. When solidified, it expands by approximately 3.2%.
Chemical properties
In many chemical properties, gallium is similar to aluminum, but exhibits less activity and reactions with it are slower. It does not react with air, instantly forming an oxide film that prevents its oxidation. It does not react to hydrogen, boron, silicon, nitrogen and carbon.
The metal interacts well with almost any halogen. It reacts with iodine only when heated; it reacts with chlorine and bromine even at room temperature. In hot water, it begins to displace hydrogen, forms salts with mineral acids, and also releases hydrogen.
With other metals, gallium is able to form amalgams. If liquid gallium is dropped onto a solid piece of aluminum, it will begin to penetrate into it. Invading the crystal lattice of aluminum, the liquid substance will make it brittle. Within a few days, a solid metal bar can be crushed by hand, without much effort.
Application
In medicine, gallium metal is used to fight tumors and hypercalcemia, it is also suitable for radioisotope diagnosis of bone cancer. However, preparations containing the substance may cause side effects such as nausea and vomiting.
Gallium metal is also used in microwave electronics. It is used for the manufacture of semiconductors and LEDs, as a piezo material. Metal adhesives are obtained from an alloy of gallium with scandium or nickel. In an alloy with plutonium, it plays the role of a stabilizer and is used in nuclear bombs.
Glasses with this metal have a high refractive index, and its oxide Ga 2 O 3 allows the glass to transmit infrared rays. Pure gallium can be used to make simple mirrors, as it reflects light well.
Distribution and deposits of gallium
Where to get gallium? Metal can be easily ordered online. Its cost ranges from 115 to 360 dollars per kilogram. The metal is considered rare, it is very dispersed in the earth's crust and practically does not form its own minerals. Since 1956, all three have been found.
Often gallium is found in the composition of zinc, iron, Its impurities are found in coal, beryl, garnet, magnetite, tourmaline, feldspar, chlorites and other minerals. On average, its content in nature is about 19 g/t.
Most gallium is found in substances that are close to it in composition. Because of this, it is difficult and expensive to extract from them. The metal's own mineral is called gallite with the formula CuGaS 2 . It also contains copper and sulfur.
Impact on a person
Little is known about the biological role of the metal and its effects on the human body. In the periodic table, it is next to the elements that are vital to us (aluminum, iron, zinc, chromium). There is an opinion that, as an ultramicroelement, gallium is part of the blood, accelerating its flow and preventing the formation of blood clots.
One way or another, a small amount of the substance is contained in the human body (10 -6 - 10 -5%). Gallium enters it together with water and agricultural food. It lingers in the bone tissue and liver.
Gallium metal is considered low-toxic or conditionally toxic. Upon contact with the skin, small particles remain on it. It looks like a gray dirty spot that is easily removed with water. The substance does not leave burns, but in some cases it can cause dermatitis. It is known that a high content of gallium in the body causes disorders in the liver, kidneys and nervous system, but this requires a very large amount of metal.
He formulated his periodic law and compiled the periodic table, many metals were not yet known to science.
This, however, did not prevent the chemist from building his periodic table, leaving empty cells for elements not yet discovered. These "blank spots" were soon filled. One of such elements predicted by Mendeleev will be discussed today.
Meet: gallium, number 31 in the table. The third group is a low-melting metal, similar in properties to aluminum and silicon. Mendeleev not only described the properties of this metal in sufficient detail, but also indicated its atomic weight with almost 100% accuracy.
Discovery and origin of the name
Gallium was discovered and isolated as a simple substance by the French chemist Paul Emile Lecoq de Boisbaudran. It happened in 1875, when the scientist studied samples of zinc blende brought from the Pyrenees. The studies were carried out by spectroscopy, and the scientist noticed a purple line in the spectrum of the ore, indicating the presence of an unknown element in the mineral.
The isolation of the element in its pure form required a lot of work, since its content in the ore was less than 0.1%. In the end, Lecoq de Boisbaudran managed to obtain less than 0.1 gram of pure substance and study it. The element discovered by the Frenchman turned out to be in many respects similar in properties to zinc.
At the next meeting of the Paris Academy of Sciences, held on September 20, 1875, a letter from Lecoq de Boisbaudran was read, which reported on the discovery of a new element and the study of its properties. The chemist also reported that he named the newly discovered element in honor of France, according to its Latin name - Gallia (Gallia).
When Mendeleev read the published report on this discovery, he noted that the description of the properties of the new element coincided almost exactly with the description of ekaaluminum he had previously predicted. Mendeleev was not slow to report this to Lecoq de Boisbaudran, pointing out that the density of the new metal was determined incorrectly and should be 5.9-6.0, not 4.7 g/cm3. A thorough check showed that Mendeleev was right.
Gallium mining
In nature, gallium does not form large deposits. In some minerals, gallium is contained in relatively large (for this metal): garnet, sphalerite, tourmaline, beryl, feldspars, nepheline.
The richest source of gallium is the mineral germanite, an ore composed of copper sulfide that can contain 0.5-0.7% gallium. In addition, gallium is obtained during the processing of bauxite and nepheline. Also, this metal can be obtained by processing polymetallic ores, coal.
The contaminated gallium is washed with water, then filtered through porous plates and heated under vacuum to remove volatile impurities. To obtain gallium of high purity, chemical (reactions between salts), electrochemical (electrolysis of solutions) and physical (decomposition) methods are used.
The deposits where gallium is being mined are located mainly in South-West Africa, as well as in Russia and in some of the CIS countries.
properties of gallium
Gallium is a soft, ductile, silvery metal. At low temperatures, it is in a solid state, but already melts at a temperature slightly higher than room temperature (29.8 ° C).
In general, a wide temperature range for the existence of a liquid state of this metal (from 30 to 2230 ° C) is one of the features of gallium. The chemical properties of gallium are close to those of aluminum. Due to its fusibility, transportation of gallium is carried out in plastic bags.
Before the advent of semiconductors, gallium was used to create low-melting alloys. Today, gallium is used mainly in microelectronics as part of semiconductors. Gallium nitride is used in the creation of semiconductor lasers and LEDs in the blue and ultraviolet range.
Gallium is an excellent lubricant. On the basis of gallium and nickel, gallium and scandium, metal adhesives that are very important in practical terms have been created. Gallium metal is also used to fill quartz thermometers for measuring high temperatures, replacing mercury with this metal. This is because gallium has a much higher boiling point than mercury.
Gallium is one of the most expensive metals. So in 2005, a ton of gallium cost 1.2 million US dollars on the world market. Due to its high cost and the great need for this metal, it is very important to establish its complete extraction in aluminum production and processing of coal for liquid fuel.
GALLIUM metal that melts in the hands.
Metal GALLIUM
Gallium is an element of the main subgroup of the third group of the fourth period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 31. It is designated by the symbol Ga (lat. Gallium). Belongs to the group of light metals. The simple substance gallium (CAS number: 7440-55-3) is a soft ductile metal of silver-white (according to other sources, light gray) color with a bluish tint.
Metal GALLIUM
Gallium: Melting point 29.76 °C
low toxicity, you can pick up and melt!
Material for semiconductor electronics
Gallium arsenide GaAs
A promising material for semiconductor electronics.
gallium nitride
used in the creation of semiconductor lasers and LEDs in the blue and ultraviolet range. Gallium nitride has excellent chemical and mechanical properties typical of all nitride compounds.
Isotope gallium-71
is the most important material for detecting neutrinos, and in connection with this, technology faces a very urgent task of isotope isolation from a natural mixture in order to increase the sensitivity of neutrino detectors. Since the content of 71Ga in the natural mixture of isotopes is about 39.9%, the isolation of a pure isotope and its use as a neutrino detector can increase the detection sensitivity by 2.5 times.
Chemical properties
Gallium is expensive, in 2005 a ton of gallium cost 1.2 million US dollars on the world market, and due to the high price and at the same time the great demand for this metal, it is very important to establish its complete extraction in aluminum production and coal processing at liquid fuel.
Gallium has a number of alloys that are liquid at room temperature, and one of its alloys has a melting point of 3 °C (In-Ga-Sn eutectic), but on the other hand, gallium (alloys to a lesser extent) is very aggressive to most structural materials (cracking and erosion of alloys at high temperature). For example, in relation to aluminum and its alloys, gallium is a powerful strength reducer (see adsorption strength reduction, Rehbinder effect). This property of gallium was most clearly demonstrated and studied in detail by P. A. Rebinder and E. D. Shchukin during the contact of aluminum with gallium or its eutectic alloys (liquid-metal embrittlement). As a coolant, gallium is ineffective, and often simply unacceptable.
Gallium is an excellent lubricant
On the basis of gallium and nickel, gallium and scandium, metal adhesives that are very important in practical terms have been created.
Gallium metal is also filled into quartz thermometers (instead of mercury) to measure high temperatures. This is because gallium has a much higher boiling point than mercury.
Gallium oxide is part of a number of strategically important laser materials of the garnet group - GSHG, YAG, ISGG, etc.
Of the element with atomic number 31, most readers remember only that it is one of the three elements predicted and described in most detail by D.I. Mendeleev, and that it is a very fusible metal: to turn it into a liquid, the heat of the palm is enough.
We deliberately began our story about element No. 31 by mentioning something that is known to almost everyone. Because this "known" needs some explanation. Everyone knows that gallium was predicted by Mendeleev and discovered by Lecoq de Boisbaudran, but not everyone knows how the discovery happened. Almost everyone knows that gallium is fusible, but almost no one can answer the question why it is fusible.
How was gallium discovered?
The French chemist Paul Emile Lecoq de Boisbaudran went down in history as the discoverer of three new elements: gallium (1875), samarium (1879) and dysprosium (1886). The first of these discoveries brought him fame.
At the time outside of France, he was little known. He was 38 years old, he was mainly engaged in spectroscopic research. Lecoq de Boisbaudran was a good spectroscopist, and this ultimately led to success: he discovered all three of his elements by spectral analysis.
In 1875, Lecoq de Boisbaudran investigated the spectrum of zinc blende brought from Pierrefitte (Pyrenees). It was in this spectrum that a new violet line was discovered (wavelength 4170A). The new line indicated the presence of an unknown element in the mineral, and, quite naturally, Lecoq de Boisbaudran made every effort to isolate this element. This was not easy to do: the content of the new element in the ore was less than 0.1%, and in many ways it was similar to zinc. After lengthy experiments, the scientist managed to get a new element, but in a very small amount. So small (less than 0.1 g) that Lecoq de Boisbaudran could not fully study its physical and chemical properties.
The message about the discovery of gallium - so in honor of France (Gallia - its Latin name) a new element was named - appeared in the reports of the Paris Academy of Sciences.
D. I. Mendeleev read this message and recognized in gallium the eka-aluminum he had predicted five years earlier. Mendeleev immediately wrote to Paris. "The method of discovery and isolation, as well as the few properties described, suggest that the new metal is nothing but ekaaluminum," his letter said. It then repeated the predicted properties for that element. Moreover, never holding a grain of gallium in his hands, not seeing it in his eyes, the Russian chemist claimed that the discoverer of the element was mistaken, that the density of the new metal cannot be equal to 4.7, as Lecoq de Boisbaudran wrote, it should be more, approximately 5.9-6.0 g/cm3.
Oddly enough, but about the existence of a periodicof the law, the first of its approvers, the “strengtheners”, learned only from this letter. He singled out and carefullypurified grains of gallium to check the results of the first experiments. Some historians of science believe that this was done in order to shame the self-confident Russian"predictor". But experience has shown the opposite: the discoverer was mistaken. Later he wrote: "It is not necessary, I think, to point out the exceptional importance that the density of a new element has in relation to the confirmation of Mendeleev's theoretical views."
The other properties of element No. 31 predicted by Mendeleev almost exactly coincided with the experimental data. "Mendeleev's predictions came true with minor deviations: ekaaluminum turned into gallium." This is how Engels characterizes this event in Dialectics of Nature.
Needless to say, the discovery of the first element predicted by Mendeleev significantly strengthenedposition of the periodic law.
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