The oxidation state of rubidium. Rubidium: properties, role in the body, sources of rubidium Characteristics of rubidium
RUBIDIUM, Rb (a. rubidium; n. Rubidium; f. rubidium; and. rubidio), - chemical element of group I of the periodic system of Mendeleev, atomic number 37, atomic mass 85.4678; belongs to the alkali metals. It occurs in nature as a mixture of two stable isotopes: 85 Rb (72.15%) and 87 Rb (27.85%), the latter is radioactive and, emitting a b-particle, turns into a stable isotope 87 Sr. There are also 19 artificial isotopes of rubidium.
It was discovered by the German scientists R. Bunsen and G. Kirchhoff in 1861 during a spectral study of sediment evaporated from the mineral waters of the Black Forest. Scientists gave the name to the element by the color of the most characteristic red lines of its spectrum (from Latin rubidus - red). Rubidium metal was first obtained by R. Bunsen in 1863.
rubidium properties
Rubidium is a soft, silvery-white metal; the crystal lattice is cubic, body-centered: a = 0.57 nm. Density 1525 kg/m3; melting point 39.47°C; boiling point 685°C; thermal conductivity l 22.2 W / (m.K); heat capacity Ср0 31.09 J/(mol.K). Electrical resistivity 11.6.10 -6 Ohm.cm, temperature coefficient of linear expansion 90.10 -6 K -1.
+1 oxidation state. It ignites instantly in air, rubidium combines violently with oxygen, giving rubidium peroxide (Rb 2 O 2) and rubidium superoxide (RbO 2). Rubidium reacts explosively with water, hydrogen is released and a solution of rubidium hydroxide (RbOH) is formed, which is similar in properties to alkali metal hydroxides. Rubidium reacts with all inorganic acids. Almost all rubidium compounds are highly soluble in water.
rubidium in nature
Rubidium in a dispersed state is quite widespread in nature, however, despite the relatively high content in the earth's crust (1.5 .10 -2%, i.e. more than copper, zinc and other elements), rubidium does not form its own minerals . As an isomorphic impurity, rubidium is included in the minerals of other alkali metals and, above all, potassium. Compared to potassium, rubidium is concentrated in minerals of later stages of differentiation. Minerals rich in rubidium include concentrator minerals: pollucite, lepidolite, zinnwaldite, amazonite, biotite. The average content of rubidium in rocks increases in the order from basic to acid from 0.1.10 -4 to 1.7.10 -4 g/t. A relatively high concentration of rubidium is observed in the minerals of low-temperature pegmatite veins (up to 1-3% rubidium). The main industrial reserves of rubidium are concentrated in
In 1861, the recently invented physical method for studying substances - spectral analysis - once again demonstrated its power and reliability, as a guarantee of a great future in science and technology. With its help, the second previously unknown chemical element, rubidium, was discovered. Then, with the discovery of the periodic law by D. I. Mendeleev in 1869, rubidium, along with other elements, took its place in the table, which brought order to chemical science.
Further study of rubidium showed that this element has a number of interesting and valuable properties. We will consider here the most characteristic and important of them.
General characteristics of a chemical element
Rubidium has an atomic number of 37, that is, in its atoms, the composition of the nuclei includes just such a number of positively charged particles - protons. Accordingly, a neutral atom has 37 electrons.
The element symbol is Rb. Rubidium is classified as an element of group I, the period is fifth (in the short-period version of the table, it belongs to the main subgroup of group I and is located in the sixth row). It is an alkali metal, is a soft, very low-melting, silver-white crystalline substance.
Discovery history
The honor of discovering the chemical element rubidium belongs to two German scientists - chemist Robert Bunsen and physicist Gustav Kirchhoff, the authors of the spectroscopic method for studying the composition of matter. After the use of spectral analysis led to the discovery of cesium in 1860, the scientists continued their research, and the very next year, when studying the spectrum of the mineral lepidolite, they discovered two unidentified dark red lines. It is thanks to the characteristic shade of the strongest spectral lines, by which it was possible to establish the existence of a previously unknown element, that it got its name: the word rubidus is translated from Latin as “crimson, dark red”.
In 1863, Bunsen was the first to isolate metallic rubidium from mineral spring water by evaporating a large amount of solution, separating potassium, cesium and rubidium salts, and finally reducing the metal using soot. Later, N. Beketov managed to recover rubidium from its hydroxide using aluminum powder.
Physical characteristic of the element
Rubidium is a light metal, it has a density of 1.53 g/cm 3 (at zero temperature). Forms crystals with a cubic body-centered lattice. Rubidium melts at only 39 °C, that is, at room temperature, its consistency is already close to pasty. The metal boils at 687 ° C, its vapors have a greenish-blue tint.
Rubidium is a paramagnet. In terms of conductivity, it is more than 8 times superior to mercury at 0 ° C and is almost as many times inferior to silver. Like other alkali metals, rubidium has a very low photoelectric effect threshold. To excite a photocurrent in it, long-wavelength (that is, low-frequency and carrying less energy) red light rays are sufficient. In this respect, only cesium surpasses it in sensitivity.
isotopes
Rubidium has an atomic weight of 85.468. It occurs in nature in the form of two isotopes that differ in the number of neutrons in the nucleus: rubidium-85 makes up the largest proportion (72.2%), and in a much smaller amount - 27.8% - rubidium-87. The nuclei of their atoms, in addition to 37 protons, contain 48 and 50 neutrons, respectively. The lighter isotope is stable, while rubidium-87 has a huge half-life of 49 billion years.
At present, several dozens of radioactive isotopes of this chemical element have been artificially obtained: from ultralight rubidium-71 to rubidium-102 overloaded with neutrons. The half-lives of artificial isotopes vary from a few months to 30 nanoseconds.
Basic chemical properties
As noted above, in a number of chemical elements, rubidium (like sodium, potassium, lithium, cesium and francium) belongs to alkali metals. The peculiarity of the electronic configuration of their atoms, which determines the chemical properties, is the presence of only one electron at the external energy level. This electron easily leaves the atom, and the metal ion at the same time acquires an energetically favorable electronic configuration of the inert element in front of it in the periodic table. For rubidium, this is the krypton configuration.
Thus, rubidium, like other alkali metals, has pronounced reducing properties and an oxidation state of +1. Alkaline properties are more pronounced with an increase in atomic weight, since the radius of the atom also increases, and, accordingly, the bond between the outer electron and the nucleus is weakened, which leads to an increase in chemical activity. Therefore, rubidium is more active than lithium, sodium and potassium, and cesium, in turn, is more active than rubidium.
Summarizing all of the above about rubidium, the analysis of the element can be done, as in the illustration below.
Compounds formed by rubidium
In air, this metal, due to its exceptional reactivity, oxidizes violently, with ignition (the flame has a violet-pinkish color); during the reaction, superoxide and rubidium peroxide are formed, which exhibit the properties of strong oxidizing agents:
- Rb + O 2 → RbO 2.
- 2Rb + O 2 → Rb 2 O 2 .
An oxide is formed if the access of oxygen to the reaction is limited:
- 4Rb + O 2 → 2Rb 2 O.
It is a yellow substance that reacts with water, acids and acid oxides. In the first case, one of the strongest alkalis is formed - rubidium hydroxide, in the rest - salts, for example, rubidium sulfate Rb 2 SO 4, most of which are soluble.
Even more violently, accompanied by an explosion (since both rubidium and the released hydrogen instantly ignite), the metal reacts with water, in which rubidium hydroxide, an extremely aggressive compound, is formed:
- 2Rb + 2H 2 O → 2RbOH + H 2 .
Rubidium is a chemical element that can also directly react with many non-metals - with phosphorus, hydrogen, carbon, silicon, and halogens. Rubidium halides - RbF, RbCl, RbBr, RbI - are highly soluble in water and in some organic solvents, such as ethanol or formic acid. The interaction of metal with sulfur (rubbing with sulfur powder) occurs explosively and leads to the formation of sulfide.
There are also poorly soluble compounds of rubidium, such as RbClO 4 perchlorate, they are used in analytics to determine this chemical element.
Being in nature
Rubidium is an element that is not rare. It is found almost everywhere, is part of many minerals and rocks, and is also found in the ocean, in underground and river waters. In the earth's crust, the content of rubidium reaches the total value of the content of copper, zinc and nickel. However, unlike many much rarer metals, rubidium is an extremely trace element, its concentration in the rock is very low, and it does not form its own minerals.
In the composition of minerals, rubidium accompanies potassium everywhere. The highest concentration of rubidium is found in lepidolites, minerals that also serve as a source of lithium and cesium. So rubidium is always present in small amounts where other alkali metals are found.
A little about the use of rubidium
Brief description of the chem. rubidium element can be supplemented with a few words about the areas in which this metal and its compounds are used.
Rubidium is used in the production of photovoltaic cells, in laser technology, and is part of some special alloys for rocket technology. In the chemical industry, rubidium salts are used due to their high catalytic activity. One of the artificial isotopes, rubidium-86, is used in gamma-ray flaw detection and, in addition, in the pharmaceutical industry for the sterilization of drugs.
Another isotope, rubidium-87, is used in geochronology, where it serves to determine the age of the oldest rocks due to its very long half-life (rubidium-strontium method).
If several decades ago it was believed that rubidium is a chemical element, the scope of which is unlikely to expand, then at present new prospects for this metal appear, for example, in catalysis, in high-temperature turbine units, in special optics and in other areas. So in modern technologies, rubidium plays and will continue to play an important role.
At first glance, rubidium does not make much of an impression. True, it is shown not on black velvet, but in a sealed and pre-evacuated glass ampoule. With its shiny, silvery-white surface, this alkali metal resembles most other metals in appearance. However, a closer acquaintance reveals a number of unusual, sometimes unique features inherent in it.
So, it takes only a few minutes to hold an ampoule with rubidium in your hands, as it turns into a semi-liquid mass - after all, the melting point of rubidium is only 39 ° C.
The atomic mass of rubidium is average between the atomic masses of copper and silver, but its properties are sharply different from the properties of the "neighbor" metals. However, this was to be expected, given the location of rubidium in the periodic table. First of all, it is light (density 1.5 g / cm 3) and poorly conducts electric current. But the most remarkable thing is its exceptional chemical activity. Rubidium is stored in a vacuum for good reason - it instantly ignites in air. In this case, compounds with a high oxygen content are formed - rubidium peroxides and superoxides. No less greedily (with ignition) it combines with chlorine and other halogens, and with sulfur and phosphorus - even with an explosion.
In general, rubidium reacts with almost all elements; the literature describes its compounds with hydrogen and nitrogen (hydrides and nitrides), with boron and silicon (borides and silicides), with gold, cadmium and mercury (aurids, cadmides, mercurides), and many others.
At ordinary temperatures, rubidium decomposes water so violently that the liberated hydrogen immediately ignites. At 300°C, its vapors destroy glass, displacing silicon from it.
It is known that many metals have photoelectric properties. Light falling on cathodes made of these metals excites an electric current in the circuit. But if in the case of platinum, for example, this requires rays with a very short wavelength, then in rubidium, on the contrary, the photoelectric effect occurs under the action of the longest wavelengths of the visible spectrum - red. This means that less energy is required to excite a current in a rubidium photocell. In this regard, rubidium is second only to cesium, which is sensitive not only to light, but also to invisible infrared rays.
The exceptionally high activity of rubidium is also manifested in the fact that one of its isotopes - 87 Rb (and it accounts for 27.85% of the natural reserves of rubidium) - is radioactive: it spontaneously emits electrons (beta rays) and turns into an isotope of strontium with a period half-life of 50-60 billion years.
About 1% of strontium was formed on Earth in this way, and if we determine the ratio of isotopes of strontium and rubidium with an atomic mass of 87 in any rock, then we can calculate its age with great accuracy.
This method is suitable for the most ancient rocks and minerals. With its help, it was established, for example, that the oldest rocks of the American continent arose 2100 million years ago.
As you can see, this outwardly unpretentious silvery-white metal has many interesting properties.
Why is it called rubidium? Rubidus is Latin for red. It would seem that this name is more suitable for copper than for rubidium, which is very common in color. But let's not jump to conclusions.
This name was given to element #37 by its discoverers Kirchhoff and Bunsen. More than a hundred years ago, while studying various minerals with a spectroscope, they noticed that one of the samples of lepidolite sent from Rosen (Saxony) gives special lines in the dark red region of the spectrum. These lines were not found in the spectra of any known substance. Soon, similar dark red lines were found in the spectrum of sediment obtained after the evaporation of healing waters from the mineral springs of the Black Forest. It was natural to assume that these lines belong to some new, hitherto unknown element. So in 1861 rubidium was discovered. But its content in the tested samples was negligible, and in order to extract more or less tangible amounts, Bunsen had to evaporate over 40 m 3 of mineral water. From the stripped off solution, he precipitated a mixture of potassium, rubidium and cesium chloroplatinates. To separate rubidium from its closest relatives (and especially from a large excess of potassium), the scientist subjected the precipitate to multiple fractional crystallization and obtained rubidium and cesium chlorides from the least soluble fraction. Bunsen then converted them into carbonates and tartrates (salts of tartaric acid), which made it possible to further purify rubidium and free it from the bulk of cesium. Huge work and outstanding ingenuity bore fruit: Bunsen managed to resolve a very difficult issue and obtain not only individual salts of rubidium, but also the element itself.
Rubidium metal was first obtained by reducing acid tartrate with carbon black. At present, the best way to extract rubidium is to reduce its chloride with calcium metal. The reaction is carried out in an iron test tube placed in a tubular quartz device. In a vacuum at 700...800°C, rubidium gives up its chlorine to calcium, and sublimates itself. Its vapors are collected in a special branch of the device; there they are cooled, after which the entire process with the rubidium contained in it is soldered off. High purity rubidium metal can be obtained after repeated distillation under vacuum at 365°C.
How much rubidium is on the globe and where is it found? The last question is easier to answer: almost everywhere; but the answers to the first one are rather contradictory. Different researchers give different numbers. It is now generally accepted that the content of rubidium in the earth's crust is 1.5·10–2%. This is more than that of such well-known metals as copper, zinc, tin, lead. But it is much more difficult to isolate rubidium than tin or lead, and the point is not only in the high chemical activity of element No. 37. The trouble is that rubidium does not form clusters, it does not have its own minerals. It is extremely dispersed and occurs together with other alkali metals, always accompanying potassium.
Rubidium is found in many rocks and minerals, but its concentration there is extremely low. Only lepidolites contain slightly more Rb 2 O, sometimes 0.2%, and occasionally up to 1...3%. Rubidium salts are dissolved in the water of the seas, oceans and lakes. Their concentration here is also very low, on average about 100 µg/L. This means that there is hundreds of times less rubidium in the world ocean than in the earth's crust. However, in some cases, the content of rubidium in water is higher: in the Odessa estuaries it turned out to be 670 μg/l, and in the Caspian Sea - 5700 μg/l. An increased content of rubidium was also found in some mineral springs in Brazil.
Rubidium is found in seaweed, in tea, coffee, sugar cane and tobacco: up to 0.004% rubidium was found in the ashes of tobacco leaves (and they contain 1000 times more potassium).
From sea water, rubidium passed into potash salt deposits, mainly into carnallites. In Strassfurt and Solikamsk carnallites, the content of rubidium ranges from 0.037 to 0.15%. The mineral carnallite is a complex chemical compound formed by potassium and magnesium chlorides with water; its formula is KCl MgCl 2 6H 2 O. Rubidium gives a salt of a similar composition RbCl MgCl 2 6H 2 O, and both salts - potassium and rubidium - have the same structure and form a continuous series of solid solutions, crystallizing together. Carnallite is highly soluble in water, so the "opening" of the mineral is not difficult. Quite rational and economical methods for extracting rubidium from carnallite along with other elements have now been developed and described in the literature.
Powerful deposits of carnallite are undoubtedly one of the most promising sources of rubidium raw materials. Although the concentration of rubidium here is low, the total salt reserves are such that the amount of rubidium is measured in millions of tons.
Where is rubidium used? Where does it go and what benefits does it bring? Alas, reader! The track record of rubidium is small. World production of this metal is negligible (several tens of kilograms per year), and the cost is exorbitantly high: 2.5 dollars per 1 g. This is mainly explained by the insignificant reserves of rubidium in the main capitalist countries. And yet you cannot call it a completely “unemployed” element.
Rubidium preparations are sometimes used in medicine as sleeping pills and painkillers, as well as in the treatment of certain forms of epilepsy. Some of its compounds are used in analytical chemistry as specific reagents for manganese, zirconium, gold, palladium and silver. The metal itself is occasionally used for the manufacture of photocells, but rubidium photocathodes are inferior in sensitivity and range of action to some others, in particular cesium ones.
Meanwhile, studies carried out by scientists from various countries have shown that rubidium and its compounds have many practically valuable qualities. Among them, catalytic activity is of paramount importance.
Back in 1921, German chemists Fischer and Tropsch found that rubidium carbonate is an excellent catalyst component for producing synthetic oil - synthol. Synthol was called a mixture of alcohols, aldehydes and ketones, formed from water gas (a mixture of hydrogen with carbon monoxide) at 410 ° C and a pressure of 140 ... 150 atm in the presence of a special catalyst. After adding benzene, this mixture could be used as motor fuel. The catalyst was iron shavings impregnated with potassium hydroxide. But if potassium is replaced by rubidium, then the efficiency of the process increases significantly. First, the yield of oily products and higher alcohols doubles; secondly, the rubidium catalyst (unlike the potassium one) is not covered with soot and therefore retains its original activity much longer.
Later, special catalysts with rubidium were patented for the synthesis of methanol and higher alcohols, as well as styrene and butadiene. The starting products were: in the first case - water gas, in the second - ethylbenzene and butylene fraction of oil.
Styrene and butadiene are the starting materials for the production of synthetic rubber, and therefore their production occupies a prominent place in the chemical industry of highly developed countries. Usually the catalysts here are iron oxides with an admixture of oxides of other metals, mainly copper, zinc, chromium, manganese or magnesium, impregnated with potassium salts.
But if, instead of potassium, up to 5% rubidium carbonate is introduced into the catalyst, the reaction rate doubles. In addition, the so-called selective action of the catalyst and its stability are significantly increased, i. the process goes in the desired direction, without the formation of by-products, and the catalyst lasts longer and does not require frequent replacement.
In recent years, catalysts containing rubidium in one form or another have been proposed for hydrogenation, dehydrogenation, polymerization, and some other reactions of organic synthesis. For example, metallic rubidium facilitates the process of obtaining cyclohexane from benzene. In this case, the process proceeds at much lower temperatures and pressures than when it is activated with sodium or potassium, and it is almost not interfered with by poisons that are “lethal” for conventional catalysts - substances containing sulfur.
Rubidium carbonate has a positive effect on the polymerization of amino acids; with its help, synthetic polypeptides with a molecular weight of up to 40,000 were obtained, and the reaction proceeds without inertia, instantly.
A very interesting study was carried out in the USA in connection with the work on finding new types of aviation fuel. It was found that rubidium tartrate can be a catalyst in the oxidation of soot with nitrogen oxides, significantly lowering the temperature of this reaction compared to potassium salts.
According to some reports, rubidium accelerates the isotope exchange of a number of elements. In particular, its ability to combine directly with both hydrogen and deuterium can be used to produce heavy hydrogen, since rubidium deuteride is more volatile than ordinary hydride. It is possible that rubidium hydride, and especially rubidium borohydrides, can be used as high-calorie additives to solid fuels.
It is known that compounds of rubidium with antimony, bismuth, tellurium, suitable for the manufacture of photocathodes, have semiconductor properties, and its monosubstituted phosphates and arsenates can be obtained in the form of piezoelectric crystals.
Finally, in eutectic * mixtures of rubidium chlorides with chlorides of copper, silver or lithium, the electrical resistance decreases with increasing temperature so sharply that they can become very convenient thermistors in various electrical installations operating at a temperature of 150 ... 290 ° C.
* Eutectic is the most fusible composition of two (or more) substances, taken in a certain ratio.
This is by no means a complete list of the possibilities that rubidium has ...
In the Northern Urals, among dense forests, there is the ancient Russian city of Solikamsk. During the years of Soviet power, on the high bank of the Kama, near the old Solikamsk, a new city, shining with lights, grew up. One of the first mines of the Solikamsk potash plant is located here. Going down this shaft, you find yourself on a fairly wide area, somewhat reminiscent of a metro station. It is just as light and cozy here, and the walls are “lined” with sylvinite, shining like marble, with potassium-sodium mineral sylvinite. Silvinite is colored in different colors: sometimes it is snow-white (the purest sylvin is potassium chloride), sometimes it shimmers with all shades from light pink to almost red and from light blue to dark blue. It is permeated with transparent and colorless crystals of sodium chloride. But among them sometimes come across large shiny and completely black cubes.
Where did black salt come from?
It is believed that this is the handwriting of rubidium, that sodium chloride turned black under the influence of radioactive radiation of 87 Rb. So rubidium reminds of itself, lets you know about its existence.
Not only spectrographers
The discoverers of rubidium and cesium, the German scientists R. Bunsen and G. Kirchhoff, became famous not only as the creators of spectral analysis. Each of them owns a lot of interesting works and discoveries.
Kirchhoff
Gustav Robert Kirchhoff is a world-famous physicist. He established the laws of the flow of electric current in branched circuits, introduced the concept of an absolutely black body into physics, and formulated the basic law of thermal radiation.
In 1861, Kirchhoff established that the Sun consists of an incandescent liquid mass surrounded by an atmosphere of vapors, and made correct assumptions about the chemical composition of these vapors. Throughout his life, Kirchhoff was a convinced materialist. Spectral analysis, the foundations of which were laid by Kirchhoff and Bunsen, has become the most important physical and chemical method of scientific research. It is widely used in our time.
Bunsen
Robert Wilhelm Bunsen is an outstanding German chemist of the 19th century. Buizen's first major work was the study of organic compounds of arsenic. In 1841, he invented a carbon-zinc galvanic cell, the electromotive force of which reached 1.7 V. At that time it was the most powerful galvanic cell. Using a battery of such elements, Bunsen received magnesium, calcium, lithium, strontium, and barium from molten salts by electrolysis.
The scientist paid much attention to the determination of the physical constants of the most important substances. He developed precise methods of gas analysis, invented and improved many laboratory instruments and equipment. Disposable burners and Bunsen flasks for filtering are still used in laboratories around the world.
Bunsen was selflessly devoted to science. Working with arsenic, he was seriously poisoned, during one of the explosions in the laboratory he lost an eye.
The merits of the scientist were recognized by the whole world. In 1862, the Russian Academy of Sciences elected him a foreign corresponding member.
Rubidium(lat. Rubidium), Rb, a chemical element of Group I of Mendeleev's Periodic Table; atomic number 37, atomic mass 85.4678; silvery-white metal, belongs to the alkali metals. Natural Rubidium is a mixture of two isotopes: stable 85 Rb (72.15%) and weakly radioactive 87 Rb (half-life T ½ 4.8 10 10 years). The β-decay of 87 Rb produces stable 87 Sr. Determination of the content of 87 Sr and Rubidium in rocks and minerals (strontium method) makes it possible to reliably determine their geological age. About 20 radioactive isotopes of Rubidium have been artificially obtained. Rubidium was discovered in 1861 by R. Bunsen and G. Kirchhoff during a spectral study of salts isolated from mineral waters. The name of the element is given by the color of the most characteristic red lines of the spectrum (from Latin rubidus - red, dark red). Metal Rubidium was obtained for the first time in 1863 by Bunsen.
Distribution of Rubidium in nature. Rubidium is a typical trace element. Despite the relatively high content in the earth's crust (clarke) of 1.5 10 -2% by weight, that is, more than that of Cu, Pb, Zn and many other metals, Rubidium does not form its own minerals and is mainly included as an isomorphic impurity in potassium and cesium minerals (sylvin, carnallite, microcline, Rb-muscovite, etc.). Rubidium, like potassium, is found in acidic igneous rocks (granitoids) and especially in pegmatites (up to 1-3% Rubidium). There is little Rubidium in ultrabasic and basic rocks (2·10 -4 and 4.5·10 -3%, respectively). The waters of the seas and oceans contain from 1.0·10 -5 to 2.1·10 -5% Rubidium. Rubidium salts are part of the waters of many mineral springs.
The most rich in Rubidium are the so-called concentrating minerals: lepidolite, zinnwaldite, pollucite. There are deposits of lithium and potassium minerals containing Rubidium in the USSR, Czechoslovakia, Germany, Namibia, Zimbabwe and other countries. The cosmic abundance of Rubidium is 6.5 atoms per 10 6 silicon atoms.
Physical properties of Rubidium. Rubidium forms silvery-white soft crystals that have a metallic luster on a fresh cut. Brinell hardness 0.2 MN / m 2 (0.02 kgf / mm 2). The crystal lattice of Rubidium is cubic, body-centered, a = 5.70Å (0 °C). Atomic radius 2.48 Å, ion radius Rb + 1.49 Å. Density 1.525 g / cm 3 (0 ° С), t pl 38.9 ° С, t bp 703 ° С. Specific heat 335.2 j / (kg K), thermal coefficient of linear expansion 9.0 10 -5 deg -1 (0-38 ° C), modulus of elasticity 2.4 Gn / m 2 (240 kgf / mm 2 ), specific volume electrical resistance 11.29 10 -6 ohm cm (20 °C); Rubidium is paramagnetic.
Chemical properties of Rubidium. The Rb atom easily donates the only electron of the outer shell (its configuration is 5s 1). Electronegativity Rubidium 0.89, first ionization potential 4.176 eV. In all chemical compounds, Rubidium is monovalent (oxidation state +1). The chemical activity of Rubidium is very high. It combines with oxygen violently, giving peroxide Rb 2 O 2 and superoxide RbO 2 (with a lack of oxygen, oxide Rb 2 O is formed). Rubidium reacts explosively with water, releasing hydrogen and forming a solution of rubidium hydroxide, RbOH. The properties of RbOH strongly resemble potassium hydroxide KOH. Rubidium combines directly with many non-metals; reacts violently with most acids. Almost all Rubidium salts are highly soluble in water. Slightly soluble perchlorate RbClO 4 , chloroplatinate Rb 2 and some others; they are used for the analytical determination of Rb along with the flame photometry method based on the property of Rb vapor and its compounds to color the flame bright red.
Obtaining Rubidium. Rb salts are obtained as a by-product in the production of Li, Mg and K salts. Rubidium metal is obtained by reduction of RbCl in vacuum at 700-800 °C with calcium. Due to its high reactivity, Rubidium is stored in metal vessels under a layer of paraffin oil or in sealed glass ampoules in an inert atmosphere.
Application of Rubidium. Rubidium is used mainly in the production of cathodes for photocells; also added to gas-discharge argon and neon tubes to enhance the intensity of the glow. Sometimes Rubidium is introduced into special alloys (getters). Rubidium salts are used as catalysts in organic synthesis.
Rubidium in the body. Rubidium is constantly present in the tissues of plants and animals. Terrestrial plants contain about 0.00064% Rubidium, while aquatic plants contain 2 times less. Rubidium accumulates in plants, as well as in the muscles and soft tissues of sea anemones, worms, mollusks, crustaceans, echinoderms and fish (accumulation factor 8-26). The highest accumulation coefficient (2600) of the artificial radioactive isotope 86 Rb is in the duckweed Lemna polyrrhiza, and among freshwater invertebrates in the mollusk Galba palustris - 370. The ashes of the pectoral muscles of birds contain 0.0112-0.0135%. Rubidium metabolism in the body is poorly studied.
rubidium element is a white alkali metal with a metallic luster (see photo). Easy to melt, this process takes place at a temperature of only 39°C. In all its characteristics, the element is similar to potassium and sodium. The name Rubidium is lat. dark red was not assigned to him for his natural color. German scientists Bunsen and Kirchhoff examined a new substance in a spectrograph, and noticed red lines.
Rubidium is a very active element, but its characteristic feature is that most of the reactions take place with an explosion, and combustion is accompanied by a bright violet flame. In a similar way, interaction with all known elements occurs, regardless of their nature (metal-non-metal). Store it in vessels with dry kerosene or in a vacuum. In addition to being active, rubidium is also a radioactive element that gradually turns into strontium.
This substance, by its very nature, is very unique. Under the influence of light, it becomes a source of electric current. This phenomenon is called the photoelectric effect, and allows the element to be used for the manufacture of photocells used in cinema, television, and remote control of automation. Rubidium is valued very highly, and therefore the use is quite small (several tens of kilograms per year).
It is also used in the manufacture of measuring instruments, as components of lubricants for rocket and space technology operating in vacuum, in X-ray equipment. It is thanks to the content of rubidium and strontium in the rocks that geologists are able to determine their age.
In nature, rubidium is quite common, but only in the form of impurities. Its salts are often found in mineral springs and in volcanic rocks.
The action of rubidium and its biological role
The effect of a macroelement on a biological organism is associated with its concentration in certain organs: bone tissue, lungs, brain, ovaries. Its absorption from food occurs in the gastrointestinal tract, and it is excreted with natural secretions.
Scientists have not yet sufficiently studied the effect of the element on humans, but without a doubt, it plays a significant role in the body and has such an effect:
- can to some extent replace potassium and play its role in the activation of enzymes;
- has an antihistamine effect (combats exposure to allergens);
- weakens inflammatory processes in cells and the body as a whole;
- restores the balance of the central nervous system, has a calming effect.
Today, scientists are studying the effect of the element on the stimulation of blood circulation and the use of these properties to treat hypotension. Another well-known doctor S. Botkin in 1898 noticed that rubidium chloride is able to increase pressure in the arteries and associated this with the process of vasoconstriction and activation of the cardiovascular system.
It has also been observed that microdoses of the element can cause the resistance of erythrocytes to harmful effects, and increase the mass of hemoglobin in them. This in turn leads to increased immunity.
Most often, the study of rubidium is carried out in combination with cesium. Salts of these elements help to endure hypoxia - lack of oxygen.
We hope that this element will reveal many more of its unique abilities to the medical and scientific world.
Daily rate
The daily norm of a macronutrient for an adult is approximately 1-2 mg. It is quickly absorbed by the body - after 1-1.5 hours you can find its content in the blood. In total, human tissues and organs contain about 1 gram of rubidium.
Deficiency of a chemical element in the body
The lack of a macronutrient and its effect on the human body is practically not studied. The experiments were carried out only on animals and their reaction was as follows:
- loss of appetite, and even a complete refusal to eat;
- growth retardation, slow development, shortened life span;
- premature birth, miscarriages;
- deviations in the development of the fetus and a decrease in fertility.
Excess rubidium
An excess of a macronutrient can cause dangerous complications for the reason that rubidium belongs to the same category of poisonous and toxic elements as arsenic and sulfuric acid. Overdose can cause serious harm to health and even death.
The reason for such large doses can be work in enterprises where compounds of a substance are used that penetrate the body with vapors and dust. Theoretically, one of the reasons could be excessive consumption of the element from food and water.
A slight increase in the level of a macronutrient can lead to migraines, insomnia, diseases and inflammations of the lungs and respiratory organs, rapid heartbeat (arrhythmias), skin allergic diseases and increased levels of proteins in the urine. If the poisoning is caused by the accumulation of critical masses of the element, then the consequences are similar to those caused by the deficiency of the element: slowdown in growth and development, shortening of life.
Another uniqueness? The good news is that you need to take more than 1000mg daily for these symptoms to appear, which is already very difficult.
Treatment of poisoning is carried out with substances that, when reacting with toxins, form compounds that dissolve easily in water and are excreted by the kidneys. Basically it is a complexing agent based on potassium or sodium. Also, drugs are used that are ways to relieve characteristic symptoms.
What are the sources of the element?
The list of foods containing rubidium mainly consists of plant foods. Here are the most basic of them: eggplant, ginger, potatoes, beets, tomatoes, garlic, onions, mushrooms (champignons and porcini mushrooms), many fruits and dried fruits, nuts (almonds, walnuts and cedar, hazelnuts, pistachios), sunflower seeds, cereals , legumes. Our body receives the largest amount with tea and coffee (about 40% of the total amount) and mineral water, depending on the origin.
This element is able to accumulate in living tissues, especially in marine organisms. Therefore, the use of seafood will help to get the required amount of rubidium.
Indications for appointment
Indications for the appointment of a macroelement come from the nature of the impact on the human body. Its main medicinal purpose is the treatment of disorders of the nervous system. Even 100 years ago, it was actively used to get rid of epilepsy. Today it is used as a neurotropic drug to strengthen the nervous system.
It may also be necessary in the treatment of allergic diseases, muscle weakness, anemia.
