Platinum designation in the periodic table. Ruthenium: the cost of a gram of metal and its scope. Obtaining pure metal

Platinum, Platinum, Pt (78)

Platinum (English Platinum, French Platine, German Platin) was probably known in antiquity. The first description of platinum as a highly fire-resistant metal, which can only be melted with the help of "Spanish art", was made by the Italian physician Scalinger in 1557. Apparently, at the same time the metal received its name "platinum". It displays a dismissive attitude towards metal, as there is little to anything suitable and not amenable to processing. The word "platinum" comes from the Spanish name for silver - board (Plata) and is a diminutive form of this word, which in Russian sounds like silver, silver (according to Mendeleev - silver). It is interesting to note that the word platinum is consonant with the Russian "fee" (pay, payment, etc.) and is close to it in meaning. In the 17th century platinum was called Platina del Pinto, because it was mined in the golden sand of the Pinto River in South America; there was another name of this kind - Platina del Tinto from the Rio del Tinto river in Andalusia. Platinum was described in more detail in 1748 by de Walloa, a Spanish mathematician, navigator and merchant. Starting from the second half of the XVIII century. Many analytical chemists and technologists, including scientists from the St. Petersburg Academy of Sciences, became interested in platinum, its properties, methods of processing and use. The most important work in this area in the first half of the 19th century was the creation of methods for obtaining malleable platinum (Sobolevsky, Wollaston, and others), the discovery of some of its compounds (Musin-Pushkin, and others) and platinum group metals.

PLATINUM (lat. Platinum)

General information

Chemical element of the periodic table, metal.
Element symbol: Pt.
atomic number: 78.
Position in the table: 6th period, group - VIIIB(10).
Relative atomic mass: 195,083.
Oxidation states: +2, +3, +4, +6 and rarely +5.
valency: II, III, IV, V, VI.
Electronegativity: 2,2.
Electronic configuration: 5s 2 p 6 d9 6 s 1 .
Platinum consists of four stable isotopes 194 Pt (32.9%), 195 Pt (33.8%), 196 Pt (25.2%), 198 Pt (7.2%) and two weakly radioactive 190 Pt (0.013% , half life T 1/2= 6.9 10 11 years), 192 Pt (0.78%, T 1/2= 10 15 years).

The structure of the atom

Number of electrons: 78.
Atom radius 0.138 nm, ionic ion radius Pt 2+ - 0.074 (coordination number 4), Pt 2+ - 0.094 (6), Pt 4+ - 0.0765 (6), Pt 5+ - 0.071 nm (6). The ionization energies of Pt 0 - Pt + - Pt 2+ - Pt 3+ are equal to 9.0, 18.56, 23.6 eV.

Discovery history

Platinum has been known to mankind since ancient times. Products containing platinum have been found during excavations of ancient Egyptian tombs and ancient Indian settlements in Colombia. The first description of platinum in Europe was made by A. de Ulloa, who participated in a French expedition in 1736 to determine the length of the equator. Noble metal is mentioned in his records platinum, found in Colombian gold mines.
In 1741, South American samples of the metal were brought to Europe, where at first platinum was considered as "white gold". In the middle of the 18th century, the elemental nature of platinum was established. Currently, "white gold" refers to alloys of gold and platinum. Pure platinum was melted down in 1783 by A. L. Lavoisier.

Receipt

The production of platinum in powder form began in 1805 by the Englishman W. H. Wollaston from South American ore.
Currently, platinum is obtained from a concentrate of platinum metals. The concentrate is dissolved in aqua regia, after which ethanol and sugar syrup are added to remove excess HNO 3 . In this case, iridium and palladium are reduced to Ir 3+ and Pd 2+ . Subsequent addition of ammonium chloride allocate (NH 4) 2 PtCl 6 . The dried precipitate is calcined at 800-1000°C:
(NH 4) 2 PtCl 6 \u003d N 2 + 6HCl + Pt + H 2.
The sponge platinum thus obtained is subjected to further purification by redissolving in aqua regia, precipitation of (NH 4 ) 2 PtCl 6 and calcining the residue. The purified spongy platinum is then melted down into ingots. When platinum solutions are reduced by a chemical or electrochemical method, finely dispersed platinum is obtained - platinum black.

Being in nature

Platinum is one of the rarest elements, its content in the earth's crust is 5·10 -7% by mass. It is found in nature in sulfide, copper-nickel and copper-molybdenum ores, in the form of nuggets and native alloys with iridium or palladium. Platinum minerals: PtAs 2 (sperrylite), PtS (couperite), (Pt, Pd, Ni) S (braggite).

Physical and chemical properties

Platinum - refractory heavy ( density at 20°C 21.45 g/cm 3) silver-white metal. It has a face-centered cubic lattice, a= 0.392 nm. Melting point 1769°C, boiling point 4170°C. Displays the properties of a paramagnet. Metal platinum lends itself well to rolling and welding. In a series of standard potentials, platinum is located to the right of hydrogen and does not react with non-oxidizing acids and water.
In terms of chemical properties, platinum is similar to palladium, but exhibits greater chemical resistance. Reacts only with hot aqua regia:
3Pt + 4HNO 3 + 18HCl = 3H 2 + 4NO + 8H 2 O
Platinum dissolves slowly in hot sulfuric acid and liquid bromine. It does not interact with other mineral and organic acids. When heated, it reacts with alkalis and sodium peroxide, halogens (especially in the presence of alkali metal halides):
Pt + 2Cl 2 + 2NaCl \u003d Na 2.
When heated, platinum reacts with sulfur, selenium, tellurium, carbon and silicon. Like palladium, platinum can dissolve molecular hydrogen, but the volume of absorbed hydrogen is smaller and the ability to give it away when heated is less for platinum.
When heated, platinum reacts with oxygen to form volatile oxides. The following platinum oxides have been isolated: black PtO, brown PtO 2 , reddish brown PtO 3 , as well as Pt 2 O 3 and Pt 3 O 4 .
For platinum, the hydroxides Pt(OH) 2 and Pt(OH) 4 are known. They are obtained by alkaline hydrolysis of the corresponding chloroplatinates, for example:
Na 2 PtCl 4 + 2NaOH \u003d 4NaCl + Pt (OH) 2 (precipitate),
Na 2 PtCl 6 + 4NaOH \u003d 6NaCl + Pt (OH) 4 (precipitate).
These hydroxides exhibit amphoteric properties:
Pt (OH) 2 + 2NaOH \u003d Na 2,
Pt (OH) 2 + 4HCl \u003d H 2 + 2H 2 O,
Pt (OH) 4 + 6HCl \u003d H 2 + 4H 2 O,
Pt (OH) 4 + 2NaOH \u003d Na 2.
PtF 6 hexafluoride is one of the strongest oxidizing agents capable of oxidizing oxygen, xenon or NO molecules:
O 2 + PtF 6 \u003d O 2 + -.
From the interaction between Xe and PtF 6 discovered by N. Bartlett, leading to the formation of XePtF 6 , the chemistry of inert gases began. PtF 6 is obtained by fluorination of platinum at 1000 °C under pressure.
Fluorination of platinum at normal pressure and temperature of 350-400 °C gives Pt(IV) fluoride:
Pt + 2F 2 = PtF 4
Platinum fluorides are hygroscopic and decompose with water.
Platinum (IV) tetrachloride with water forms hydrates PtCl 4 nH 2 O, where n = 1, 4, 5 and 7. Dissolving PtCl 4 in hydrochloric acid produces chloroplatinic acids H and H 2 .
Such platinum halides as PtBr 4 , PtCl 2 , PtCl 2 ·2PtCl 3 , PtBr 2 and PtI 2 have been synthesized.
Platinum is characterized by the formation of complex compounds of the composition 2- and 2-. Studying platinum complexes, A. Werner formulated the theory of complex compounds and explained the nature of the occurrence of isomers in complex compounds.

Application

The main application of platinum, its alloys and compounds are in the automotive industry (30-65%), as a catalyst for afterburning car exhaust gases. 7-12% of platinum is used in the oil refining industry and organic synthesis (in the hydrogenation of hydrocarbons), 7-13% - in electrical engineering and electronics, 3-17% - in the glass and ceramic industry, 2-35% - for the manufacture of dentures and jewelry.

Physiological role

All platinum compounds are strong oxidizing agents. And they require careful handling.

author unknown

Platinum (Platinum, Pt) is a chemical element at number 78 in the periodic table.

The poverty of platinum ores, the absence of large deposits, and hence the very high cost of the metal, to a large extent limit the practical use of platinum. Platinum is very rarely found in the form of nuggets. The largest of them weighs 9.6 kg.

In appearance, platinum does not represent anything outstanding or conspicuous. It is a white with a gray matte sheen, malleable (approaching gold) with a significant density (21.5) and a high melting point (1774 ° C) metal. The exceptional chemical resistance of platinum at the highest temperatures allows it to be called the metal of the chemical laboratory. Despite the fact that platinum was known as early as the first half of the 18th century (described by R. Watson in 1750), and vague references to it date back to the 16th century, platinum first found practical use in technology only in 1809 in the manufacture of retorts for storing concentrated sulfuric acid. The first deposits of native platinum were discovered in America, where in the 17th century the Spanish conquerors led by F. Cortes, having ruined the Aztec state, found a new metal on the banks of the Platino del Pino River (in Colombia). The name of the metal - "platinum" comes from the Spanish word "plata" - silver and means "silver". In its native form, platinum, in addition to America (Brazil, Colombia), is located in the Union of South Africa. In our Urals, primary deposits of platinum were discovered in 1892 by A. A. Inostrantsev. Placer deposits were found earlier, in 1819, but the famous Alexander Humboldt, who visited platinum deposits in 1829, did not write a single word about its use in his report.

For some time, platinum was considered a "worthless" metal. The conquerors of South America brought a lot of platinum to Spain, and it was sold cheaper than silver. However, Spanish jewelers, having discovered that alloys of platinum with gold have a large specific gravity, decided to use it to make, from the point of view of that time, a fake gold coin. Upon learning of this, the Spanish government issued an order to destroy all platinum reserves, and a large amount of the metal was drowned in the sea.

The properties of platinum were first described by Professor of Kharkov University F. Giese. A detailed study of platinum and methods of obtaining it from natural "raw platinum" was carried out by a Russian chemist, vice-president of the Mining College in St. Petersburg, an honorary member of the Russian and many foreign Academies of Sciences Musin-Pushkin.

It should be noted that Russian scientists play a leading role in the study of platinum and other metals accompanying it.

The high chemical resistance of platinum has ensured its wide application for the manufacture of chemical glassware (crucibles, cups, tongs, nozzles for burners, electrodes for analysis) and equipment for the chemical industry.

Platinum mirrors are known, they are obtained by applying the thinnest layer of platinum on a glass surface. Platinum mirrors are stable, do not fade, give a clear image, and most importantly, they have a remarkable feature - one-sided transparency. The essence of the phenomenon is that from the side of the light source the mirror is opaque and reflects the objects in front of it, while from the shadow side it is transparent and everything can be seen through the mirror as well as through clean glass. Thanks to this feature, platinum mirrors were widely used in the United States at one time. Instead of glass, they were inserted into the windows of the lower floors of offices, typewriting bureaus and other institutions, as well as living quarters, instead of curtains and screens.

Platinum also has one more valuable property: it is well soldered into glass, which is important in the manufacture of glass instruments.

The principle of operation of such resistance thermometers is based on the ability of platinum to change (increase) electrical resistance in strict dependence on temperature increase. If a platinum wire is connected to a device that registers a change in resistance, then the change in temperature will be accurately recorded by this device. The scale of the instrument is graduated in degrees.

Platinum is the favorite metal of jewelers. In jewelry art, platinum plays the role of a finishing material for gold.

A relief image of V. I. Lenin was made of platinum, placed in the middle of the badge of the Order of Lenin - the highest order of the USSR. The newspaper Komsomolskaya Pravda was awarded the first Order of Lenin.

Loose, spongy platinum absorbs a large amount of gases. This remarkable property explains the amazing fact: the gas enclosed in a platinum vessel, when heated, flows out of a hermetically sealed vessel. Just as water passes through a fine sieve, hydrogen or oxygen gas molecules pass through platinum partitions.

We have listed many interesting and valuable properties of platinum without touching on the most important: platinum is one of the most active catalysts for various chemical processes. One of the most important catalytic processes is the oxidation of ammonia to produce nitric acid. The thinnest mesh (up to 5000 holes per square centimeter), woven from platinum wires, similar to a thin fabric and as soft as light silk, is the main and most important part of the ammonia oxidation apparatus. A mixture of ammonia and air with the speed of a hurricane is blown through this grid, turning into nitrogen oxides and water vapor. When nitrogen oxides are dissolved in water, nitric acid is formed.

Pioneer of the domestic nitric acid industry Ivan Ivanovich Andreev, having carried out a large research work on studying the effect of various catalysts on the oxidation of ammonia, drew attention to platinum, introducing it into the practice of factory production of nitric acid.

The first world war was on. Shells, bombs and mines exploded on the battlefields, and factories for the production of metal, ammunition, and explosives were feverishly working in the deep rear. The production of explosives required more and more nitric acid, more than 2 kg of acid for every kg of explosives. By the end of 1916, the monthly need for explosives for the Russian army was 6400 tons. All the states participating in the war were in dire need of raw materials for the production of nitric acid. It was available only in South America (Chile), and in all countries there was a feverish search for raw materials for the manufacture of nitric acid. One of its types is ammonia contained in the waste of coke production. To convert ammonia into nitric acid, it must be oxidized. Knowing that ammonia is oxidized in the presence of platinum, I. I. Andreev designs a plant, which was soon built in the Donbass and commissioned in July 1917.

Various chemical compounds, which include platinum, do not yet have significant use. (Some are used in analytical chemistry for the quantitative determination of potassium). However, studies of these compounds have made a great contribution to the theory of chemistry. Platinum compounds have been most fully studied by Russian scientists L. A. Chugaev, I. I. Chernyaev, O. E. Zvyagintsev.

The existing idea that platinum does not interact with atmospheric oxygen, as studies have shown, is not true. So at room temperature, a very thin film (about 30 angstroms) is formed on platinum, which volatilizes with slight heating in a vacuum.

Ruthenium is a precious metal belonging to the platinum group of metals. The appearance of the metal directly depends on the method of its extraction, so it can be silvery white or matte gray. The name of the metal comes from Ruthenia, which means “Russia” in Latin, and this is no coincidence, since it was first found in the Urals. It is worth saying that ruthenium prices for 1 gram in rubles, which are quite low compared to other precious metals, are currently only 118 rubles.

Ruthenium is mined in South Africa, Russia, Canada and other countries. The main supplier of this noble metal today is South Africa. It is extracted from the remains of platinum production. It is present as an impurity in various metal ores.

Ruthenium is a rather diffuse chemical element, but there is only one mineral that is formed from it - this is laurite. It is also found in spent nuclear fuel products. A ton of radioactive waste contains about 250 g of ruthenium.

17-21 tons of ruthenium are mined per year all over the world. The total metal reserves on Earth, according to scientists, are only 5000 tons.

Properties

The main advantages of the metal are high hardness and increased resistance to various aggressive substances. In the periodic table, the element is on the 44th line. The hardness of the metal is 6.5 on the Mohs scale, according to this indicator it is ahead of platinum, at the same time it is very fragile.

At the same time, the metal is light, and its density is less than 13 g per cm3. It occupies the 8th place in terms of refractoriness. The melting point of the metal is 2334C, and the boiling point is about 4077C. In the process of heating it in the atmosphere, the element is partially oxidized. At a temperature of 1,000 C, ruthenium is oxidized to RuO2 dioxide, and at 1,200 C or more, to RuO4 tetroxide, which has the highest degree of valence 8+. The ability of ruthenium to quickly change valence makes scientists study it deeper.

RuO4 oxide is a yellow crystal that becomes a brown-orange liquid at 25°C, which smells very similar to ozone. Moreover, its contact with many organic substances leads to an explosion. RuO4 is a poisonous substance, therefore, if you breathe in its vapors for a long time, you will feel dizzy, vomiting and suffocation will appear. Some scientists working on RuO4 developed eczema.

The metal reacts at temperatures above 400C. In its normal state, the element does not dissolve even in aqua regia. He does not care for acids and alkalis.

In addition, this element has excellent gas absorption capacity. It absorbs hydrogen 1,500 times its volume, while it can absorb not only hydrogen, but also nitrogen, and in smaller quantities other non-metals.

Areas of use

jewelry industry

The metal has a bright luster and a pleasant bluish-gray tint, it does not oxidize, therefore it attracts the attention of jewelers. Very brittle, it is used as one of the alloying elements in precious alloys. This improves their hardness and wear resistance. However, it is difficult to work with it, as it has a high refractoriness.

Adding this element to a gold alloy gives it a black tone. Of course, they darken gold and rhodium, but the shade is not as saturated as with alloying ruthenium.

Medicine

In medicine, dyes with ruthenium compounds are used, which makes it possible to isolate tissues for their detailed study, including cancerous tumors. This helps surgeons to see all the affected cells and tissue areas.

This material is biologically active, so its compounds are used in the manufacture of drugs against cancer, tuberculosis and various infections that affect the skin.

electrical engineering

Due to its high refractoriness, this chemical element has found application in electrical engineering. Contacts and various elements of high-precision devices are made from it. Its high melting point has made it an indispensable material for thermocouples. Devices are needed to measure high temperatures.

When heated to 272.53 C, this material becomes a superconductor, which is in great demand in electrical engineering.

In electronics, they cover radio components for corrosion protection. This layer also makes them chemical resistant and protects against mechanical wear.

Space

This material is also in demand in the space industry - fuel cells for satellites are made from an alloy of platinum and ruthenium. This composition is able to withstand all overloads in Earth's orbit.

Chemistry

The chemical element ruthenium, due to the fact that it does not react with aggressive substances, is in great demand in chemistry. In addition, it has excellent catalytic abilities. Ruthenium catalysts make it possible to obtain glycerol and other alcohols from cellulose.

The main advantage of the ruthenium catalyst is its selectivity. Helps chemists to synthesize various organic as well as inorganic products. This catalyst competes with other platinum group metals.

glass industry

Ruthenium compounds are also used in the glass industry - they are also added to some enamels. There are also fluorescent coatings, the glow of which is caused by compounds of this material.

Other industries consume about 10% ruthenium.

Price

The current price of precious metals

The small amount of ruthenium on Earth and the difficulty of extracting this element make it very expensive. The price for one gram of metal constantly fluctuates, on average within 100-200 rubles.

Platinum (Spanish Platina) - element 78 of the periodic table, atomic mass 195.08; noble metal of gray-steel color.

Atomic number - 78
Atomic mass - 195.08
Density, kg/m³ - 21400
Melting point, ° С - 1769
Heat capacity, kJ / (kg ° С) - 0.134
Electronegativity - 2.2
Covalent radius, Å - 1.30
1st ionization potential, ev - 9.00 The history of platinum

The first deposits of native platinum were discovered in America, where in the 17th century the Spanish conquerors led by F. Cortes, having ruined the Aztec state, found a new metal on the banks of the Platino del Pino River (in Colombia). The name of the metal - "platinum" comes from the Spanish word "plata" - silver and means "silver". In its native form, platinum, in addition to America (Brazil, Colombia), is located in the Union of South Africa. In our Urals, primary deposits of platinum were discovered in 1892 by A. A. Inostrantsev. Alluvial deposits were found earlier, in 1819.

In the Old World, platinum was not known, but the Andean civilizations (Inca and Chibcha) mined and used it from time immemorial.

In Europe, platinum was unknown until the 18th century.

In 1735, the Spanish king issued a decree ordering platinum to no longer be imported into Spain. When developing placers in Colombia, it was ordered to carefully separate it from gold and drown under the supervision of royal officials in the deep places of the Rio del Pinto, which became known as Platino del Pinto. And the platinum that had already been brought to Spain was ordered publicly and solemnly to be drowned in the sea. The fact is that platinum is easily alloyed with gold and hardly differs from it in density, which counterfeiters did not fail to take advantage of.

In 1748, the Spanish mathematician and navigator A. de Ulloa was the first to bring samples of native platinum found in Peru to the European continent. For the first time, platinum was obtained in pure form from ores by the English chemist W. Wollaston in 1803. The Italian chemist Gilius Scaliger in 1835 discovered the indecomposability of platinum and thus proved that it is an independent chemical element.

In Russia, as early as 1819, “new Siberian metal” was discovered in alluvial gold mined in the Urals. At first it was called white gold, platinum was found on the Verkh-Isetsky, and then on the Nevyansk and Bilimbaevsky mines. Rich placers of platinum were discovered in the second half of 1824, and the following year, its mining began in Russia.