Story
Platinum was not known in the Old World until the mid-16th century, but the Andean civilizations (Inca and Chibcha) have mined and used it since time immemorial. The first Europeans to become acquainted with platinum in the middle of the 16th century were the conquistadors. It is believed that Scaliger was the first to mention platinum in literature in the book “Exoteric Exercises in 15 Books” published in 1557, where he, arguing with Cardano about the concept of “metal”, spoke about a certain substance from Honduras that cannot be melted. This substance was probably platinum.
In 1735, the Spanish king issued a decree ordering that platinum should no longer be imported into Spain. When developing placers in Colombia, it was ordered to carefully separate it from the gold and drown it under the supervision of royal officials in the deep places of the Rio del Pinto River (a tributary of the Rio San Juan (English) Russian), which became known as the Platino del Pinto. And the platinum that had already been brought to Spain was ordered to be publicly and solemnly drowned in the sea. The royal order was reversed 40 years later when the Madrid authorities ordered platinum to be delivered to Spain in order to counterfeit gold and silver coins themselves. In 1820, between 3 and 7 tons of platinum were delivered to Europe. Here alchemists met her, who considered gold to be the heaviest metal. The unusually dense platinum turned out to be heavier than gold, so alchemists considered it an unsuitable metal and endowed it with hellish traits. Platinum found some use later in France, when the meter standard was made from it, and later the kilogram standard.
According to some sources, the Spanish mathematician and navigator A. de Ulloa brought samples of platinum to London in 1744; he included a description of platinum in his report on a trip to South America, published in 1748. In 1789, A. Lavoisier included platinum in the list of simple substances. Platinum was first obtained in its pure form from ores by the English chemist W. Wollaston in 1803.
In Russia, back in 1819, a “new Siberian metal” was discovered in alluvial gold mined in the Urals, which was first called white gold. Platinum was found at the Verkh-Isetsky, and then at 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. In 1826, P. G. Sobolevsky and V. V. Lyubarsky invented a method for producing malleable platinum using pressing and subsequent exposure to a white-hot state.
Jewelry area
More than 50 tons of platinum are used annually to make jewelry. Most of the products sold contain 95% pure mineral. Since there are few impurities in the accessories, they do not fade, do not lose their beautiful silver color and retain their shine for a long time. Platinum is used to create beautiful necklaces, chains, bracelets, earrings, and rings.
Jewelry with a pure composition does not irritate the skin, as is often the case with accessories containing allergenic metals. The bright shine resembles a diamond shine. Platinum serves as an excellent setting for precious stones. It is often combined with natural yellow tones of gold.
Platinum jewelry is often chosen due to its high durability. Jewelry accessories made of gold and silver wear out after some time, and they have to be sent in for repairs to replace the deteriorated layer with a new one. This does not happen with platinum items, so they serve their owners for a lifetime.
Being in nature
Isotopes
Natural platinum occurs as a mixture of six isotopes: 190Pt (0.014%), 192Pt (0.782%), 194Pt (32.967%), 195Pt (33.832%), 196Pt (25.242%), 198Pt (7.163%). One of them is weakly radioactive (190Pt, alpha decay in 186Os, half-life 6.5⋅1011 years). The existence of very weak radioactivity of two more natural isotopes of platinum is predicted: the alpha decay 192Pt→188Os and the double beta decay 198Pt→198Hg, however, these decays have not yet been experimentally recorded; it has only been established that the half-lives exceed 4.7×1016 years and 3.2×1014 years, respectively.
Place of Birth
Platinum nugget, Conder deposit
Platinum is one of the rarest metals: its average content in the earth's crust (clarke) is 5⋅10−7% by mass. Even the so-called native platinum is an alloy containing from 75 to 92 percent platinum, up to 20 percent iron, as well as iridium, palladium, rhodium, osmium, and less often copper and nickel.
The bulk of platinum deposits (more than 90%) are located in the subsoil of five countries. These countries include South Africa (Bushveld complex), USA, Russia, Zimbabwe, China.
In Russia, the main deposits of platinum group metals are: Oktyabrskoye, Talnakhskoye and Norilsk-1 sulfide-copper-nickel in the Krasnoyarsk Territory in the Norilsk region (more than 99% of explored and more than 94% of estimated Russian reserves), Fedorova Tundra (Bolshoi Ikhtegipakhk site) sulfide- copper-nickel in the Murmansk region, as well as alluvial deposits Konder in the Khabarovsk Territory, Levtyrinyvayam in the Kamchatka Territory, the Lobva and Vyisko-Isovskoye rivers in the Sverdlovsk Region. The largest platinum nugget found in Russia is the “Ural Giant” weighing 7860.5 g, discovered in 1904 at the Isovsky mine; currently stored in the Diamond Fund.
Who knows the metal with the lowest density?
POS 61 tin 64%, lead 36% 181 T, P sodium 70%, mercury 30% 181 T Chem. act, Toxic. cadmium 32%, tin 68% 177(178) T, P Eutectic alloy lead 32%, tin 68% 177 T, P bismuth 12.8%, lead 49%, tin 38.2% 172 T, P potassium 80%, thallium 20% 165 T Chem. act bismuth 13.3%, lead 46%, tin 40.1% 165 T, P ∑? bismuth 10.5%, lead 42%, tin 47.5% 160 T, P bismuth 13.7%, lead 44.8%, tin 41.5% 160 T, P Eutectic alloy bismuth 16%, lead 36%, tin 48% 155 T, P bismuth 18.1%, lead 36.2%, tin 45.7% 151 T, P bismuth 25%, lead 50%, tin 25% 149 T, P bismuth 62.5%, cadmium 37.5% 149 T, P bismuth 19%, lead 38%, tin 43% 148 T, P bismuth 50%, lead 50% 145 T, P lead 32%, tin 50%, cadmium 18% 145 T, P bismuth 60%, cadmium 40% 144 T, P Eutectic alloy lead 42%, tin 37% 143 T, P ∑? cadmium 18.2%, lead 30.6%, tin 51.2% 142 8.8 T, P
Receipt
Native platinum is mined at mines (see the article Noble Metals for more details); placer deposits of platinum are less rich, which are explored mainly by the method of spot testing.
The production of platinum in powder form began in 1805 by the English scientist W. H. Wollaston from South American ore.
Today, 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 HNO3. In this case, iridium and palladium are reduced to Ir3+ and Pd2+. The subsequent addition of ammonium chloride produces ammonium hexachloroplatinate (IV) (NH4)2PtCl6. The dried sediment is calcined at 800–1000 °C:
3(NH4)2[PtCl6] →T 2N2↑ + 2NH3↑ + 18HCl + 3Pt
The sponge platinum thus obtained is subjected to further purification by repeated dissolution in aqua regia, precipitation of (NH4)2PtCl6 and calcination of the residue. The purified sponge platinum is then melted into ingots. When reducing solutions of platinum salts by chemical or electrochemical methods, finely dispersed platinum is obtained - platinum black.
Platinum for man
The scope of application of the precious metal includes the oil refining industry. Here you cannot do without catalysts containing platinum. The lion's share goes here (about half of the precious metal mined). The chemical industry uses the noble metal in the production of nitric acid.
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Platinum is indispensable in radio engineering, electrical engineering, telemechanics, and precision instrument making.
“Silver” is used in medicine. Here, surgical instruments are made from platinum alloys. There are methods for treating cancer using cis-isomers, derivatives of divalent platinum.
The activity of the Green Party has led to an increase in consumption of the “queen of metals” in the automotive industry. Tightening standards for harmful emissions into the atmosphere has led to the equipping of cars with autocatalysts.
The Russian kilogram standard is made from an alloy of platinum and iridium.
Informative: the police and casinos use platinum-coated mirrors. From the illuminated side it works like an ordinary mirror, from the shadow side it is transparent, like glass.
Physical properties
Grayish-white ductile metal, melting and boiling points - 2041.4 K (1768.3 °C) and 4098 K (3825 °C), respectively, electrical resistivity - 0.098 μOhm m (at 0 °C). Platinum is one of the heaviest (density 21.09–21.45 g/cm³; atomic density 6.62⋅1022 at/cm³) metals. Brinell hardness is 50 kgf/mm2 (Mohs 3.5).
The crystal lattice is face-centered cubic, and
= 0.392 nm,
Z
= 4, space group
Fm
3
m
.
Platinum is resistant to vacuum and can be used in space technology.
Density tables for metals and alloys
All metals have certain physical and mechanical properties, which, in fact, determine their specific gravity.
To determine how suitable a particular alloy of ferrous or stainless steel is for production, the specific gravity of rolled metal is calculated. All metal products that have the same volume, but are made from different metals, for example, iron, brass or aluminum, have different mass, which is directly dependent on its volume. In other words, the ratio of the volume of the alloy to its mass—specific density (kg/m3)—is a constant value that will be characteristic of a given substance. The density of the alloy is calculated using a special formula and is directly related to the calculation of the specific gravity of the metal. The specific gravity of a metal is the ratio of the weight of a homogeneous body of this substance to the volume of the metal, i.e. this is density, in reference books it is measured in kg/m3 or g/cm3. From here you can calculate the formula for finding out the weight of a metal. To find this you need to multiply the reference density value by the volume.
The table shows the densities of non-ferrous metals and ferrous iron. The table is divided into groups of metals and alloys, where under each name the grade according to GOST and the corresponding density in g/cm3 are indicated, depending on the melting point. To determine the physical value of specific density in kg/m3, you need to multiply the tabulated value in g/cm3 by 1000. For example, this way you can find out what the density of iron is - 7850 kg/m3.
The most typical ferrous metal is iron. The density value of 7.85 g/cm3 can be considered the specific gravity of iron-based ferrous metal. Ferrous metals in the table include iron, manganese, titanium, nickel, chromium, vanadium, tungsten, molybdenum, and ferrous alloys based on them, for example, stainless steel (density 7.7-8.0 g/cm3), black steel ( density 7.85 g/cm3) is mainly used by manufacturers of metal structures in Ukraine, cast iron (density 7.0-7.3 g/cm3). The remaining metals are considered non-ferrous, as well as alloys based on them. Non-ferrous metals in the table include the following types:
− light – magnesium, aluminum;
− noble metals (precious) - platinum, gold, silver and semi-precious copper;
− low-melting metals – zinc, tin, lead.
Chemical properties
Dissolving platinum in hot aqua regia
Platinum's chemical properties are similar to palladium, but exhibits greater chemical stability. At room temperature it reacts with aqua regia:
3Pt + 4HNO3 + 18HCl → 3H2[PtCl6] + 4NO↑ + 8H2O
Platinum dissolves slowly in hot concentrated 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 + 2Cl2 + 2NaCl → Na2[PtCl6]
When heated, platinum reacts with sulfur, selenium, tellurium, carbon and silicon. Like palladium, platinum can dissolve molecular hydrogen, but the volume of absorbed hydrogen and the ability to release it when heated is less in platinum.
When heated, platinum reacts with oxygen to form volatile oxides. The following platinum oxides have been identified: black PtO, brown PtO2, reddish-brown PtO3, as well as Pt2O3 and mixed Pt3O4, in which platinum exhibits oxidation states II and IV.
The hydroxides Pt(OH)2 and Pt(OH)4 are known for platinum. They are obtained by alkaline hydrolysis of the corresponding chloroplatinates, for example:
Na2[PtCl4] + 2NaOH → 4NaCl + Pt(OH)2↓ Na2[PtCl6] + 4NaOH → 6NaCl + Pt(OH)4↓
These hydroxides exhibit amphoteric properties:
Pt(OH)2 + 2NaOH → Na2[Pt(OH)4] Pt(OH)2 + 4HBr → H2[PtBr4] + 2H2O Pt(OH)4 + 2NaOH → Na2[Pt(OH)6] Pt(OH) 4 + 6HBr → H2[PtBr6] + 4H2O
Platinum hexafluoride PtF6 is one of the strongest oxidizing agents among all known chemical compounds, capable of oxidizing oxygen and xenon molecules:
O2 + PtF6 → O2 + [PtF6]−
The compound O2+[PtF6]− (dioxygenyl hexafluoroplatinate(V)) is volatile and decomposes with water into fluoroplatinate(IV), a small amount of hydrated platinum dioxide and oxygen with an admixture of ozone.
Using platinum hexafluoride, in particular, Canadian chemist Neil Bartlett in 1962 obtained the first true chemical compound of xenon, Xe[PtF6].
With the discovery of the interaction between Xe and PtF6 by N. Bartlett, leading to the formation of Xe[PtF6], the chemistry of inert gases began. PtF6 is obtained by fluorinating platinum at 1000 °C under pressure.
Fluoridation of platinum at normal pressure and temperature 350-400 °C gives platinum(IV) fluoride:
Pt + 2F2 → PtF4
Platinum fluorides are hygroscopic and decompose with water.
Platinum tetrachloride with water forms PtCl4 n
H2O, where
n
= 1, 4, 5 and 7. Dissolving PtCl4 in hydrochloric acid produces chloroplatinic acids H[PtCl5] and H2[PtCl6].
Platinum halides such as PtBr4, PtCl2, PtCl2 2PtCl3, PtBr2 and PtI2 have been synthesized.
Platinum is characterized by the formation of complex compounds of the composition [PtX4]2- and [PtX6]2-. While studying platinum complexes, A. Werner formulated the theory of complex compounds and explained the nature of the occurrence of isomers in complex compounds.
Reactivity
Coin 3 rubles, 1834
Platinum is one of the most inert metals. It is insoluble in acids and alkalis, with the exception of aqua regia. Platinum also reacts directly with bromine, dissolving in it.
When heated, platinum becomes more reactive. It reacts with peroxides, and upon contact with atmospheric oxygen, with alkalis. A thin platinum wire burns in fluorine, releasing a large amount of heat. Reactions with other non-metals (chlorine, sulfur, phosphorus) occur less actively. When heated more strongly, platinum reacts with carbon and silicon, forming solid solutions, similar to the iron group metals.
In its compounds, platinum exhibits almost all oxidation states from 0 to +6, of which +2 and +4 are the most stable. Platinum is characterized by the formation of numerous complex compounds, of which many hundreds are known. Many of them bear the names of the chemists who studied them (salts of Cossus, Magnus, Peirone, Zeise, Chugaev, etc.). A great contribution to the study of such compounds was made by the Russian chemist L. A. Chugaev (1873−1922), the first director of the Institute for the Study of Platinum, created in 1918.
Catalyst
Platinum, especially in a finely dispersed state, is a very active catalyst for many chemical reactions, including those used on an industrial scale. For example, platinum catalyzes the reaction of hydrogen addition to aromatic compounds even at room temperature and atmospheric pressure of hydrogen. Back in 1821, the German chemist I. W. Döbereiner discovered that platinum black promotes the occurrence of a number of chemical reactions; however, the platinum itself did not undergo changes. Thus, platinum black oxidized vapors of wine alcohol (ethanol) to acetic acid already at ordinary temperatures. Two years later, Döbereiner discovered the ability of spongy platinum to ignite hydrogen at room temperature. If a mixture of hydrogen and oxygen (explosive gas) is brought into contact with platinum black or spongy platinum, then at first a relatively calm combustion reaction occurs. But since this reaction is accompanied by the release of a large amount of heat, the platinum sponge becomes hot and the explosive gas explodes. Based on his discovery, Döbereiner designed the “hydrogen flint,” a device that was widely used to produce fire before the invention of matches.
Density of metals
This is the most numerous group of the periodic table. A metal is any substance that has high thermal and electrical conductivity, a characteristic surface shine when polished, and the ability to undergo plastic deformation.
This chemical element has low electronegativity compared to substances such as nitrogen, oxygen and carbon. This fact leads to the fact that in bulk structures metal atoms form metallic bonds with each other. It represents the electrical interaction between positively charged ionic bases and a negative electron gas.
Metal atoms are arranged in space in an ordered structure called a crystal lattice. There are only three types:
- cubic;
- BCC (body-centered cubic);
- HPU (hexagonal close-packed);
- FCC (face centered cubic).
The density of metals is a physical quantity that depends on the type of crystal lattice. Below is a table of this parameter for all chemical elements in g/cm 3, which under normal conditions are in a solid state.
It follows from the table that the density of metals is a value that varies over a wide range. Thus, the weakest is lithium, which, with the same volumes, is two times lighter than water. The density of the rare metal osmium is the highest in nature. It is 22.59 g/cm3.
Determination of product mass
All modern reference materials, GOST and technical specifications of enterprises have been adjusted in accordance with the international classification.
Using reference tables of densities of various materials, it is easy to determine their mass. This is especially true when items are heavy or appropriate scales are not available. To do this, you need to know their geometric parameters. Most often, you need to find out the mass of an object in the form of a cylinder, pipe or parallelepiped:
- Metal rods are cylindrical in shape. Knowing the diameter and length, it is easy to find out the mass. Mass equals density times volume. Finding the volume of an object. It is obtained by multiplying the cross-sectional area by the length. The area of a circle, knowing the diameter, is easy to determine. The squared diameter is multiplied by 3.14 (pi), divided by 4.
- We obtain the mass of the pipe in the same way. When finding the area, we take the difference between the outer and inner diameter of the section.
- To determine the mass of a sheet, bloom, slab or bar of rectangular cross-section, we determine the volume by multiplying the length, height and thickness. Multiply by the density from the reference book.
With such calculations, a small error is always allowed, because the shapes are not ideal. In practice it can be neglected. Manufacturers of metal products have developed special mass calculators for users. It is enough to enter unique dimensions in the appropriate windows and get the result.
