Platinum, commonly known as platinum, with atomic number of 78, is one of the precious metals in Group VIII, the sixth cycle of the periodic table of elements.[1]Platinum belongs toPlatinum series element, atomic weight 195.05, density 21.45g/cmthree, melting point 1772 ℃, boiling point 3827 ℃.[6]
Platinum is mainly distributed inColumbia、U.S.A、CanadaOntario andRussiaUral.[5]Pure platinum has good high-temperature oxidation resistance and chemical stability, and is easy to process.[3]Platinum is mainly used in jewelry, anticancer drugs, chemical catalysts, platinum electrodes, corrosion resistant utensils and special alloys.[8]
The reaction activity of platinum is very low, so it usually does not cause harm.But all platinum compounds are highly toxic.[5]
Two billion years ago, a huge meteorite formed by the explosion of a star hit the earth, and various rare and precious metals appeared on the earth, from which platinum was born.[6]
In 1735, when Uloa, a Spaniard, went to Peru as a scientific expedition, he found a piece of hard to process metal in the gold mine, which looked like silver, so he named it Platinum.[1]
In 1741, Wood, a metallurgist from Jamaica, Latin America, first brought platinum samples to Britain for research. After being studied by scientists from Britain, Sweden, Germany, France and Spain, he aroused great interest in Europe. Because of the high melting point of this metal, it is difficult to smelt, and the natural platinum contains iron and copper,The problem of product ductility has not been greatly improved.[7]
In 1748, British chemist Watson confirmed platinum as a new element.[1][6]
In 1785, Chabeneau, a physicist and Fausto de Elhuyar, a chemist in Belgara, Spain, proposed a method to obtain a certain amount of ductile platinum.
In 1820, the British chemist David invented the platinum wire alcohol lamp. Platinum played a catalytic role in the oxidation reaction of alcohol, so the platinum wire alcohol lamp can emit very bright light, which can be used for lighting. This lamp has been popular in Europe for many years.[1]
1822, RussiaUral MountainsA large amount of platinum was found.[5]
Physical and chemical properties
Announce
edit
physical property
Platinum is a silvery white lustrous metal[2], melting point 1772 ℃, boiling point 3827 ℃, density 21.45g/cmthree(20 ℃), soft, with good ductility, thermal conductivity and conductivity.Sponge platinumIt is a gray spongy substance with a large specific surface areacarbon monoxide）It has strong absorption capacity.Powdered platinum black can absorb a lot of hydrogen.The chemical property of platinum is inactive and stable in air and humid environment. When heated below 450 ℃, the surface will formPlatinum dioxideThe film can react with sulfur, phosphorus and halogen at high temperature.Platinum is insoluble in hydrochloric acid, sulfuric acid, nitric acid and alkali solutions, but soluble in aqua regia and molten alkali.The oxidation state of platinum is+2,+3,+4,+5,+6.Easy to formCoordination compound, such as Pt (NHthree)twoCltwo、K[Pt(NHthree)Clfive]。
Physical properties of platinum
Element Name
platinum
Symbol
Pt
CAS No
7440-06-4
Atomic weight
one hundred and ninety-five point zero five
Atomic volume
9.10（cmthree/mol）
The content of elements in the sun
0.009（ppm）
Content in the crust
0.001（ppm）
Content of elements in seawater
Pacific surface 0.00000011 (ppm)
Mohs hardness
4 - 4.5
The propagation rate of sound in it
2800（m/s）
Oxidized state
+4 (main), 0,+2,+5,+6
Layout of peripheral electronic layer
5dnine6sone
Electronic layer
K-L-M-N-O-P
chemical property
Reaction of platinum with halogen
Platinum andFluorine gas（Ftwo）The reaction can be carried out under controlled conditions to generate volatileplatinum hexafluoride （PtFsix）Or platinum tetrafluoride (V) [(PtFfive)four]。The structure type of the latter is the same as (IrFfive)four、(RhFfive)four、(OsFfive)fourAnd (RuFfive)fourAnd will be disproportionated intoPlatinum tetrafluoride（PtFfour）。[5]
Similarly, under controlled conditions, platinum (Ⅱ) chloride (PtCl) can be generated by the reaction between platinum and chlorinetwo）。[5]
Reaction of platinum with aqua regia
Although aqua regia can dissolve platinum, this is related to the state of platinum. Dense platinum dissolves very slowly in aqua regia at room temperature, and platinum wires with a diameter of 1mm can be completely dissolved in 4-5 hours.When heated, platinum black (platinum powder) can react with concentrated sulfuric acid to generate Pt (SOfour)two、SOtwoAnd water.Chloroplatinic acidThe method of preparation is to dissolve platinum metal in aqua regia.The product of this reaction is HtwoPtClsix, rather than platinum compounds previously thought to contain nitrogen.Chloroplatinic acid is a reddish brown solid, which can be obtained by evaporating its solution.
Preparation method
Announce
edit
Platinum bars
To prepare platinum, first useAqua regiaFor ore or productionBase metalBy products afterPretreatmentTo obtain gold and platinum (such as HtwoPtClfour）Solution of the complex.Add to the solutionFerrous chlorideThe gold can be precipitated and separated from the solution.Add NH to the solutionfourCl，Platinum can be converted into (NHfour)twoPtClsixIn the form of HtwoPdClfourRemain in solution.Sponge like crude platinum can be obtained by combustion precipitation.Re dissolve the crude platinum with aqua regia, and then add it to the solutionSodium bromideSolution to removerhodiumandiridiumImpurities.Then joinammoniaTo make platinumAmmonium chloroplatinateThe form of precipitation.Finally, by burning the compound, platinum can be obtained.[5]
application area
Announce
edit
Industrial use
Platinum is widely used in catalysts, sensors, anticancer drugs, petroleum refining, electronic equipment manufacturing and other fields.For example, it is used to produce computer hard disks to increase the storage capacity of multilayer ceramic capacitors and hybrid integrated circuits;Production of glass for LCD;Used as dental restorative materials.[1]
Platinum based catalyst
Platinum based catalysts are mainly divided into "pure platinum catalysts" and "platinum alloy catalysts" according to whether they contain other metals.Pure platinum catalyst has high activity and good stability, and can be mass produced in actual industry.However, the high cost of pure platinum catalyst restricts the commercial development of PEMFCs.Platinum alloy catalyst can effectively reduce platinum loading and improve catalyst activity. It is still in the stage of laboratory research and development. The preparation process is complex, and the consistency of structure and performance is poor, which makes it difficult to quantify production.[1]
Medical use
Platinum anticancer drugs are indispensable in cancer chemotherapy. They have very obvious clinical effects on many solid tumors, such as ovarian cancer, prostate cancer, testicular cancer, lung cancer and so on.There are four platinum anticancer drugs on the market: cisplatincarboplatin 、OxaliplatinandNedaplatinThere are also some new drugs under development, such as cycloplatinumLobaplatin, thioplatinum, etc.Different drugs have different characteristics and different effects.[6]
Distribution
Announce
edit
Platinum mining
Platinum is often dispersed together with other platinum group elements in a variety of minerals in alluvial deposits and alluvial deposits.In nature, platinum exists in both free and combined forms. Common platinum containing minerals areArsenoplatite, antimony platinum ore, sulfur platinum ore, sulfur nickel palladium platinum ore, sulfur platinum palladium ore, etc.The total reserves of platinum group resources in the world are 69700 tons, including 63000 tons in South Africa, 3900 tons in Russia, 1200 tons in Zimbabwe, 900 tons in the United States, 400 tons in China, and 31300 tons in Canada.[1]
The global platinum reserves are very limited. In recent years, the main domestic production has also continued to decline.In 2019, South Africa (130 tons) was still the country with the largest platinum output, but the output has continued to decline for three years;The country with the second largest output is Russia (22 tons), which has basically maintained the output of about 22 tons in the past five years;This was followed by Zimbabwe (15 tons), Canada (7.4 tons) and the United States (3.6 tons).From the above data, it can be seen that the platinum production of South Africa and Russia mines is almost monopolized, and China also imports platinum mainly from South Africa and Russia.[1]
Safety measures
Announce
edit
Toxicological data
The reaction activity of platinum is very low, so it usually does not cause harm.But all platinum compounds are highly toxic.[5]
Storage and transportation
Store in a sealed container in a cool, dry place away from oxidants.[4]
