Element Name: Iridium
Atomic weight of element: 192.2
Element type: metal
Volume elastic modulus: GPa
320
Atomization enthalpy: kJ /mol @25℃
628
Heat capacity: J /(mol? k)
25. 10
Thermal conductivity: W/(m? k)
147
Conductivity: 10 6/(cm? Ω )
0. 197
Heat of fusion: (kj/mol)
26. 10
Heat of vaporization: (kJ/mol)
604.0
Atomic volume: (cubic centimeter/mole)
8.54
Density (g/cm3)
22.42
Content of elements in the universe: (ppm)
0.002
Content of elements in the sun: (ppm)
0.002
Content in the shell: (ppm)
0.000003
Oxidation state: main Ir+3, Ir+4.
Other Ir- 1, Ir0, Ir+ 1, Ir+2, Ir+5, Ir+6.
Crystal structure: the unit cell is a face-centered cubic unit cell, and each unit cell contains 4 metal atoms.
Cell parameters:
a = 383.9pm b = 383.9pm c = 383.9pmα= 90°β= 90°γ= 90°
Mohs hardness: 6.5
The speed of sound propagation in it: (m/s) 4825
Ionization energy (kJ/mol)
M-M+880M+-M2+ 1680 M2+-M3+2600 M3+-M4+3800 M4+-M5+5500 M5+-M6+6900
M6+-M7+8500 M7+-M8+ 10000 M8+-M9+ 1 1700
Discoverer: Tennant. Discovery date: 1803.
Discovery process:
1803, discovered by British Tennant.
Element description:
The first ionization energy is 9. 1 eV. Silvery white metal, hard and fragile. When hot working, as long as it is not annealed, it can be stretched into filaments and sheets; Once annealed, it loses ductility and becomes hard and brittle. The density is 22.42g/cm3. The melting point is 24 10 40℃ and the boiling point is 4 130℃. Face-centered cubic crystal. The chemical properties are very stable. Insoluble in acid. Slightly soluble in aqua regia; Slightly corroded by molten sodium hydroxide, potassium hydroxide and sodium dichromate. There is a strong tendency to form coordination compounds. The main valences are +2, +4 and +6.
Element source:
The content in the crust is only 9× 10-9%. It mainly exists in osmium iridium ore. It can be prepared by separating zinc from osmium-iridium alloy obtained when platinum is extracted.
Element usage:
Pure iridium is specially used for aircraft spark plugs, mostly used for making scientific instruments, thermocouples, resistance wires and so on. As an alloy, it can enhance the hardness of other metals. Its alloy with platinum (10% Ir and 90% Pt) is often used to manufacture international standard metric ruler because of its very small expansion coefficient.
Element auxiliary data:
Iridium is a platinum group element. Platinum series elements exist almost completely in a single state and are highly dispersed in various ores, such as primary platinum ore, nickel-copper sulfide ore, magnetite and so on. Platinum-based elements almost always coexist to form natural alloys. In ores containing platinum group elements, platinum is usually the main component, while the rest of platinum group elements must be found by chemical analysis because of their low content. Osmium, iridium, palladium, rhodium and ruthenium are all minerals with platinum, so they all exist in the residue after platinum is extracted from platinum ore.
Platinum group elements have stable chemical properties. Except platinum and palladium, they are not only insoluble in ordinary acids, but also insoluble in aqua regia. Platinum is soluble in aqua regia, and palladium is also soluble in hot nitric acid. All platinum elements have a strong tendency to form coordination compounds.
1803, French chemist Colade scottie and others studied the slag of platinum series ores dissolved in aqua regia. They announced that there were two new metals in the residue, which were different from platinum and insoluble in aqua regia. 1804, Denard discovered and named them. One of them is named irdium, and the symbol of the element is Ir. The word comes from the Greek iris, which means "rainbow". This may be due to the hydrate IrO2 of iridium dioxide? 2H2O or Ir(OH)4, when precipitated from the solution, is blue, purple, dark blue or black, which changes with precipitation.
Iridium (iridium)
The chemical symbol Ir, belonging to the transition element of Group VII of the Periodic Table of Elements, has an atomic number of 77 and an atomic weight of 192.2. It is a rare precious metal material with a face-centered cubic lattice.
A brief history 1803 iridium was found in the black residue after platinum separation in tennant, England; The first melting experiment of iridium was carried out in 18 13. 1860, Di 'e Mint smelted about 8kg of primary iridium-containing materials and other residues as raw materials to obtain an iridium ingot weighing 1.805kg. 188 1 year, J. Holland applied for an American patent named "Process for Melting and Casting Iridium". Since then, metallurgical workers in various countries have done a lot of work to solve the processing problem of iridium.
Properties The main properties of iridium are: (1) density of 22.65g/cm. , which is the highest density among known elements; (2) The melting point is 2454℃, and the service temperature of iridium products can reach 265438 0. 0 ~ 2200°C； (3) High elastic modulus (538.3GPa), low Poisson coefficient (0.26) and poor low-temperature plasticity; (4) It is the most corrosion-resistant metal. Dense iridium is insoluble in all inorganic acids and will not be corroded by other metal melts, such as molten lead, zinc, nickel, iron and gold. Resistant to corrosion of many molten reagents and high temperature silicates; (5) Iridium alloys, like other platinum group metal alloys, can firmly adsorb organic matter and can be used as catalyst materials; (6) IrO2 is generated by iridium in air or oxygen above 600℃ and decomposed at 1 100℃; The volatilization of iridium in air at 1227℃ is 0/00 times that of platinum. Iridium can be smelted by high frequency or intermediate frequency furnace, electric arc furnace, electron beam furnace, etc. Iridium has good plasticity above 1600℃ and is usually hot-worked.
The high melting point and high stability of iridium make it have important applications in many special occasions, but the brittleness and high temperature loss of iridium limit its application to some extent. Iridium was first used as a pen tip material, and later it was used as an injection needle, a balance blade, a compass bracket, an electric contact and so on. Iridium crucible can be used to grow refractory oxide crystals. The crucible can work for thousands of hours at 2100 ~ 2,200℃, and it is an important precious metal vessel material. The high temperature oxidation resistance and thermoelectric properties of iridium make the iridium/iridium-rhodium thermocouple the only precious metal temperature measuring material that can measure the high temperature of 2 100℃ in the atmosphere. Container materials that can be used as radioactive heat sources; Anodized iridium oxide film is a promising electrochromic material. Ir 192 is a gamma ray source, which can be used for nondestructive testing and radiotherapy and chemotherapy. At the same time, iridium is a very important alloying element, and some iridium alloys are used in some key sectors; Iridium compounds also have their unique uses.