All about iridium

Most people have a pretty good idea of ​​iron and aluminum, silver and gold. But there are chemical elements that play a slightly smaller role in the life of the modern world, but are undeservedly little known among non-specialists. It is important to correct this flaw, including learning everything about iridia.

It should be said right away that iridium is a metal. Therefore, it has all the properties that are typical for other metals. Such a chemical element denoted by a combination of Latin characters Ir. In the periodic table, it occupies Cage 77. The discovery of iridium took place in 1803, as part of the same study in which the English scientist Tennant also isolated osmium.

The initial raw material for the production of such elements was platinum ore delivered from South America. Initially, the metals were isolated in the form of a precipitate, which "aqua regia" did not take. The study revealed the presence of several previously unknown substances. The element received its verbal designation because its salts look as if iridescent with a rainbow.

Chemically pure iridium has no rainbow color. But it is characterized by a rather attractive silvery-white color. Toxic properties have not been confirmed. However, certain iridium compounds can be hazardous to humans. The fluoride of this element is especially poisonous.

A number of Russian and foreign enterprises are involved in the production and refining of iridium. Almost the entire production of this metal is a product of by-processing of platinum raw materials. Although iridium is not purple, it naturally contains 2 isotopes. Elements 191 and 193 are stable.But a number of artificially obtained isotopes have pronounced radioactive properties, their half-life is short.

The strength and hardness of iridium is very great. It is almost impossible to process this metal mechanically. Infusibility this element is silvery white in color is large enough. Specialists include iridium in the platinum group. The hardness on the Mohs scale is 6.5. The melting point in degrees reaches 2466 degrees. Iridium, however, begins to boil only at 4428 degrees. The heat of fusion is 27610 J / mol. Boiling heat - 604000 J / mol. Experts have determined the molar volume at 8.54 cubic meters. see for a mole.

The crystal lattice of this element is cubic, the edges of the crystals are the tops of the cube. The 191st isotope accounts for 37.3% of iridium atoms. The remaining 62.3% is represented by the 193rd isotope. The density of this element (or otherwise, the specific gravity) reaches 22400 kg per 1 m3.

But the atoms of iridium themselves rarely enter into any reactions. This element is distinguished by its outstanding chemical passivity.... It is completely insoluble in water and does not change in any way even after prolonged contact with air. If the temperature of a substance is less than 100 degrees, then it will not react even with aqua regia, let alone other acids and their combinations. The reaction with fluorine is possible at 400 degrees; for the reaction with chlorine or sulfur, it is necessary to heat the iridium until it becomes red hot.

There are 4 known chlorides, in which the number of chlorine atoms varies from 1 to 4. The effect of oxygen is noticeable at temperatures not lower than 1000 degrees. The product of this interaction is iridium dioxide, a substance practically insoluble in water. The solubility can be increased by oxidation using a complexing agent. The highest oxidation state under normal conditions can be achieved only in iridium hexafluoride.

At extremely low temperatures, compounds with valences of 7 and 8 appear. The formation of complex salts (both cationic and anionic) is possible. It is noted that highly heated metal can corrode hydrochloric acid saturated with oxygen. Chemists attach an important role to:

• hydroxides;
• chlorides;
• halides;
• oxide;
• to iridium carbonyls.

Obtaining iridium in nature is greatly hampered by its great rarity. In the natural environment, this metal is always mixed with related substances. If this element is found anywhere, then platinum or metals from its group must be found nearby. Some ores containing nickel and copper include iridium in dispersed form. The main part of this element is extracted from inert matter in:

• SOUTH AFRICA;
• Canada;
• the North American state of California;
• deposits on the island of Tasmania (owned by the Australian Union);
• Indonesia (on the island of Kalimantan);
• different areas of the island of New Guinea.

Iridium mixed with osmium is mined in old mountain folds located in the same countries. Companies from South Africa... It is not without reason that the production in this country directly affects the balance of supply and demand, which cannot be said about products from other regions of the planet. According to existing scientific concepts, the rarity of iridium is due to the fact that it came to our planet only in meteorites, and therefore it accounts for a millionth of a percent of the mass of the earth's crust.

However, some experts disagree with this. They insist that only a small part of all iridium deposits are explored and suitable for development at the level of modern technologies. Sediments, which appeared in deep geological antiquity, contain in separate layers of iridium hundreds of times more than the rocks already being mined.

Today, iridium is mined only after the end of the extraction of the main minerals.... These are gold, nickel, platinum or copper. When the deposit is close to depletion, the ore begins to be processed with special reagents that release ruthenium, osmium, and palladium. Only after them comes the turn of receiving the "rainbow" element. Further:

• refining ore;
• crush it into powder;
• this powder is pressed;
• pressed workpieces are remelted in electric furnaces, with continuous movement of an argon jet.

A fairly large amount of metal is recovered from the anode sludge left by the copper-nickel production. Initially, the sludge is enriched. Platinum and other metals, including iridium, are converted into solution under the action of hot aqua regia. Osmium ends up in the undissolved sediment. Complexes of platinum, iridium and ruthenium are successively precipitated from the solution under the action of ammonium chloride.

About 66% of the iridium mined used in the chemical industry... All other sectors of the economy share the remainder. In recent decades, the jewelery value of the "purple metal" has been steadily growing.... Since the late 1990s, rings and inlaid gold jewelry have been periodically made from it. Important: jewelry is made not so much of pure iridium as of its alloy with platinum. A 10% additive is enough to increase the strength of the workpiece and the finished product up to 3 times without a significant increase in cost.

In other industries, iridium alloys are also clearly ahead of pure metal. The ability to increase the hardness and strength of products by a minor addition is very much appreciated by technologists. Thus, iridium additives are used to increase the wear resistance of wire for electronic tubes. The hard metal is simply laid over molybdenum or tungsten. Subsequent sintering takes place under a press at a high temperature.

And here it is necessary to say especially about the use of iridium in the chemical industry. There, his alloys are needed to obtain dishes resistant to various reagents and high temperatures. Iridium also turns out to be an excellent catalyst. An increase in reactivity is especially evident in the production of nitric acid... And if you need to dissolve gold in aqua regia, then technologists are almost guaranteed to choose exactly the cups made of platinum-iridium alloy.

Where they cook crystals for laser devices, you can often find platinum-iridium crucibles. Completely pure metal is suitable for parts of high-precision industrial and laboratory instruments. The iridium mouthpiece is used and glazierswhen they need to make refractory glass. But this is only a small part of the applications of the amazing element.

Experts have long noted that such candles last longer.... At the very beginning, they were used primarily for sports cars. Today they have become cheaper and are available to almost all car owners. Iridium alloys are also needed by creators surgical instruments... They are increasingly used in the manufacture of individual parts of the pacemaker.

It is curious that the “10 francs” coin produced in Rwanda is made of gem-quality (999 standard) iridium. This metal is also used in automobile catalysts. Like platinum, it helps to accelerate the purification of exhaust gases. But you can find iridium in the most common fountain pen. There you can sometimes see an unusual colored ball on the tip of a pen or ink rod.

Iridium was mainly used in radio components several decades ago. More often contact groups were made of it, as well as components that can be very hot.This solution allows you to ensure the durability of products. The isotope iridium-192 is one of the artificial radionuclides. It is produced for non-destructive use to check the characteristics of welds, steel and aluminum alloys.

An alloy of osmium with iridium is used to make compass needles. And thermocouples, which combine iridium and conventional electrodes, are used for physical research. Only they can directly register a temperature of about 3000 degrees. The price of such structures is very high. It is not economically feasible to use them in conventional industry.

Iridium Titanium Electrode - one of the relatively new developments in the field of electrolysis. The refractory substance is sprayed onto a titanium foil base. In this case, only argon is in the working chamber. The electrodes can look like a grid or a plate. Such electrodes:

• resistant to high temperatures;
• resistant to significant voltage, density and current;
• do not corrode;
• more economical than electrodes with the addition of platinum (due to a significantly longer resource).

Small containers with radioactive isotopes of iridium are in demand in metallurgy. Gamma rays are partially absorbed by the charge. Therefore, it is possible to determine what is the level of the charge inside the furnace.

You can also point to such applications of the 77th element as:

• obtaining molybdenum and tungsten alloys, which are stronger at high temperatures;
• increasing the resistance of titanium and chromium to acids;
• production of thermoelectric generators;
• manufacture of thermionic cathodes (together with lanthanum and cerium);
• creation of fuel tanks for space rockets (alloyed with hafnium);
• production of propylene based on methane and acetylene;
• an additive to platinum catalysts for the production of nitrogen oxides (precursors of nitric acid) - but this technological process is no longer very relevant;
• obtaining reference units of measurement (more precisely, this requires a platinum-iridium alloy).

Iridium salts are very varied in color. So, depending on the number of attached chlorine atoms, the compound can have copper-red, dark green, olive or brown colors. Iridium difluoride is colored yellow. Compounds with ozone and bromine are blue in color. Pure iridium has very high corrosion resistance even when heated to 2000 degrees.

In rocks of terrestrial origin, the concentration of iridium compounds is very low.... It increases significantly only in rocks of meteorite origin. This criterion allows researchers to establish important facts about various geological structures. Only a few tons of iridium is produced on earth.

For other properties and uses of iridium, see the next video.