Indium is a fusible, very soft and malleable metal with a silvery tint. It is the 49th element of the fifth period of the table of chemical elements, where it is designated by the symbol In (Indium). Its properties are similar to those of aluminum and gallium, while its appearance is similar to that of zinc. It takes its name from the indigo-colored shade of the spectral line characteristic of indium.

History

In 1863, German scientists Reich and Richter obtained an indigo line in the spectrum during a spectral study of zinc dipstick. The scientists were looking for gallium, which gives the spectral line a green color, but discovered a new element instead. Separated in its pure form, indium turned out to be very malleable - much softer than lead, 20 times softer than gold. The French Academy of Sciences valued a tiny pencil-shaped ingot of the new metal at one hundred grams at $80,000. Four years later, for the 1867 World's Fair, India was represented by a half-kilogram ingot. Today the price of this metal is about $700 per kg. Global consumption of indium increases every year. In 2010 it reached 900 tons.

Mineralogy

Indium is found as a dispersed impurity in a wide range of minerals. Its content in high-iron sphalerite is a few grams per kilogram, in chalcopyrite and stannite it isThe total content of indium in the Earth's minerals is several grams per kilogram. The total content of indium in the Earth's crust is about 0.25 g/t. It is even higher in seawater, at 18 g/t.

Getting

It is believed that there is no useless waste in chemistry. The technology of obtaining indium from industrial waste provides proof of this. The very history of its discovery is associated with an ore called "zinc dross". At present indium is obtained from intermediate wastes of zinc, tin, copper and lead production. Although they only contain trace amounts of indium, up to 0.1%, and it is quite a difficult task to separate it from accompanying elements - cadmium, zinc, copper, antimony and others - but it is worth it: indium is indispensable. The first concentration step is to separate it from copper, zinc, and cadmium. The raw material is treated with sulfuric acid, which dissolves the metals, and the concentrate is separated by hydrolytic precipitation. This is accomplished by changing the acidity of the solution. Cadmium hydroxide precipitates at a pH of about 8, zinc and copper hydroxides at 6. To "precipitate" indium hydroxide, the pH of the solution should be brought to 4. "Rough indium" is extracted from the concentrate by cementation on zinc and aluminum. "Pure indium" is obtained by refining using zone melting.

Purity grades

An interstate standard, GOST 10 297-94, which regulates the quality of produced indium in ingots, pyramids and rods, has been in effect in the former Soviet Union since January 1, 1997. According to the standard, this metal is produced in five purity classes depending on the percentage of the element. Thus In0000 grade contains this element in the amount of 99.9999%. In000, the percentage of pure indium is 99.9995%. In00 has 99.999%. In0 has a chemical purity of 99.998%. And In2 grade is 99.97%.

Properties

The density of indium at 20 °C is 7.362 g/cm³. Whereas magnesium ignites at 623 °C, indium withstands heating to 800 °C, after which it flashes a violet-blue flame and forms an oxide. This metal is soluble in almost all acids, faster in inorganic acids (especially easily in chlorine and nitrogen). It is stable in alkali solutions but reacts with bromine and chlorine and reacts with iodine, sulfur and phosphorus vapors when heated. Critical temperature of superconductivity of indium = 3.405°C.

Applications

• As an acceptor additive to silicon and germanium in microelectronics.
• For fusible solders. The exceptional adhesion of indium to many materials allows soldering of, for example, metal with glass.
• In the production of glass for liquid crystal monitors.
• Coating mirrors and car headlights with indium gives reflectivity at the same level as silver, while being more resistant to atmospheric influences.
• For graduation of thermocouples.
• For photocells.
• As a phosphor.
• Indium coating of aluminum skirts of diesel pistons reduces wear.
• Indium arsenide is a high temperature high performance thermoelectric, doped with 10% indium phosphide to increase efficiency.
• Isotopes 111In and 113In are used in radioisotope diagnostics.
• Indium isotope 115In - for detecting neutrinos with a threshold energy of 120 keV: 115In + νe → 115Sn+e-+2γ
• Indium is part of the "blue gold.

Global consumption of indium is growing rapidly in the 21st century, reaching 900 tons in 2009. It is indispensable in high vacuum applications as a gasket (gaskets, coatings); in particular, in sealing of spacecraft and elementary particle gas pedals. The electrochemical indium-mercury oxide system serves to create batteries with high specific power capacity. The indium-silver alloy is resistant to hydrogen sulfide and serves to create high-quality reflective coatings. Its alloys with gallium, tin and zinc melt at room temperature and can be liquid metal coolants. Indium absorbs thermal neutrons and can serve to control nuclear reactions. Even better in this role are its compounds with other elements that capture neutrons. Indium oxide is used to produce thermal neutron absorbing glass. The best known composition of such glass is indium oxide (12%),.boron oxide (33%), cadmium oxide (55%). Indium, which has a low melting point, is indispensable in the production of liquid crystal screens and as a component of fusible solders and alloys. Indium orthophosphate is a component of dental cements

Supplies

Indium is shipped by road. Shipments are transported by rail at the rate of 1 freight piece per consignee. Marks In000 and In00 are transported in ingots or pyramids with weight from 50 g to 1 kg. For other grades - up to 3 kg. If necessary In000 ingots may weigh 20-50 grams, while Czochralski method ingots may weigh up to 2.5 kg. In00 grade is supplied in bars of Ø 21-25 mm and length of 50-70 mm, or Ø 22-24 mm and length of 63-67 mm.

Minor surface defects are acceptable within the limits specified by the standard. Each ingot is marked. Indium ingots In000 and In0000 are each packed separately in polyethylene packages In00 and In0 ingots may be packed in pairs. In2 ingots are packed either in polyethylene film or in waxed paper.

Buy at a bargain price

Evek GmbH has a wide range of rare metal products in stock. We supply indium products at the best prices. Technical documentation on products includes data on the chemical composition, the limiting percentage of impurities, mechanical properties of products, the quality of the surface. Attached the results of ultrasonic testing. Lead time is minimal. For wholesale customers there are preferential discounts.