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Selenium

SeleniumMen, at least, have good reason to be grateful to Selenium. Experiments show that increased Se consumption is helpful to sperm production. We also come across Selenium as an addition to skin creams, shampoos and food supplements.

When it comes to metal trading, minor metal traders encounter Selenium mainly in one form – Selenium Metal Powder with a -200 mesh sieve size. This is the form in which it is marketed internationally once recuperated from anode slimes. However there is also frequent trade in what we might call Selenium Crude acid, which usually grades as Se 90% – material usually sourced direct as by-product from the mines. Se metal ingots, Se 99.99%, are produced in CIS, as well as granules that are illustrated on this page.

Areas of supply include Peru, Chile, Russia, China, Philippines and Finland mainly as by-product of Copper production. A market where Selenium is dominant is in pigments where Se gives the primary colour ‘red’ and is used with Cadmium Oxide (the primary colour ‘yellow’). The combination of the two creates the shades between red and yellow. Their success is that, unlike organic colours, these are indelible and, in some uses, therefore, irreplaceable.

Selenium FACTS

Selenium was discovered in 1817 by Jöns Jakob Berzelius. It is obtained in either a silvery metallic form (grey Se) or a red amorphous powder, which is less stable. Selenium burns in air and is unaffected by water. However, it dissolves in concentrated HNO3 and alkalis.

Growth in selenium consumption was driven by the development of new uses, including applications in rubber compounding, steel alloying, and selenium rectifiers. It is used to remove colour from glass, as it will counteract the green coloured ferrous impurities. It also can be used to give a red colour to glasses, enamels and even car paint. Selenium is also used to improve the abrasion resistance in vulcanized rubbers and plays an important role in photocopying.

Another use for selenium is the toning of photographs, and is sold by numerous photographic manufacturers including Kodak and Fotospeed. Its artistic use is to intensify and extend the tonal range of black and white photographic images, and it can also be used for increasing the permanence of images.

Selenium occurs as selenide in many sulfide ores, such as those of copper, silver, or lead. It is obtained as a byproduct of the processing of these ores, from the anode mud of copper refineries and the mud from the lead chambers of sulfuric acid plants. These muds can be processed by a number of means to obtain free selenium.

Atomic no.
Relative atomic mass
Melting point
Boiling point
Density
Young’s modulus
Heat capacity
Abundance
Thermal conductivity
34
78.96
221 oC
685 oC
4790 Kgm-3
10 GPa
25.363 J/K/mol
0.05 ppm
0.514 W/m/K