Periodic Table -> Osmium


Osmium Details

Osmium Symbol: Os

Osmium Atomic Number: 76

Osmium Atomic Weight: 190.2

What is Osmium?

Osmium (atomic number 76, symbol Os) is a brittle, hard metal that belongs to the platinum family. The element has several oxidation states - +8, +3, +2, etc. Besides osmium, the +8 oxidation state has been reported for several elements only - plutonium, iridium, xenon, and others. Osmium has a very high density and low compressibility. It is difficult to process or form when in solid state due to its high melting point and hardness.

Osmium is a lustrous, silvery metal which is unaffected by acids, water, and air at room temperature. Solid osmium dissolves with molten alkalis, but the spongy or powdered metal releases osmium tetroxide. Osmium tetroxide is very toxic and can cause eye and skin damage and lung congestion.

The extraction of the metal is time-consuming and complex. In ores, osmium occurs mixed with silver, ruthenium, and other metals. The extraction of other metals such as platinum and rhodium is often the main goal, with osmium being a byproduct. Preliminary treatment is necessary so that other metals can be removed.

Osmiridium and iridosmine are the most important ores of osmium. Iridosmine, which is a rare mineral, is mined in South and North America and Russia. The production of osmium is less than 100 kg a year. Generally, iridosmine contains a larger percentage of osmium.

Depending on the composition and the type of separation method being used, there are different ways to extract osmium. One technique is through fusion with sodium peroxide and another is through dissolution in hydrochloric acid. Treatment with sodium hydrogen sulfate is then required. The mixture contains iron, osmium, and ruthenium, and sodium oxide is used to treat it. Iron is insoluble and produces osmium and ruthenium salts which are water-soluble.

The metal is used as a catalyst in different alloys. It is used in alloys because of its volatility and high toxicity. The alloys of osmium are hard and are mainly used in electrical contacts, pivots of instruments, and nib pens. An alloy of 10 percent osmium and 90 percent platinum is used for pacemakers and other surgical implants. While potassium osmate and osmium tetroxide are poisonous, they are used as oxidants for chemical synthesis.

The metal is typically sold in the form of a 99 percent pure powder. It is measured in grams and troy ounces similar to other precious metals. Its price depends on the supplier and the quantity offered.

Osmium tetroxide is a very toxic compound which should be handled by experienced chemists only. The compound can enter the body by ingestion or by inhalation of its vapor or aerosol. Inhalation causes shortness of breath, wheezing, headache, cough, and visual disturbances. Skin burns result in blisters or skin discoloration. Osmium tetroxide can cause eye damage, which results in loss of vision, blurred vision, and pain. If the compound is absorbed by ingestion, this can lead to burning sensation, cramps, collapse, or shock. Repeated or long term exposure is dangerous. The compound is toxic and causes damage to the respiratory tract, the skin, and the eyes. Prolonged or repeated exposure may cause lung oedema and dermatitis. Corn oil or other vegetable oils can be used to reduce osmium tetroxide to an inert compound.

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