History of Iridium
(L. iris, rainbow) Smithson Tennant discovered iridium in 1803 in the residue left when crude platinum is dissolved by aqua regia. The name iridium is appropriate because its salts are multi-colored.
Iridium, a metal of the platinum family, is white, similar to platinum but with a slight yellowish cast. Because iridium is very hard and brittle, it is hard to machine, form, or work.
It is the most corrosion-resistant metal known, and was used in making the standard meter bar of Paris, which is a 90 percent platinum and 10 percent iridium alloy. This meter bar was replaced in 1960 as a fundamental unit of length.
Iridium is not attacked by any of the acids nor by aqua regia, but is attacked by molten salts, such as NaCl and NaCN. The specific gravity of iridium is only very slightly lower than osmium, which is generally credited as the heaviest known element. Calculations of the densities of iridium and osmium from the space lattices give values of 22.65 and 22.61 g/cm3, respectively. These values may be more reliable than actual physical measurements. At present, therefore, we know that either iridium or osmium is the densest known element, but the data do not yet allow selection between the two.
Iridium occurs uncombined in nature with platinum and other metals of this family in alluvial deposits. It is commercially obtained from osmiridium a by-product of platinum production. It is also recovered as a by-product from the nickel mining industry.
Although its principal use is as a hardening agent for platinum, iridium is also used to make crucibles and devices requiring high temperatures. It is also used for electrical contacts and is slowly finding it way into medical devices that are implanted into the body.
The element is also alloyed with osmium and is used for fountain pen nibs and compass bearings.
Fabrication and Forms
Iridium is generally available as wire spooled onto spools or random length piece rod, strip, ribbon, foil or sheet. It is usually rolled from plate and slit to required widths which is the reason for the random lengths as the material is very hard to fabricate without many intermediate anneals to keep the material somewhat ductile. H. Cross Company can provide this material in wire sizes from .005″ diameter up to .100″ diameter, strips and ribbons from .0005″ thick to .020″ thick and from .020″ to .100″ wide and in sheet or foil form from .0005″ thick to .020″ thick and up to 2″ wide. Please Contact Us if you have needs outside of these ranges, as we will always try to be of assistance for your specific requests.
Each H. Cross Company product is delivered in packaging specifically designed for the product’s application. As an example, wire is furnished on returnable plastic reels, each containing a single length of wire measuring 10 feet minimum. Strips, Ribbons, Sheets and foils are flat packed to prevent damage during shipping. If required, H. Cross Company can adapt standard packaging methods or develop new ones for your special needs.