iridium

Name iridium
Symbol Ir
Atomic Weight 192.217
Atomic Number 77
CAS ID 7439-88-5
Group Number 9
Group Name Precious Metal
Period Number 6
Origin of Name Latin, Iris = "rainbow."
Year Discovered 1803
Discovery Credits Discovered by S. Tennant at London, UK.
Class Metallic
Color Silvery White
Standard State Solid at 77 F & 298 K
Description Hard, lustrous, silvery metal of the platinum group. Stable to air and water, inert to all acids, but fused NaOH will attack it. Used in special alloys and spark plugs.

Diagnostic tests: 
There are no simple chemical tests for iridium. The element is usually found as an alloy or a sulfide mineral with other platinum group metals. Atomic Absorption Spectroscopy is used for quantitative analysis and Energy Dispersive Analysis of X-rays (EDAX) is used for qualitative analysis.

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