i*rid"i*um(*rd"*m), n. [NL., fr. L. iris, iridis, the rainbow. So called from the iridescence of some of its solutions. See Iris.] (Chem.) A rare metallic element of atomic number 77, of the same group as platinum, which it much resembles, being silver-white and indifferent to most corrosive agents, but harder, more brittle, and with a higher melting temperature (2410 C, versus platinum 1772 C). With the exception of osmium, it is the heaviest substance known, its specific gravity being 22.4. Symbol Ir. Atomic weight 192.22.
[1913 Webster +PJC]
Iridium usually occurs as a native alloy with osmium (iridosmine or osmiridium), which may occur alone or with platinum. Iridium, as an alloy with platinum, is used in bushing the vents of heavy ordnance. It is also used for the points of gold pens, and in a finely powdered condition (iridium black), for painting porcelain black.
New - Add Dictionary Search to Your Site
You can add a free dictionary search box to your own web site by copying and pasting the following HTML into one of your web pages:
<form action="http://www.freedict.co.uk/search.php" method="post"> <p style="text-align: center; font-family: sans-serif;"> <a style="font-weight: bold;" href="http://www.freedict.co.uk/" title="FreeDict free online dictionary">FreeDict</a> <input type="text" name="word" size="20" value="" /> <input type="submit" name="submit" value="Search Dictionary" /> </p> </form>
Sat 15th December 2018