When first dissolved in HCl, Ir revealed such hues,
So rare it sits in Pt’s group, corrosion it eschews.
Help’d set our standard length and mass,
In plugs it sparks with hard-nosed class.
Surmise the fate of dinosaurs from Ir’s bound’ry clues.

(pronunciation guide for chemical formulas: “HCl” = aytch-see-ell, “Ir” = eye-arr)

When first dissolved in HCl, Ir revealed such hues,

GROUP 9 TRANSITION METAL

Iridium is a hard (yet brittle), lustrous metal that sits at the crossroads of row 6 and group 9 on the periodic table. English chemist Smithson Tennant discovered iridium in 1803. Tennant named the element after Iris, the Greek goddess of rainbows: he noted, “I should incline to call this metal iridium, from the striking variety of colors which it gives, while dissolving in marine acid.” Marine acid is a version of muriatic acid, which is one of the old names for hydrochloric acid (HCl).

(pronunciation guide: “Pt’s” = pee-tees)

So rare it sits in Pt’s group, corrosion it eschews.

[eschew: verb — to avoid, to shun]

Iridium is extremely rare. It comprises just 3 parts per trillion (ppt; that is, just 3 g per 1,000,000,000,000 g) of Earth’s crust, making it only the 84th most abundant element on the planet. Despite its scarcity, iridium is a valued member of the elite platinum group of metals because it resists corrosion better than any other metal on the periodic table.

Help’d set our standard length and mass,

Iridium’s acclaimed corrosion resistance prompted its use in initially defining the metric system: it accounts for 10% of the platinum-iridium alloy used to make the standard meter rod and the standard kilogram cylinder. Both standards have been conserved at the International Bureau of Weights and Measures (Bureau International des Poids et Mesures (BIPM)) in Paris, France, since 1889.

The standard meter rod remained the accepted prototype until 1960. It was then replaced by a more accurate definition based on a particular wavelength of light emitted by krypton. A further revision in 1983 defined the meter relative to the speed of light in a vacuum.

The standard kilogram cylinder remained the International Prototype of the Kilogram (IPK) until May 2019. The kilogram was then redefined with reference to the Planck constant (h), a fundamental constant in quantum physics equal to exactly 6.626 070 15 × 10^–34 J s. This new definition hinges on the units of the Planck constant, joule second: J s = kg m² s^–1. Because the second (s) and the meter (m) have fixed numerical values, fixing the value of the Planck constant effectively ties the definition for the kilogram (kg) to one of nature’s constants. (The second is defined with respect to a particular hyperfine splitting frequency of the cesium atom.)

In plugs it sparks with hard-nosed class.

Iridium is used on the tips of high-grade spark plugs where its renowned hardness prolongs the plugs’ sparking lifetime for up to 100,000 miles.

(pronunciation guide: “Ir’s” = eye-arrs)

Surmise the fate of dinosaurs from Ir’s bound’ry clues.

It has been speculated that a meteor strike on Earth some 65 million years ago produced an apocalyptic dust cloud. The cloud caused so much of the sky to darken to such an extent (and for so many seasons) that most creatures couldn’t survive. Although this theory might or might not fully (or even partially) explain dinosaur extinction, evidence for it comes from two sources: first, from the thin layer of iridium present in the rocks deposited on the planet around this time (at the boundary layer between the Cretaceous and Tertiary geological periods), and second, from the fact that meteors are known to be much richer than Earth’s crust in heavier metals like iridium.

The Author

Peter Davern is a lecturer in the Department of Chemical Sciences at the University of Limerick, Ireland.
He wrote a five-line poem for each element, with an explanation after each line of what is unique or exciting about that element.

Reference

The poem and explanation have been taken out of the book:

From Arsenic to Zirconium – Poems and Surprising Facts about the Elements
by Dr. Peter Davern
No Starch Press, San Francisco, CA, USA, May 2020, 296 pp.
ISBN-13: 9781718500273

Also of Interest

Book Review: How to Remember Quirky Elemental Facts

Peter Davern wrote a five-line poem for each element, with an explanation after each line of what is unique or exciting about that element—Why did he do so?