The Mist And Mystique Of Dry Ice
Monday, October 21, 2013
Several prank bombs caused paranoia at Los Angeles International Airport last week. One -- packed in a 20-ounce soda bottle -- exploded in a restroom, one on the tarmac and a third was found just fizzling.
No one was injured.
A baggage handler, arrested for "possession of a destructive device near an aircraft," had assembled the simple, ordinary bombs using simple, ordinary material. The results inspired a flurry of concern. A few flights were delayed. An LAPD bomb squad, assisted by the FBI, marched in to investigate. The event made homepage news.
What is the simple, ordinary material that can elevate empty plastic bottles to the level of destructive -- and disruptive -- devices?
Two words: dry ice.
Witches And Weather
For nearly two centuries, dry ice has occupied a special place in the human imagination: It's the source of the chilled gas wafting over many a witch's cauldron at haunted houses. In some places, purchasing it is one of the rights imparted on teenagers when they turn 18, like the right to gamble or smoke. For a short time in the '40s and '50s, some meteorologists thought it was mankind's key to controlling the weather.
The mysterious substance is actually really simple. It's just frozen carbon dioxide. We know it mostly in its gaseous form -- the bubbles in soda, the breath we exhale, a measure of emissions. (It also supposedly performs as an exceptional mosquito trap, an acne treatment, a mold remover and in other minor miraculous ways.)
In its solid, frozen form, carbon dioxide can be mesmerizing. At -109.3 degrees Fahrenheit, it's so cold that it feels like a burn. It holds a special place in chemistry as the substance that is capable -- under normal atmospheric conditions -- of skipping from the solid to vapor state without ever becoming a liquid.
As the solid turns to gas, it expands -- just 1 pound of dry ice makes enough gas to fill scores and scores of 20-ounce soda bottles. If the reaction happens in a sealed container, the vapor buildup can lead to a pressure explosion.
Immune from wetness, it doesn't spill, trickle or drip. It just sublimates in an eerie, otherworldly gaseous slither.
Dry ice can also do deadly damage. In 1992, the Los Angeles Timesreported a glass bottle -- filled with dry ice -- exploded, killing a man with shards of glass.
Dry Ice Age
Solid carbon dioxide has shaped the surface of Mars, leaving signature cracks and dunes as seasonal carbon dioxide ice freezes on the ground in the fall and winter and then returns to its initial form come spring.
Here on Earth, dry ice entered scientific awareness in the 1830s, when a French chemist named Adrien-Jean-Pierre Thilorier wrote, "This result is truly amazing, and changes all our ideas about the expandability of bodies."
His descriptions sound ethereal. A "white flocculent powdery substance" gathers on glass surfaces, a solid piece "glides rapidly over a polished surface, as if it were raised by the gaseous atmosphere which constantly surrounds it, until it entirely disappears."
Since that moment, dry ice has been a hot commodity. Over the course of the last 178 years, it has spiced up parties, given theater productions excellent fog scenes, chilled organs en route to many a transplant, aided plumbers with tricky water pipe repairs, blast-cleaned industrial equipment, and even enabled early attempts at human cryopreservation.
But it has also been largely replaced by a cheaper, colder substance -- liquid nitrogen.
Still, dry ice abides.
As history would have it, in 1947 -- also in October -- dry ice was the central character in another airplane-related intrigue. In one of many experiments, scientists flew in a military plane along the edge of a hurricane building up off the coast of Florida and droppedcrushed dry ice into the clouds.
Instead, the westward-going hurricane changed its path, falling destructively on Savannah, Ga. Some angry locals blamed the dry ice for altering the hurricane's direction, though they couldn't confirm it because military officials refused to release flight details and scientific data.
And now, in unpopular culture, dry ice is known for its volatile potential.
Thilorier understood this property. In the process of traditional scientific inquiry, he discovered that if he put a little bit inside a glass jar with a rubber stopper, "the interior becomes filled with a thick vapour, and the stopper is soon driven out violently." The process is "so energetic that one gram of the substance produces an explosion as powerful as the same weight in gunpowder," he wrote in a letter to the French Academy of Sciences.
The dry ice bomb was born.
It could be said that when the baggage handler popped those bottles at LAX -- fortunately, in unpopulated spaces -- he was only pulling a prank, but he was also referencing that very strange moment in France years ago, when man met dry ice.
Copyright 2013 NPR. To see more, visit www.npr.org.
Please stay on topic and be as concise as possible. Leaving a comment means you agree to our Community Discussion Rules. We like civilized discourse. We don't like spam, lying, profanity, harassment or personal attacks.