So you’re into sci fi? But what about sci fact? Sometimes fact is stranger than fiction…
Each month our very own Voyager Science Queen* will bring you interesting, quirky and downright bizarre tasty morsels from the world of science. And its all completely, totally, 100% true!
In the English language, ‘intumescent’ is a word that means distressfully or abnormally swollen, or something in the process of swelling. In chemistry, intumescents are substances that – upon the application of heat – result in the production of enormous amounts of ash, many times the volume of the original substance. This ash will be less dense than the original substance. In the past, intumescents have been used in pyrotechnics and in the production of fire retardants.Probably the most spectacular tumescent is mercury thiocyanate. Upon application of heat, this chemical expands and coils in a serpentine manner to form a yellowish or greyish mass of tentacular ash; it looks more like the hair of a Medusa to me. A quick surf of the internet will supply you with video clips of this spectacular process; it is referred to as the Pharaoh’s Serpent or the Pharaoh’s Snake. Mercury thiocyanate used to be a popular compound for fireworks, but its toxicity became an issue and it is no longer used as much.
When mercury thiocyanate is ignited, rapid oxidation causes it to decompose into carbon nitride, mercury sulfide and carbon disulphide. Notice the original substance contains a cyanide compound, sulfur and mercury, so it is extremely toxic, and the fumes released during the decomposition are poisonous. Even after its transformation, the ash is toxic enough to kill anyone ingesting it – like small children; tragedies have occurred. As interesting as this process is to observe, I would recommend just watching the video clips.
If I were a modern day alchemist and discovered mercury thiocyanate, I believe I would dedicate of this chemical to Cthulhu. However, it is suspected the first person to synthesize the compound was a chemist, Jöns Jacob Berzelius, in or around 1821. No pentacles or tentacles were involved … what a shame.
First off, let’s look at Newtonian fluids, so that we have a an idea as to why non-Newtonian fluids are so weird. A Newtonian fluid will remain a fluid regardless of the kinetic forces that are acting upon it, in other words, the viscosity of the fluid should be dependent on its temperature and pressure and not the forces action upon it. Water is the perfect example; if you stir or shake water it will remain a fluid, but a change in temperature or pressure can turn it into ice or steam.
This is not the case with non-Newtonian fluids. Under a sudden change in sheer forces, certain non-Newtonian fluids will lose viscosity and act like a solid. Cornflour (also known as corn starch) mixed with water acts in this manner. The faster you try to stir the mix, the stiffer it becomes … stop stirring and it slumps back into liquid. If you try to ‘throw’ a bucket of the mix, it will stay in the bucket. However, if you tip the bucket onto its side, the cornflour and water mixture will flow out like a fluid. As the water and cornflour mixture is entirely harmless, I can recommend playing around with it. I’ve seen the men from Mythbusters attempt to run across a pool of cornflour and water … with mixed results (pun intended); you can see this on: http://www.youtube.com/watch?v=5GWhOLorDtw
On ‘The Big Bang Theory’, our intrepid band of scientists used the vibrations of speakers to ‘stress’ a similar mixture: http://www.youtube.com/watch?v=2CJJ6FrfuGU
There are liquids that act in the exact opposite way to cornflour and water, like most house paints; they remain thick while at rest and become more fluid when stressed – or all the paint would drip off the walled once applied. These are non-Newtonian fluids as well, because their viscosity is affected by the kinetic forces acting upon them. Some polymer clays start out as quite stiff and become more elastic as they are ‘worked’; again, they can be classified a non-Newtonian fluid.
As an alchemist, I would rate a non-Newtonian fluid as super loony, but still pertaining to the element of water, so I would imagine it was ruled by the Moon. Or, if I may postulate a sixth element after fire, water, earth, air, and aether, and suggest they are just FUN!
*The Voyager Science Queen is also known as Lynne Lumsden Green- find out who she is in About Our Contributors!