Imagine you are predicting the weather with the Weems Stormglass

The Weems Stormglass, it is called. Not some steampunk confection, this strange little device, invented more than two centuries ago, is said to predict the weather by the forms taken by its mineral-heavy liquid. Spreading crystal ferns indicate storms, while a clear phial means it will remain calm. In all weather, you pay $149.99 for it.

"No-one knows quite how it works," says crapvendor Signals. "But it does."

[#1 posted by shutz , October 6, 2008 7:54 PM]

"No-one knows quite how it works,"

Heh. It's a barometer. It reacts to minute changes in barometric pressure. Since the crystals form when a storm is coming, it means low pressure causes crystals to form, and high pressure causes them to dissolve.

Not knowing the exact composition of the crystals and solution, my only guess is that the substances involved must be of a kind similar to water ice crystals, where too much pressure breaks certain weak bonds between molecules (which is why water ice will turn liquid if you apply pressure to it, but metals and most other solids don't.)

If you're a chemist and know more about this sort of thing, please post, as my own chemistry classes are over 10 years in my past...

[#2 posted by arkizzle , October 7, 2008 5:20 AM]

Shutz

Not that I know, but: surely If you put enough pressure on metal, it will heat and liquify.. no?

[#3 posted by arkizzle , October 7, 2008 5:22 AM]

Or indeed, if the metal in question was at a temperature as close to melting as water is in its solid state (20~º), when you apply the pressure.

[#4 posted by Arvidsem , October 7, 2008 5:33 AM]

Probably not. I think (not a chemist) ice turns to water when it is compressed because water ice is less dense than water liquid. Most metals are more dense in their solid form than they are in their liquid form, so they will not liquefy under pressure.

[#5 posted by CyclotronBoy , October 7, 2008 5:35 AM]

Rob!
Actually, Weems is just the manufacturer. The Storm Glass was invented by Admiral Robert FitzRoy and used on his trip with Darwin on the HMS Beagle. The glass is filled with a nearly supersaturated solution of potassium nitrate and ammonium chloride with water, ethanol and camphor. Here's some background:
http://en.wikipedia.org/wiki/Storm_glass
and a DIY project waiting to happen:
http://chemistry.about.com/od/weirdscience/a/fitzroy.htm

-Fred

[#6 posted by Anonymous , October 7, 2008 6:50 PM]

Damn shame someone has spammed this story

http://sugarmob.com/2008/10/07/imagine-you-are-predicting-the-weather-with-the-weems-stormglass/

I thought you may be interested in this. I did a Google for Weems Stormglass. BBG was #1 and this blog was #2.

[#7 posted by arkizzle , October 17, 2008 12:21 PM]

I presumed that pressure == heat, and therefore would lead to shiny liquid goodness.