Friday, December 19, 2014

Element of the Month: Caesium!

December's Element of the Month:


Atomic Mass: 132.90545196 amu
Melting Point: 28.5 °C
Boiling Point: 671 °C

The first thing that struck me about Caesium is that it has a very low melting point, 28 degrees Centigrade, which is 82 degrees Unitedstatesian. This made me think that it would be great for building temporary backyard winter shelters, not unlike igloos, that would melt away in the fullness of late spring. Unfortunately for my scheme, it turns out that Caesium is also highly pyrophoric, which is to say that it bursts into flame when exposed to air. It also reacts explosively with water. So much for the Caesium yurt craze.

Caesium is also the “softest” of the elements, an abstract concept that made me think that maybe it would be a good metal for making pillows. But then it occurred to me that human body heat would melt the Caesium and that your head would slowly sink right through it, the same problem that plagues pillows made of butter. Plus, the pyrophoric thing and the explosive reactions with water would be a problem with this innovation, too.

The Centerfold!

Some Caesium being kept in an airtight, waterproof container, what with the pyrophoric thing.

By the way, if you are wondering if Caesium is the same thing as Cesium, the answer is yes. Calling it Cesium is an American eccentricity, like calling Aluminium Aluminum. You can call it c├Žsium if you really want to be cool, and know how to produce an aesc. Or an "ash," as it is sometimes called. But I digress.

It’s the 45th most common element on the Earth’s crust and has some unusual mineralogical properties, but we won’t go there. Most of the Caesium used by the human community comes from Manitoba. It’s used for this and that, but not really for much. Its sexiest use, if you swing that way, is in the technical definition of the second. You thought the definition of a second was “1/60th of a minute” or “1/86,400 of a mean solar day,” but the first is circular (because a minute is 60 seconds) and the second is fuzzy (because, what’s a mean solar day anyway, and will it never change?). No, the definition of a second is:
the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.
“What we can’t do in this age of marvels!” we exclaim, before realizing that this definition has been in place since 1967.

Robert Bunsen and Gustav Kirchhoff discovered Caesium in their mineral water in 1860. They were looking for it pretty hard with the spectroscope they had recently invented together. They named it after the Latin word for “sky blue,” not because it or any of its minerals are sky blue – which, bummer, because that would be cool – but because its spectroscopic emission spectrum makes bright blue lines. On a roll, the team of Bunsen and Kirchhoff would go on to discover Rubidium in 1861. Bunsen and his lab tech developed the “Bunsen burner,” a legacy if ever there was one. Kirchhoff coined the concept of “black body radiation” and has a couple of minor laws of physics named after him, which is also pretty good.

Long-time friend to the blog Calico Cat recently called my attention to
The Period Table in Fabric.  Here's its representation of this month's
Element, by North Dakota quilter Kim Stenehjem.

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