December's Element of the Month:
Atomic Mass: 126.90447 amu
Melting Point: 113.7 °C
Boiling Point: 184.3 °C
It turns out that, contrary to what I thought, Iodine is not a blue liquid. That would probably be Iodide, an Iodine compound commonly used as a disinfectant, as it was manifested in my elementary school. Iodine is a disappointingly silver metal, but with a twist -- it ablates (I believe is the term) into a purple haze at temperatures low enough that you could produce them on your stovetop. Really! A purple haze! It is, I think you'll agree, a pretty neat trick.
(I thought it was interesting that people talk about metallic silver Iodine and gaseous purple Iodine, but don't have much to say about the 70 degree span in which it is a liquid. Apparently, it can be a little hard to see the liquid for the purple mist that immediately starts forming over the top of it. Awesome. Photographic evidence suggests it looks a bit like Mercury.)
Iodine's biggest claim to fame is that it is the heaviest Element with an important biological role (with an asterisk for Tungsten, which is heavier and is important in some bacteria, but probably not so much in you and me). Lack of Iodine in your diet can throw your thyroid off, and also cause a number of problems at the level of your individual cells. Iodine deficiency is, we're told, the "biggest preventable cause" of mental retardation; if the thyroid isn't behaving well during development, it can lead to cognitive deficits.
Iodine is found in its greatest concentration on your kitchen table. It's added to table salt by almost every manufacturer, and quite a few countries require salt iodization despite the protests of small-scale salt producers, makers of Iodine tablets, and people with extremely sensitive palettes who convince themselves that they can detect a difference in the taste. Like the fluoridation of water, an idea that is still a subject of cringe-inducing debate here in the City of Roses, this draconian manipulation of the food supply by sinister government forces has dramatically raised the quality of life for countless millions. In places with Iodine-poor soils, such as say in the American Pacific Northwest, thyroidal problems and associated intellectual disabilities were once rampant (something, I'm sorry to say, that is clearly evidenced in the Michael5000 family tree). Iodised salt pretty much eliminated that. Happily, an ever-increasing number of countries, notably Kazakhstan -- another naturally Iodine-poor area -- are in the process of replicating the experiment.
Outside of table salt, Iodine generally appears in a highly water soluble state. That means there are very few concentrations on land, but plenty in the ocean. And that, in turn, explains why there would be large areas of the map that are deficient in a mineral that lots of animals are all dependent on. When the basic wiring map for our brains was being drawn up, we were still in the briney deep where there was always Iodine available. Once we crawled up on dry land, things were always going to be a bit hit-or-miss, Iodine-wise.
Oops, I almost forgot the history bit! Iodine was discovered during the Napoleonic wars by Bernard Courtois, a saltpeter producer. One step of the saltpeter production process involved pouring sulfuric acid on seaweed ash -- long story -- and, under pressure to produce as much saltpeter as possible, Courtois dumped more than the usual amount of acid into the ash, and was surprised (who wouldn't be?) by the cloud of purple vapor. M. Courtois had the presence of mind to crystallize out some of this odd stuff, and even suspected he had a new Element on his hands, but recognized that he didn't have the facilities or funding to study it properly. So, he sent samples out to some chemists he knew, and before long there was the usual conflicting claims over who had completed the relevant labwork first. Everybody graciously conceded, however, that Courtois deserved most of the credit.