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Potassium is an alkali metal, heavier and more reactive than sodium, but otherwise fairly similar both in pure form and in how it forms compounds. It's similar enough that potassium chloride serves as a substitute for sodium chloride, table salt, in foods intended for people who are on a low sodium diet.
Potassium plays many important roles in the chemical processes of life, including nerve impulse transmission. In all such situations, the potassium is in the form of K- ions, not elemental potassium. Like all alkali metals, potassium metal itself doesn't last long in the real world, reacting quickly with water or just moisture in the air to form potassium hydroxide and hydrogen gas (which then explodes).
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Salt substitute.
People who are supposed to restrict their sodium intake for health reasons can use potassium chloride instead of sodium chloride (salt) for seasoning. Potassium chloride is sold in every grocery store as one or another brand of "NoSalt", "Diet Salt", etc. Some are a blend of sodium and potassium chlorides, others like this one are nearly pure potassium chloride and/or other potassium salts.
This is by and large a good thing. As a reader, Phil Karn, has pointed out, potassium is a necessary nutrient, and for people with high blood pressure displacing sodium with potassium is an important step towards reducing it.
But interestingly, naturally occurring potassium contains a small but measurable fraction of potassium-40, which is radioactive. I bought a container of it expecting it to register barely, if at all, on our Geiger counter. Instead it is really quite unmistakable: A plate with about 4 tablespoons spread out registers over 400 counts per minute. Of course, one normally wouldn't eat that much at a time: Using a few assumptions about how much people might eat, I would guesstimate that steady use might result it doubling the average amount of background radiation you're normally exposed to. This is not significant considering that just living in certain cities, near a granite building, etc, will more than double the average background level. Interestingly, I have learned from Phil Karn that Issac Asimov long ago made a similar calculation: That the radiation dose from potassium in the body is roughly equal to the radiation dose from the other natural sources put together. This website has an interesting speculation about the role of potassium's radioactivity.
If you're currently using a salt substitute, please don't stop because of this information! The risk from radiation is utterly insignificant compared to the risk from high blood pressure. Furthermore, the amount of potassium in your body is probably about the same from day to day regardless of whether you're eating salt substitute or not. This is because the body needs a certain amount, and generally gets more than it needs in food whether you are using salt substitute or not: The excess is excreted efficiently.
Nevertheless, I'm keeping it in our Hot Box just for fun. It's a great demonstration of the importance of location: Outside the Hot Box it's just a container of salt, inside the Hot Box it's a real conversation piece.
There is a lot of interesting information about the surprising places you can find radiation in this book.
Source: Grocery Store
Contributor: Theodore Gray
Acquired: 27 August, 2002
Price: $6
Size: 6"
Purity: 52%
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Small rod.
Potassium is really not that hard to get, nor is it very expensive. But for some reason I just didn't have any for the longest time, until the very kind Max Whitby of the The Red Green & Blue Company put me out of my misery by sending me a sample from the element collection his company sells.
They sell a very nice element collection in several versions. Max Whitby, the director of the company, very kindly donated a complete set to the periodic table table.
To learn more about the set you can visit my page about element collecting for a general description or the company's website which includes many photographs and pricing details. I have two photographs of each sample from the set: One taken by me and one from the company. You can see photographs of all the samples displayed in a periodic table format: my pictures or their pictures. Or you can see both side-by-side with bigger pictures in numerical order.
The picture on the left was taken by me. Here is the company's version (there is some variation between sets, so the pictures sometimes show different variations of the samples):
Source: Max Whitby of The Red Green & Blue Company
Contributor: Max Whitby of The Red Green & Blue Company
Acquired: 20 January, 2003
Price: Donated
Size: 0.5"
Purity: 99.5%
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Sample from the Everest Element Set.
Up until the early 1990's a company in Russia sold a periodic table collection with element samples. At some point their American distributor sold off the remaining stock to a man who is now selling them on eBay. The samples (excepted gasses) weight about 0.25 grams each, and the whole set comes in a very nice wooden box with a printed periodic table in the lid.
To learn more about the set you can visit my page about element collecting for a general description and information about how to buy one, or you can see photographs of all the samples from the set displayed on my website in a periodic table layout or with bigger pictures in numerical order.
Source: Rob Accurso
Contributor: Rob Accurso
Acquired: 7 February, 2003
Price: Donated
Size: 0.2"
Purity: >99%
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