Inorganic
moleculeoftheday | September 24, 2008Yesterday, I discussed ammonium nitrate, an industrial fertilizer. One problem with it is its lavish reactivity. On its own, and particularly in combination with hydrocarbons, it makes a potent explosive - it was used in the attack on Oklahoma City in the 1990's.
Apparently, adding a different counterion makes a world of difference. This week, Honeywell reported a new fertilizer, Sulf-N26, which is just a mix of ammonium nitrate and ammonium sulfate. Apparently, it doesn't support the explosive combustion of fuel oil like pure ammonium nitrate does.
moleculeoftheday | September 15, 2008The camping series continues. Previously: octenol, the related octenone, and DEET. Today we move away from insects for the time being, turning our attention to water purification.Sodium hypochlorite, or NaOCl, is sold as an aqueous solution - laundry bleach. It is also a great disinfectant, and dilute bleach solutions are used by hospitals and IV drug users alike as a disinfectant.
A little bleach will disinfect water, too, but laundry bleach decomposes fairly rapidly (over periods of time as short as months). A shelf-stable source of hypochlorite is Ca(OCl)2 powder, which can be found in…
moleculeoftheday | July 18, 2008As was mentioned in the comments to my entry on a refrigerant Monday, what we use has changed quite a bit over the years. If you don't know how a fridge or AC works (they're the exact same thing), here's what happens: know how evaporation something makes things cooler (e.g., sweat?). Condensing something makes things hotter by the same principle. Refrigeration involves evaporating something and using the cold for what you want, then moving the vapor somewhere and compressing it (turning it into hot liquid) and dumping that heat somewhere else. Then you evaporate it again and get some more of…
moleculeoftheday | July 14, 2008I really, really love refrigeration. I will go so far as to say that it's the most important invention of the modern era. More than internal combustion, nuclear bombs and power, or electrification, refrigeration defines the US. If you're like most Americans, you preside over at least THREE refrigeration units - one in the house, one in the kitchen, one in the car. The Central Valley in CA, DC, Las Vegas, Phoenix, Dallas, Houston, Atlanta - a huge swath of the country would look very different without AC. Not to mention your grocery store.
Awhile back, we began getting concerned about the…
moleculeoftheday | May 27, 2008I love stuff like this. A lot of people don't believe that water is blue until they see some really clean water. It really is, though, and the reason is simple yet fascinating. It is because water is blue - very faintly, it's a unique phenomenon because you don't see 10,000 gallon pools of methanol (etc.).
D2O, for example, is not blue.
To see some really brilliantly blue water, take a look at these incredible frozen wave glacier pictures.
Thanks for all the corrections; here is some moving water that does freeze.
moleculeoftheday | May 19, 2008Mica is neat, you might remember it as the really flaky stuff you used during the minerals demo in grade school:
(Public domain wikipedia image)
The coolest thing about mica is that it makes a great substrate for AFM. If you take a sheet of mica and put it between two pieces of scotch tape, and pull them apart carefully, you will cleave the mica. This releases some ancient air that has been ensconced between the sheets for a few billion years (correct me if I'm off by a few orders of magnitude) and gives a perfectly atomically flat surface.
moleculeoftheday | April 20, 2008Oscillating reactions are neat; I should write up one of my favorites sometime... Here, electrons flow from iron metal to mercury (I) sulfate to chromium (VI) oxide. Listen to the video for a step-by step explanation...
moleculeoftheday | January 17, 2008Lead and chromium (VI) - you can't do much better for toxicity.
The lead (II) salt of chromium (VI) oxide gives a vivid yellow. Before organic dye technology became robust, we were stuck with metal salts for color. This means metals. Unfortunately, there are more toxic metals than nontoxic metals, so you were stuck in a tough place there - especially if you wanted to make, say, a yellow baby rattle.
moleculeoftheday | December 27, 2007Everyone by now has tried products like OxiClean, or detergents with "oxygen bleach." Rather than sodium hypochlorite, which is found in regular bleach, they've got sodium percarbonate, which is actually a mixed crystal of sodium carbonate (the old-timey name of which is "washing soda") and hydrogen peroxide. In solution, they form a "peracid," peroxymonocarbonate.
Speaking very generally, a bond between two electronegative atoms is the business end of an oxidant - the oxygen-oxygen bond in hydrogen peroxide and peroxymonocarbonate does the job there, and the oxygen-chlorine bond is the…
moleculeoftheday | October 26, 2007Mercury dissolves many metals. Put a little on normally steadfast aluminum and it will slowly eat it away. Mix it with some silver, copper, and other metals, and you've got a dental filling. Mix it with sodium, and you've got a great reducing agent.
Sodium amalgam acts much like sodium, but it's got the added advantage of being a liquid - since reactions require collisions, you're not limited by the small surface area of a solid. Paradoxically, it's actually a little safer and less explodey than sodium. Unfortunately, the mercury part makes it a bit of a liability for, say, pharmaceuticals or…
moleculeoftheday | October 25, 2007The term "rare earth metal" is a misnomer that's just stuck around. They haven't been rare for years - take this ad material from about 50 years ago at Theodore Gray's excellent Periodic Table Table site.
Didymium is a mixture of rare earth metals, which, when compounded with glass, imparts some color. Metals used to be pretty much our only way of imparting color. For quantum mechanical reasons, the enormous middle swath of the periodic table can impart some brilliant colors.
Modern organic dye technology has advanced like crazy, but metals are alive and well. Your green and brown glass have…
moleculeoftheday | October 23, 2007Mischmetal is a mixture of a some rare earth metals, mostly cerium and lanthanum. The cerium, when finely divided, is pyrophoric - it burns.
When you mix mischmetal with some iron and magnesium oxides, it's a lot more brittle, and you can chip off little flakes, which give sparks. That's your lighter flint.
moleculeoftheday | October 2, 2007Nitinol is an alloy of nickel and titanium. It can do some neat stuff:
Nitinol exhibits "shape memory" - which is an advertising-type name, really. This just means it's not permanently deformable below a critical temperature, above which it will "remember" its shape, upon cooling. For this reason, it's been called a "smart metal" and has been used in dentistry and orthodontia (gotta find something good to hold up to those caramels the kids keep eating...).
Travelling the rest of the week and back next Monday.
moleculeoftheday | September 20, 2007The previous entry on cyclohexadiene reminded me of another important piece in some hydrogenations - Raney nickel.
If you have an alloy of nickel and aluminum, and put a chunk of it into a sodium hydroxide solution, you'll end up dissolving the aluminum selectively (generating some hydrogen gas along the way). You'll end up with a little aluminum, mostly nickel, with a high surface area and quite a bit of hydrogen gas adsorbed to the nickel - true to periodic theory, Ni acts much like Pd and Pt with respect to hydrogen.
Raney nickel comes as a slurry in water - if you let it get dry in air,…
moleculeoftheday | September 12, 2007Electrons are reactive guys when they're on their own, and tricky to isolate. If you take a bit of fur and rub it on some amber, you end up with a surplus of electrons, but they won't hang around long (the reason I mention amber is because this is what the Greeks used - the word electron comes from the Greek for amber). This is kind of cheating, though, you just have a surface with surplus electrons. Actually isolating them is tricky. If you're a poor scientist like me and use a CRT you found by the Dumpster, your monitor has an electron gun, and you actually have some ephemeral isolated…
moleculeoftheday | August 30, 2007Mellitic anhydride is unusual - as mentioned in the argument over urea, it seems like it should be organic - it's a benzene derivative - but there's no hydrogen. This causes it to fail some peoples' tests for whether something's organic.
More bafflingly, mellitic acid's aluminum salt is a mineral! Mellite sure looks like a rock, huh?
moleculeoftheday | August 15, 2007Chloroauric acid is obtained by the oxidation of gold in the presence of chloride, as in aqua regia.
Chloroauric acid is central to one of the sweetest stories in science, ever: hiding Nobel prizes from the Nazis. From the old blog:
My very favorite story about aqua regia is this: during World War II, a Hungarian chemist living in Denmark, George de Hevesy, dissolved two fellow scientists' Nobel Prizes in aqua regia literally as the Nazis stormed into Copenhagen so they wouldn't be stolen (he assumed, correctly, that the Nazis would just leave the chemicals alone). After the war, he…
worldsfair | May 24, 2007"Intermolecular forces are the forces between molecules, whereas intramolecular forces are those within molecules. (The bonds that hold the atoms in a molecule together are intramolecular forces.) A quick note before we jump in: When chemical educators are explaining intermolecular forces, they almost always use examples of intermolecular attractions..."
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worldsfair | May 24, 2007"When multiple atoms are part of an assembly in which they are bonded to each other, you have a molecule. For the moment, consider the "bond" between atoms in a molecule to be an electron-sharing arrangement that maintains a certain (average) spatial configuration between the nuclei of the bonded atoms..."
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worldsfair | May 24, 2007"An element is defined by the number of protons in the nucleus. The element oxygen has 8 protons in the nuclei of its atoms. Any atom (or radical or ion) that has exactly 8 protons is an oxygen atom, and all oxygen atoms (or radicals or ions) have exactly 8 protons. It doesn't matter how many electrons there are zipping around the nucleus; that determines the net charge.."
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