Inorganic
worldsfair | May 24, 2007"In food, both the acidity and the sugar content are important. Our taste responses comes from a balance of the two. Some foods have a low pH/high acidity but do not taste sour due to their high sweetener content. A good example of this is cola, which has pH ~3.50 but does not taste sour because of the high sweetener (or non-calorific sweetener if you drink diet) content."
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worldsfair | May 24, 2007"pH is an indication of how many hydrogen ions are present. The lower the pH the higher the hydrogen ion concentration. Hydrogen ion concentration is an indication of acidity. So a low pH is associated with acidity. Conversely a high pH is associated with alkalinity and is an indication of a low concentration of hydrogen ions."
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moleculeoftheday | April 19, 2007Carbon, with its four valence electrons, is in a unique position; its valence shells are exactly half filled. Compounds of elements with three valence electrons (such as boron) and elements with five valence electrons (such as nitrogen) can act very much like their carbon analogues. Boron nitride, ("BN") for example, can exist in a very hard form, much like diamond. Similarly, many semiconductors are based on combinations of groups III and V. Gallium aluminum arsenide, indium nitride, and aluminum arsenide, for example.
In a few cases, alternating boron-nitrogen compounds can act much like…
moleculeoftheday | January 18, 2007Nickel tetracarbonyl, like a lot of metal carbonyls, is an odd duck. Many complexes of metals and carbon monoxide don't act much like metal at all, and Ni(CO)4 isn't an exception. Nickel carbonyl is a liquid, but only just - it boils at 43C, or just above blood temperature. It's subject to lots of reactions, and just passing CO over impure nickel is a viable method of purifying nickel from a mixture (it will leave as the liquid or gas, depending on the temperature).
Unfortunately, it will give up that CO readily, including, as pointed out here, to certain vital enzymes, such as your…
moleculeoftheday | December 20, 2006Oxalic acid is a bifunctional carboxylic acid. Your body will make it as the result of metabolism of ethylene glycol if you ever drink antifreeze, resulting in the catastrophic precipitation of calcium oxalate in your kidneys. Some foods have (fairly low) levels of oxalate. A small portion of vitamin C/ascorbate is metabolized to oxalate, which is a very real concern if you're following Linus Pauling's lead and taking grams of the stuff per day.
moleculeoftheday | December 14, 2006You may have heard of a guy named Kurt Vonnegut. What you might not know is that his lesser-known little brother Bernie was the guy who came up with the idea of using AgI for cloud seeding.
From little bro Kurt's Timequake:
Question: What is the white stuff in bird poop?
Answer: That is bird poop, too.
So much for science, and how helpful it can be in these times of
environmental calamities. Chernobyl is still hotter than a Hiroshima baby
carriage. Our underarm deodorants have eaten holes in the ozone layer.
And just get a load of this: My big brother Bernie, who can't draw
for sour apples,…
moleculeoftheday | September 18, 2006Crown ethers are an unusual series of molecules that have the ability to complex small cations, notably alkali metals such as sodium and potassium. These cyclic molecules, upon complexing a cation, can allow a salt to go into organic solvent that otherwise wouldn't. This makes reactions that are otherwise impossible accessible.
A good example is how 18-crown-6 (shown below, an 18-membered ring with 6 oxygens/ether linkages) can help potassium permanganate (a beautiful purple oxidizing agent based on manganese (VII)) go into organic solvent. Normally, you can only get permanganate into very…
moleculeoftheday | August 30, 2006Ferrocene is another one of those weird molecules we just stumbled on. Upon reacting the anion of cyclopentadiene with an iron (II) salt, an "unusually stable" compound resulted. In inorganic chemistry, that often means stuff like stable to water or air, since much of this stuff falls apart gleefully.
The image doesn't quite do it justice; ferrocene is actually a "sandwich" of an iron (II) ion and two Cp rings, as you see here. A whole array of "metallocenes" was discovered later, but ferrocene is a classic. Many undergrad chem labs have you synthesize this (or the related, more sensitive…
moleculeoftheday | August 18, 2006There really isn't much to this one - Lead (II) Oxide has the forumula Pb (II) O, or PbO.
I started this entry intending to discuss how it was used in generating so-called "lead crystal." All Swarovski, Baccarat, etc., "crystal" is is regular silicon glass with up to about 20% lead oxide added. Lead oxide has a high refractive index (the amount by which the speed of light is retarded in the material compared to a vacuum; that is, a material of refractive index 2 would slow light to half the speed of that of light in a vacuum - refractive index 1).
Why would we want a high-refractive index…
moleculeoftheday | August 10, 2006Calcium carbide is something you don't see much anymore, but before electric light was ubiquitous and cheap, it was some amazingly useful stuff. Calcium carbide is a boring looking compound - I've only ever seen greyish lumps. It eacts like a salt of doubly deprotonated acetylene (C2H2, or here, more like C22-). Anything that reacts like (I say "reacts like" because it's surely a little more complicated than the structure I give below, but it's close enough for us) negatively charged carbon will be pretty basic, and tend to grab a proton wherever it can. One ubiquitous proton-bearing chemical…