This blog is my attempt to reconnect with the world of chemistry. I have a PhD in Inorganic Chemistry and make a living doing research for a large company in Michigan. As times have changed, that company has changed its focus and I no longer have as much chance to do the basic, fundamental research which I most enjoy. Through this blog, I am hoping to recapture the magic which I felt during my graduate (and undergraduate) days in college. Expect topics on chemistry and alchemy along with some non-chemistry related items which I think might be interesting.

"The chymists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasure among smoke and vapour, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I would change places with the Persian King."

Johann Joachim Becher (phlogistonist)
Acta Laboratorii Chymica Monacensis, seu Physica Subterranea, (1669).

Thursday, February 21, 2008

Missing Ammonia Chemistry

Cats are great pets, but having them around means occasionally having to deal with cat pee. Years ago I had a male cat that for some reason began to spray inside the house. The problem eventually resolved itself, but not before I had plenty of urine-soaked towels that needed to be cleaned (or burned). Without thinking too much about it, I threw them in the washing machine along with some bleach. Now even my wife knows not to mix ammonia and bleach, but I didn’t make the connection until a rather noxious odor began emanating from the laundry room. Apparently, the amount of nitrogen in those towels was considerable.

While airing out the house, I was struck by the fact that I was unaware of the actual chemical reaction that had occurred. AFAIK, it had never been mentioned in any of my chemistry classes. In fact, I do not recall ever hearing much about ammonia chemistry at all, other than vague statements about ammonia being the nitrogen analogue of water. We covered amines in organic chemistry, but that was about it. Apparently, the chemistry of ammonia was just not considered important enough to teach. Other than using a metric ton of ammonium hydroxide over the years for raising pHs or making transition metal ammine complexes, I really had not had much interaction with ammonia. Anyway, as most of you probably already know, the ammonia/bleach reactions are:

NH3 + HOCl → NH2Cl + H2O Toxic
NH2Cl + HOCl → NHCl2 + H2O Toxic
NHCl2 + HOCl → NCl3 + H2O Toxic and explosive

(Cat urine is mostly urea, I believe, but apparently Cl2 can react with that too.)

In retrospect, I should have been aware of these reactions based on my “familiarity” with their iodine analogues. NI3 is prepared using ammonia and iodine in exactly the same manner. Once dry, a slight touch is often sufficient to cause it to explode, producing a loud crack and a plume of purplish smoke. It’s probably fairly difficult to make it through undergraduate chemistry without learning this reaction (perhaps less so for organic chemists who have their own set of explosive materials with which to work). I admit to having used NI3 in rather unprofessional ways as an undergraduate, but I was an amateur compared to the guy down the hall, who was known for producing rather large batches of NI3 for his entertainment. My closest encounter with NI3 occurred one evening, when this guy stopped by my lab to ask if I had enjoyed “the show.” Seeing the puzzled look on my face, he pointed to the various undetonated piles of NI3 he had left throughout the lab which, by some miracle, I had managed to avoid. He also pointed to what appeared to be the remains of an already detonated batch of NI3 on the inside of the doorknob - remains that I attempted to brush off with my finger. Well, my finger only tingled for a little while and it took some work to remove the iodine coating my hand, but otherwise I was no worse for wear. Needless to say, that guy never brought NI3 into my lab again.

We definitely need to start teaching ammonia chemistry in school again.

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