August 16, 2012
Bonding to Hydrogen: The simplest molecule, made for connection
Roald Hoffmann in American Scientist:
My first encounter with H2 was typical for a boy in the age of chemistry sets that had some zing to them. My set, made by A. C. Gilbert Co., contained some powdered zinc. It had no acids, but it taught you to generate them from chemicals it included (for instance HCl from NaHSO4 and NH4Cl), or—the manual said—you could buy a small quantity from your local apothecary. Perhaps I got it there, asking politely for the acid in my best accented English a year or so after coming to Brooklyn from Europe. I poured some of the dilute acid on the zinc in a test tube, watched it bubble away, lit (with some fear) a match and heard that distinct pop.
Next, I encountered the gas, Henry Cavendish’s inflammable air, in a high school electrolysis experiment. We ran a current through water with a little salt dissolved in it, collected the unequal volumes of gases formed, each trapped in an inverted tube. Both gases gave small pyrotechnic pleasures—one, hydrogen, with that satisfying pop when a newly extinguished splint came near it; the other, oxygen, revived exuberantly the flame of the same splint.
Primo Levi, in an early chapter in his marvelous The Periodic Table, describes an initiation into chemistry that features the same experiment, with more fearsome results:
I carefully lifted the cathode jar and holding it with its open end down, lit a match and brought it close. There was an explosion, small but sharp and angry, the jar burst into splinters (luckily, I was holding it level with my chest and not higher) and there remained in my hand, as a sarcastic symbol, the glass ring of the bottom.… It was indeed hydrogen, therefore: the same element that burns in the sun and stars, and from whose condensations the universes are formed in eternal silence.
Posted by S. Abbas Raza at 09:44 AM | Permalink