Wednesday, January 04, 2006

The holidays have not been good to me!

Well I can't really say that I guess, the holidays were great to me. At the expense of my body that is. The lack of running coupled with the overabundance of tasty Christmas treats have done a number on me. I definitely feel a little soft in the midsection, and my pants fit just a little more tightly now. The most evidence for this is from my running though, today I was pooped after a 25 minute circuit. Granted I started off a little faster than I should have, but I was eager to get back into it. Plus, I got new shoes and I wanted to try them out.


When I first started running I did it in a pair of Big 5 $10 sneakers. After those wore out, I found a pair of Brooks trail runners at REI on special for $40. They happened to fit pretty well, but I think I got lucky on that. I ran in those for a year and a half. This year for Christmas I got a gift certificate to Runner's Roost, so I went in to actually be fitted for a proper running shoe. They checked my pronation (the motion of the foot from side to side when walking or running) and took a video of my feet on the treadmill while I ran. The result of all this was that the Brooks shoes seem to fit my foot pretty well (which is why I got lucky, the other shoes I tried did not fit well at all) but that I needed a shoe with more stability to support my feet a little better. Today was my first chance to get out and try them on the road. I'm glad that I decided to limit my distance though as these shoes need to be broken in a little, but I can feel a big difference in the support they offer. I'm looking forward to ramping up my miles this month in preparation for my marathon training.


I conducted a little experiment on Monday night that really appealed to my inner chemist. I polished our silverware. It does not get much use around our house, so it has never been polished before (almost 9 years now). Needless to say, some of it was in really bad shape. Being the lazy man that I am I have never really got into the idea of buffing each item to a shine. I remembered some years back reading about a method that cleaned the silver electrochemically, so I investigated further. It turns out that the reaction is a simple redox (reduction/oxidation) reaction. Silver tarnish is actually a reaction of silver with sulfur compounds from the atmosphere. Anywhere you get humidity with suitable concentrations of the byproducts of fossil-fuel combustion you get tarnish. This pretty much happens everywhere, but if you happen to live near an airport in California, you really get tarnish! The reaction that you want to have happen to reverse the tarnish is:


Ag2S + H+ + 2e- ⇔ 2Ag(s) + SH-



This is a reduction reaction (gain of electrons, reduction/loss of electrons, oxidation) with a half-cell potential of -0.272 V. In order to drive this reaction to proceed we need an oxidative process with a large positive half-cell potential. It turns out that the oxidation of aluminum is just such a reaction:


Al(s) ⇔ 3e- + Al3+



with a half-cell potential of 1.677V. Balancing the equation we get a redox reaction of:


3Ag2S + 2Al(s) +3H2O → 6Ag(s) + Al2O3+ 3H2S



Note that the generation of hydrogen sulfide gas means that it is a rather stinky reaction, but on the plus side all of the silver that was turned into tarnish is redeposited on your silverware, rather than ending up on a rag. So in order to get this reaction to go you just need to drop your silverware into a container lined with aluminum foil and filled with an electrolytic (i.e. salty) solution. It turns out that you also need to add a little baking soda to the mix in order to make the solution slightly basic. This softens up the oxidized aluminum on the surface of the foil and allows the bare aluminum to react more efficiently. Of course all reactions are not just about thermodynamics (as the designers of the Hindenberg knew), there is kinetics to think of as well (as the designers of the Hindenberg found out), so it doesn't hurt to add a little heat to the mix to help things move along. In the end, bringing a pot of water to a boil with a fair shake of baking soda and salt added, and pouring this over your silverware in a pan lined with aluminum foil, will leave your silverware shining brightly, and your kitchen smelling slightly of rotten eggs. This will leave you feeling vaguely suspicious that you are getting something for nothing, until you think of the huge amount of energy required to remove aluminum from bauxite ore, at which point you may think more seriously about recycling your aluminum cans.

2 comments:

melissa said...

So glad you blogged again! You had me until The reaction that you want to have.

Thanks for polishing the silver, I can't wait to use it with the new dishes. :)

Next post, you should talk about how you fixed the garage door.

lisa said...

holy crap! way too smart buddy. i am glad you are blogging again too! those new shoes sound pretty nice, especially to somebody whose feet hurt from wearing new ice skates :P