So I decided to try washing it. Some gentle detergent, cool water, and no agitation, and I had a soft, lovely sweater. Mostly. Because I wear this sweater for heavy exercise, the armpits were, shall we say, still seeming fresh off the bike.
I tried searching the Ravelry forums, and a few of my usual online resource haunts, but everything that talked about deodorizing wool seemed to be concentrating on unfortunate incidents involving pets and wool rugs. Keeping in mind the few weeks I spent in chemistry, I didn't think that methods for removing odors from mammal excrement could be used for removing odors from human sweat--maybe I was wrong--I hope I'll never know!
So I turned to the manual for all things domestic in my abode: Home comforts : the art & science of keeping house by Cheryl Mendelson. Her recommendation: baking soda.
Keeping my chemistry in mind, I double-checked: baking soda is alkaline, and my detergent is alkaline. How does it work? As with everything in the book, she explains:
As a deodorizer, [baking soda] works neither by perfuming or masking odors nor by absorbing them. It chemically neutralizes odors ... most unpleasant odors are caused by strong acids ... or strong alkalies ... Baking soda reacts with the odor molecules to bring them to a more neutral pH ... the deodorant effect is also present when baking soda is dissolved in water ...
Of course I have no idea if that's what actually happened in my basin, but with a much-darned sweater from Goodwill, I was willing to experiment. (I would never try any of this with my handknits--those go straight to Sam's Cleaners!) A few tablespoons of Bob's Redmill's baking soda and some cool water in my small basin, and about ten minutes of soaking, followed by adding some gentle detergent for another soak, and, voila! A completely deodorized, fluffy, soft, sweet smelling sweater!