Day: April 29, 2014

Tuesday, 29 April 2014

10:05 – Among other things yesterday, I filled and capped several hundred bottles for biology kits. I’ll do several hundred more today.

First up is Seliwanoff’s Reagent Part A, which is simply a dilute solution of resorcinol (AKA 1,3-dihydroxybenzene or m-dihydroxybenzene). I had two liters made up, but I didn’t like the looks of it. When I made it up some time ago, it was colorless, indiscernible from water. It now has a very pale tan cast. Upon reflection, I realized that the other two isomers of this chemical, 1,3-dihydroxybenzene (AKA catechol or pyrocatechol) and 1,4-dihydroxybenzene (AKA hydroquinone), are both used in developers for silver halide black-and-white film and paper. As anyone who’s done black-and-white darkroom processing will remember, film and paper developers oxidize and turn brown as they age.

So I did a quick check and found that the Seliwanoff test worked properly with the tannish solution. Still, better safe than sorry, so I disposed of the aging solution and made up fresh.

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