Sciencemadness Discussion Board

Cold finger - how it works

Arthur Dent - 19-2-2011 at 06:00

I read with interest the threads on iodine sublimation and how easier it is when you use a "cold finger" apparatus to condense the purified iodine. In the near future, I will attempt to reclaim some elemental iodine from a batch of sodium iodide I have.

So I was at my favorite surplus store and spotted this lovely thing...



it's a nice cold finger, but i'm not sure how to secure it to the vessel I will use for the sublimation. It has a thin 1 cm-wide glass flange and that's it!

Anyone knows how to secure such a fitting to a vessel? I selected a large 2 cm x 15 cm pyrex test tube as the sublimation vessel. I was thinking of boring an extra big hole in a rubber stopper, but that can't be right?

Or is this setup incomplete and there's an actual piece of glassware that goes along with this cold finger?

Robert


hissingnoise - 19-2-2011 at 09:01

A GG tapered flange would be more convenient for insertion into flasks!
A disk of soft rubber sheet, 2 or 3mm thick with a hole cut in it might be better than a bung . . .