Povidone I2 Recovery via Sublimation

by LabTop


Make or buy a coldfinger (see below), boil your fluid to absolute dryness, without burning the dry restant, then hang your coldfinger in an appropriate Erlenmeyer, and heat gently the now dry restant. Make your coldfinger fat-free with acetone first (on the outside where the I2 will condense). The I2 will sublimate from the solid form into the gas form, without getting a fluid first (that's sublimation), and the gaseous I2 will resublime from the gaseous form into the solid form against the cold wall from the coldfinger. A little bit will of course also resublime against the upper part of the Erlenmeyer, but that you can also scrape off later, when all your 10% I2 hangs on the cold glass walls.


The coldfinger can just be a reflux condenser with cold water running through it. The I2 will condense on the walls of the condenser. It can then be scraped out when it begins to build up.

If you don't have a reflux condenser at hand, you could improvise a so-called coldfinger, by making a big enough hole in a cork or rubber stop, and in that big hole you press a big glass-reagens-tube all the way down, wherein you fit another 2-hole stopper, which you fit with a long L-shaped glass pipe and a short L-shaped glass pipe. Fit plastictubing to both L-shaped glaspipes, and one tube to an aquarium submersible pump, which you place in a bucket with Icecubes/water. The other tube just returns the water to the bucket. Make a tiny little extra hole in the big stopper with a S-shaped glaspipe or plastic tubing, the bend of the S filled with a tiny bit of MeOH to compensate for overpressure, which will nearly not appear, if you keep the bucket full of ice cubes. If suck-back appears, only MeOH will drop in your system, no harm done.

Now you have a perfect condenser for less then 20 US$.

For the more daring ones, you can use a short fat glaspipe, a bit widened at one end, and fix a rubber balloon over that end, and strap that ballloon with one of those nylon straps they use to keep bundles of cables together in automobiles. Now you can frott the empty balloon through your 3 or 5 liter Erlenmeyer mouth opening, fix the rubber stopper, and fill your balloon with ice water from the bucket with that little aquarium pump. Your cooling area is MUCH bigger this way, only test in advance if the rubber will not get attacked by one of your solvents when you use it in another setup then MM's. Acetone is not good for a rubber balloon, more so when it is hot, then you must fall back to the glass reagens tube. But if you look for those wide-mouth glass vessels in household stores, you could even use a 250 ml roundbottom flask as your coldfinger to fit in a BIG cork. Use candle wax then to fix the BIG stopper. Can be easily broken loose after completion of the reaction.