I have inherited 3L of black ATB (acetylene tetrabromide) that apparently formed when mineral separates were processed without having the hand-magnet fraction removed, i.e., apparently there is a reaction between ATB and magnetite and/or steel from the crushers that renders the solvent black. I have tried washing the black ATB with an aqueous solution of Na-thiosulfate and also Na-dithionite (recommended by a chemist), but this has had no positive effect. Filtering through 2.5µm cone filters does nothing. 10 minutes of low-spin centrifuging does nothing. Running it over activated charcoal does nothing.
I agree: dry it with some insoluble anhydrous salt (like Na2SO4, for instance) and then distill under reduced pressure. The boiling point at 1 atm is about 244ºC for 1,1,2,2-tetrabromoethane.
Dear Mr. Price, i suggest you put it into a freezer. The meting point of the pure material is minus 1.1 °C. Usually the solid material is nearly pure and you only have to decant the brown-black liquid phase. If the cyrstalls are not pure enough you may repeat this several times. Nevertheless the colleagues are right fractionate distillation in vaccuo will give a pure fraction. Unfortunately bromo-compounds turn yellow, organge brown and then black in contact with oxygen (oxidizing agents) or daylight. The colour is the result of several comppounds. Therefor separtion in one step is usually not possible. Well, in most cases crystallization cannot be used because of the low melting point of the halide compounds but in your case it might work.
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