Sciencemadness Discussion Board

dehydrating potassium fluoride

andre178 - 15-12-2009 at 11:39

Hi, I have a large stock of potassium fluoride dihydrate, but I need KF anyhydrous, is there any way of achieving this?

I have access to a lyophilizer (free drying).

Thank you

JohnWW - 16-12-2009 at 06:34

What are you going to use the stuff for? Electrolysis of the molten anhydrous salt to obtain K metal (keep the cathode under argon) and F2 gas?

not_important - 16-12-2009 at 18:42

From A comprehensive treatise on inorganic and theoretical chemistry, Volume 2
By Joseph William Mellor
Quote:
If the soln. of the potassium salt be evaporated above 40°, anhydrous cubic crystals, KF, are obtained, but below this temp., long prismatic crystals of the dihydrate oi potassium fluoride, KF.2H..O. The hydrate is also obtained by evaporating a soln. of potassium fluoride in vacuo ; or by precipitation from the aq. soln. by the addition of alcohol.7 At temp, below 20°, a tetrahydrate of potassium fluoride, KF.4H20, melting at 19'3°, is formed.
...
When pure and dry, potassium fluoride can be kept in glass vessels, but if moisture be present, the glass is etched. Soln. of the fluoride also etch glass and porcelain, and some silica is dissolved.



andre178 - 17-12-2009 at 09:54

thank you for looking up the information, that's been really helpful, I've ended up spinning a whole batch in the rotovap and then storing it in plastic tubes, I went by intuition.
I was thinking of precipitating with alcohol but.... I'll go with the "keep it simple --" approach lol

A