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The Hive => Chemistry Discourse => Topic started by: Azarius on April 14, 2002, 07:00:00 PM

Title: powdered KOH dehydration
Post by: Azarius on April 14, 2002, 07:00:00 PM

Can powdered KOH bee dehydrated to remove the atmospheric water it picked up while being powdered simply by heating in an oven @175C, or would this drastically increase K2CO3 content?

Many thanks,
Azarius

Title: It's posible to dehydrate KOH in an owen (dont' ...
Post by: hest on April 14, 2002, 07:14:00 PM

It's posible to dehydrate KOH in an owen (dont' let it melt)
It will pick some CO2 up from the air, but not that much (there is only 200-300ppm to take)

Title: KOH Hydrates
Post by: Elementary on April 14, 2002, 07:25:00 PM

KOH.(H₂O)x

x=4 MP -32.7°C
x=2 MP 35.5°C
x=1.5 and 1 MP 143°C

(Pickering, J.C.S., 1893, 63, 890)

At about 200°C I can't really see much more than small amounts of Carbonate forming.

If you are really bothered by small amounts of carbonate, heat the KOH in an inert atmosphere/vacuum, or heat the KOH higher than 1000°C to rid the CO2

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Nobodys home

Title: But why?
Post by: terbium on April 14, 2002, 08:08:00 PM

Can powdered KOH bee dehydrated to remove the atmospheric water it picked up while being powdered
But if the powdered KOH is being used to isomerize an allylbenzene then is this necessary?

Title: necessity of drying
Post by: Aurelius on April 14, 2002, 11:00:00 PM

Terbium, aurelius wasn't sure if that was retorical.  So... no, it doesn't need to be dried.  it is preferred that no visible water is present, but the minute traces make almost no difference in the course/yeild of the isomerization.  (from practical experience)

Title: k, thanx ppl :)
Post by: Azarius on April 15, 2002, 01:47:00 AM

k, thanx ppl :)