Magpie
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Registered: 1-11-2003
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Mood: Chemistry: the subtle science.
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Recrystallation of Fertilizer Grade Urea
1. Set up a 15cm Buchner funnel with filter paper on a 1000 ml suction flask. A smaller funnel and a 500 ml suction flask would also be suitable.
2. Place the Buchner funnel in an oven set at 100°C.
3. Using a mortar and pestle crush 100g of urea prills.
4. Place 200 ml of denatured alcohol in a 500 or 1000 ml Erlenmeyer flask
5. Cover the mouth of the flask with a small watch glass.
Warning: Boiling the alcohol must be done in a hood or outside as alcohol vapors are extremely flammable.
6. Add a large stir bar and heat the alcohol to a boil on a magnetic stirrer-hotplate.
7. Add the crushed urea. Heat while stirring until the urea is all dissolved, or nearly so. The solution will be clear. See note 1.
8. Place the hot Buchner funnel on the suction flask. Seal the paper to the funnel with a little alcohol.
9. Apply suction to the funnel then pour the hot urea solution through the funnel.
10. Allow the filtrate to cool to room temperature then chill the flask in an ice-bath.
11. Using a wooden dowel work the crystal slush out of the flask into a beaker.
12. Set up the Buchner funnel again. Pour the slush onto the Buchner and remove the entrained alcohol by suction. Press the crystals to expel
alcohol using the bottom of a small beaker.
13. Place the wet crystals on a dinner plate and allow them to air dry overnight.
14. Grind the crystals to a uniform powder using a mortar and pestle.
15. If the crystals still are not dry place in an 80°C oven for 1 hour.
16. My yields were 57% and 59% with only cooling the slush to room temperature. Place the crystals in a sealed container.
Notes:
1. Per forum member not_important do not expose the urea to the hot alcohol any longer than necessary. Both water and alcohols slowly
hydrolyze urea.
2. Also from not_important:
One gram of urea dissolves in
1 gram H2O
10 ml 95% ethanol
1 ml 95% ethanol boiling
20 ml absolute ethanol
6 ml MeOH
[Edited on 13-7-2015 by Magpie]
[Edited on 18-7-2015 by Magpie]
[Edited on 18-7-2015 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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NedsHead
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Thanks Magpie, I bought a 3kg bag of fertilizer grade Urea just last week and was procrastinating about finding a procedure to recristalize. For the
second time this week things I've needed have landed in my lap without any effort at all. I hope this run of luck continues
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Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
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Mood: Chemistry: the subtle science.
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I'm glad it's timely for you NedsHead.
I just recrystallized 200g of urea in preparation for making hydrazine sulfate. It occurred to me that this procedure might well be useful to others.
I have a 50 lb bag of urea I bought for only $10. This will last me a lifetime. Mostly I use it for de-icing my sidewalks in the winter.
The single most important condition for a successful synthesis is good mixing - Nicodem
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NedsHead
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Location: South Australia
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200 down and Just 22,479 grams to go Magpie:) I think I'll buy a filter flask and butcher funnel before I give this a go, I was waiting for a good
excuse to spend the money and now I have one
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