smuv
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Lime woes
Quicklime is one of those chemicals that I imagined would be very easy to find...but not so. I have been to home improvement stores (Lowes and Home
depot for those in the U.S.) and they only carry gardening lime (limestone) and slaked lime. What types of stores sell quicklime (CaO MgO)?
Any help locating lime would be greatly appreciated.
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garage chemist
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The same is true in germany too. No CaO in the stores.
But ceramics suppliers often have it, in 50kg sacks. You could search for a local one. I have also seen online ones that carry it.
If you cant get any CaO, buy the slaked lime, and "re-calcine" it. It already loses its water at 450°C to form CaO again, that temperature can be
easily reached in a steel can on a charcoal fire (cover the can to keep CO2 from the fire out).
[Edited on 11-7-2007 by garage chemist]
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chemkid
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Calcium carbonate (shells, limestone) in a pot on a bed of hot coals or a fire should do it. Release carbon dioxide to form calcium oxide. Add water
for calcium hydroxide.
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not_important
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| Quote: | Originally posted by chemkid
Calcium carbonate (shells, limestone) in a pot on a bed of hot coals or a fire should do it. Release carbon dioxide to form calcium oxide. Add water
for calcium hydroxide. |
You need to get to 900 C or so to do this with any speed. This is a good orange glow, even bright cherry red is under 800 C.
You can speed things up by having some airflow, but that should be drawn from fresh air, not gases coming off the fuel.
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smuv
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yes...calcination is an option... I was just trying to avoid the process. Sometimes making/purifying every single chemical I use just gets tedious.
Thank you for the replies
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chemkid
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900 C would be hard to achieve for extended periodis of time, maybe a little bit of propelent would help, or bellows, or store bought charcoal. But
becuase much of the lime you may find on store shelves may have gone bad (calcium hydroxide), it might be worthwhile to make some calcium oxide
yourself despite thet fact that it is annoying to do. Besides you can use the wood ash to make potasium permangate and if your good you can get the
wood and the shells all for free!
chemkid
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smuv
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Well...I think if I do try it I'd use calcium hydroxide, just because it has a more manageable decomposition temperature (580c according to wiki).
Although more effort would need to be put into protecting the Ca(OH)2 from the charcoal's CO2.
All in all though...I think this would be a lot of work just to obtain a desiccant. If I don't find it locally I am considering just buying a couple
pounds of molecular sieves.
p.s. Garage chemist do you know why CaO is used in pottery?
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chemkid
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common source for calcium hydroxide?
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smuv
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slaked lime
Edit: This is what CaO is being replaced with for masonry uses
[Edited on 14-7-2007 by smuv]
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chemkid
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Do local home depot/ace/lowes carry that?
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smuv
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yes check my edit
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chemkid
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thanks
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