[Strawbale] Carbide Lime

[Murray Hollis]

Rob
Acetylene (C2H2) production from calcium carbide (CaC2) is achieved by
reacting the carbide with water [CaC2 + H20 = C2H2 + CaO], but the CaO will
immediately and violently (exothermic) react with the water to produce
'hydrated' lime {Ca(OH)2}  [CaO + H2O = Ca(OH)2]. As I mentioned in another
communication, the hydrated lime reacts very very slowly with the CO2 in the
air unless the hydrated lime is continuously maintained wet. I suspect that
the reaction is still very slow, but I am not sure about that case.
This acetylene production reaction was the basis of the (very) old carbide
lamps where water was dripped into a chamber containing calcium carbide to
produce the acetylene gas, which was burnt. The sludge that remained after
the carbide was exhausted was calcium hydroxide (hydrated lime). 
Murray

> -----Original Message-----
> From: strawbale-bounces at listserv.repp.org [mailto:strawbale-
> bounces at listserv.repp.org] On Behalf Of Stone Tool
> Sent: Wednesday, April 25, 2007 12:38 PM
> To: strawbale at listserv.repp.org
> Subject: Re: [Strawbale] Carbide Lime
> 
> Rob:
> 	Your advice is excellent...... I should have realized what you said
> without having to be told
> 
> 	The carbide lime is not dry hyrate that requires slaking I think....
> though I'm not sure.   It was calcium carbide most recently, and calcium
> carbide is reacted with water to produce acetylene leaving lime
> behind..... which has already been in contact with water in the previous
> process...... It is at least partially hydrated.  I am not at all sure
> that slaking is a part of the required process.   This carbide lime is
> outdoors in the weather, and exposed to rain and snow, sun and
> wind.......... My question would be to what degree has it already been
> carbonated while living in a heap?   And is it actually useful for
> stucco and plaster without kilning?   If it had been bagged or binned
> after the process it would be a stable and predictable product......
> pushed up into a mountain out doors ?????????  I don't know.
> 
> 	 A small quantity for an experiment is in order methinks!
> 
>                            H.W.