Talk:Calcium oxide

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Contents 1 Dangerous? 2 Questions! 3 Separate Articles? 4 Reversible vs nonreversible 5 Corpse disposal 5.1 ANSWER 6 Sarcophagi 7 Is Calcuim oxide poisonous? 8 Merge? 9 Modern POV 10 Joules/Kilogram in a BTU/lb 11 portable heat source

[edit] Dangerous?

Can this stuff burn the skin?

[edit] Questions!

In what item or substance is Calcium Oxide found?

What natural material is Calcium Oxide found?

Can CaO react with water to produce Ca+2 ion and H2O2? —Preceding unsigned comment added by 68.16.146.41 (talk) 14:46, 28 May 2008 (UTC)

(paste answers on this page) —Preceding unsigned comment added by 71.227.24.97 (talk) 16:51, 8 December 2007 (UTC)

According to these site, the boiling point and melting point in the previous versions are wrong. --Burn 11:00, 21 Feb 2005 (UTC)

[edit] Separate Articles?

There should be separate articles for lime (mineral) and a redirects from quick lime, burnt lime unslaked lime with common applications, and Calcium Oxide, Magnesium Oxide with more Chemistry. Same goes for the hydroxides. Comments please PeterGrecian 14:25, 19 Apr 2005 (UTC)

Yes, can someone with a login please create those redirects? —DIV (128.250.80.15 (talk) 08:11, 7 December 2007 (UTC))

[edit] Reversible vs nonreversible

In the second paragraph, usage of the terms reversible and non-reversible is incorrect. The thermal decomposition of calcium carbonate is a reversible reaction. The temperature of 900 °C is simply the point at which the partial pressure of the CO₂ + CaO ⇋ CaCO3 equilibrium exceeds atmospheric pressure. At room temperature, that equilibrium pressure is less than the partial pressure of CO₂ in air, hence CaO absorbs CO₂ from air at room temperature. A reaction is reversible if a change in conditions makes it go the opposite way. In this case, changing temerpature does that. I am making an edit to this paragraph based upon that. Karlhahn 20:46, 30 September 2006 (UTC)

[edit] Corpse disposal

My knowledge of this stuff is from popular media and goes no firther than hearing about murderers using it to get rid of bodies. I notice someone has added this widely-quoted feature in the article. However, it looks very out of place where it is. Would a chemist care to move/expand/debunk/clean-up that particular statement? --bodnotbod 19:34, 24 October 2005 (UTC)

I agree that it has no place in a chemistry article. I'm going to remove it. 66.215.44.176 05:24, 22 November 2005 (UTC)

That info should still be somewhere, because the uses of slaked lime are one of the reasons ignoramuses like me look it up in the first place. I'll read about it in an old newspaper, novel, war story, and want to find out more. (I actually came here while looking for somewhere to link lime-burning from Fumifugium, Lindisfarne, etc). So although the chemistry sections are extremely important, this article can't be only a chemistry article – unless there's a separate article on slaked lime (which I'd deprecate) for the social, historical, economic, etc, contexts. Comments? JackyR 20:41, 4 April 2006 (UTC)

I too came here after reading about a murder. How exactly does quicklime dispose of bodies? Bastie 10:01, 7 July 2006 (UTC)

I don't think it does: it's just not caustic enough. Cement dust contains a goodly proportion of calcium oxide, and though its bad for the skin and eyes, we don't often hear of builders' flesh dissolving. I would think quicklime would actiually help preserve a body. It seems to me that it would suck water out of the body, then slowly absorb carbon dioxide from the air to a crust of calcium carbonate. Perhaps the idea was to stop the smell of decay from giving away the location of the body, and became confused in popular mythology with actual disposal. Malcolm Farmer 10:13, 7 July 2006 (UTC)

Followup: I had a vague memory and some googling turned this up, which rather supports my "pickling rather than dissolving" theory: : http://europa.eu.int/eur-lex/lex/LexUriServ/LexUriServ.do?uri=CELEX:52005XC0309(02):EN:HTML where we find: Subsequently, the Benedictine Olivetan monks were responsible for rationalising olive growing practices and were the first to pickle olives by using "lye", an alkaline liquid obtained by dissolving one part of quicklime to 4-5 parts of wood ash in water

One form of lime was certainly added to mass graves during WWII, and during WWI it was shovelled over blast areas after the larger chunks of flesh had been removed (but why?). However, I have also heard of a 1940s London murder where someone used the "wrong form of lime" to attempt to conceal a body, and did indeed preserve it. Expert advice required! JackyR | Talk 13:33, 8 July 2006 (UTC)

Possibly wandering off into original research, but a little googling finds:

for the 1940s murder we have Harry Dobkin: http://www.spartacus.schoolnet.co.uk/2WWdobkin.htm

A more famous murder: http://www.familytrail.com/crippen/DrCrippen2.html The remains had not rotted away because they were sprinkled with slaked lime, a chemical which preserves flesh. Apparently the killer had intended to douse the remains with quicklime, which destroys flesh, but he had carelessly applied the wrong chemical.

And: http://www.historylink.org/essays/output.cfm?file_id=7285

And: http://www.forteantimes.com/articles/159_saintspreserved.shtml ...and how the bodies of St Paschal Baylon, St Francis Xavier and St John of the Cross all remained fresh and intact despite being covered in sacks of quicklime for months.

And more. I see a trend here. Quicklime's reputation for destroying bodies seems considerably overrated, and not borne out by experience, even allowing for the selection bias of detected murders. Since quicklime will quickly turn into slaked lime by absorbing water from the corpse (or the damp soil of the grave), I don't believe the excuse that the murderers used the wrong kind of lime. Partial dehydration (from water being absorbed) + high alkalinity = a pickled corpse. At least the smell is kept down, a useful feature for clandestine or bulk body disposal. Malcolm Farmer 10:31, 10 July 2006 (UTC)

As you say, a trend. Wot we need is a forensics expert/book for the unsimplified version.

Btw, the causticity of cement can indeed be a problem for builders. Afraid this is from TV again, but the colleagues of a man who was rescued from a trench full of concrete described irrigating his face and eyes while waiting for the emergency services, due to their concern about the causticity of the concrete. Skin, of course, replaces itself and acquires horny outer layers where necessary, so minor everyday contact for short periods of time witha live body would have a different effect from months of exposure by a dead one.

But like I say, forensics info needed. JackyR | Talk 11:27, 10 July 2006 (UTC)

And here's one I prepared earlier. A workshop in forensic medicine for police, nurses, lawyers, etc: "In one case an amnesty applicant mentioned the use of lime to bury the body. This was used to accelerate decomposition and to take away the odour. " JackyR | Talk 11:45, 10 July 2006 (UTC)

[edit] ANSWER

It doesn't destroy bodies, it dessicates them to greatly slow decomposition. The advantage? Eliminate the odor. For mass graves, this makes the surrounding area livable for survivors. For murderers, it is a gambit to avoid discovery of the body. 198.49.180.40 22:16, 23 March 2007 (UTC)

[edit] Sarcophagi

I just realized the connection between quicklime and the sarcophagus, which was once typically made of limestone. Sarcophagus means 'flesh eater', because supposedly, limestone coffins were known to expedite the decomposition process. Hopefully I'm not making connections when nothing is really there.

See above. The point isn't accelerating decomposition, indeed, it's retarding it. Consider: Mummification is about preservation, not composting. 198.49.180.40 22:21, 23 March 2007 (UTC)

[edit] Is Calcuim oxide poisonous?

I have heard from a couple of sources but I'm not certian that it's poisonous. I just wanted to know because if it is I'm getting it out of my house and away from kids. Douglas Bradford Oliver 23:53, 22 December 2006 (UTC)

[edit] Merge?

Should this article be merged with Lime (mineral)? Seems to cover the same thing - differences being one is a single compound (CaO), while the other may refer to a collection of compounds. I came here from the coconut page, where it says that burning the leaves or something can result in lime - I don't know what kind of lime, is there a purely organic type from plants? WLU 18:11, 31 January 2007 (UTC)

Having just looked at "Lime (mineral)", I think that it should be deleted altogether. Most of what's there is based on incorrect understanding of the term: lime in its strict sense means exclusively calcium oxide. Any vagueness of interpretation should be consigned to the "Lime: disambiguation" page. LinguisticDemographer 22:58, 3 March 2007 (UTC)

I agree that Lime (mineral) needs a lot of work. —DIV (128.250.80.15 (talk) 08:10, 7 December 2007 (UTC))

[edit] Modern POV

I added a bit on current output to show that the Lime industry, although ancient, is also modern. Lime always has been, and continues to be, made in Lime kilns. The latter article does not reflect this, and I propose to re-write it. LinguisticDemographer 23:06, 3 March 2007 (UTC)

[edit] Joules/Kilogram in a BTU/lb

It's trivial to convert Joules/Kilogram into Watts for a rate of reactant, because a Watt is one Joule per second, exactly, by definition. It's an imperial pain in the anus to do it from British Thermal Units or Calories, because that takes a factor other than one. As a bonus, since most of the world is metric, you'll find a more accurate heat of reaction by the law of averajez. 216.234.170.109 10:40, 23 April 2007 (UTC)

Serious no chemist anywhere uses BTU/lb. That number should be expressed in KJ/mol. This should be changed. 128.253.229.12 18:13, 8 May 2007 (UTC)

As a non-chemist, I second that. Please can someone introduce SI units into this article? DuncanHill 23:17, 5 September 2007 (UTC)

[edit] portable heat source

There is a passing mention about lime used as a portable heat source, but no acutal examples given... -- Cimon Avaro; on a pogostick. 20:07, 29 June 2007 (UTC)

One used to be able to get "self-heating" cans of food. These had an outer skin containing quicklime and a sealed pouch of water, and an inner can with the food. To use, a tool (provided with the can) punctured the pouch of water, and the heat from the slaking of the quicklime heated up the food in the inner can. DuncanHill 23:19, 5 September 2007 (UTC)

And we already have an article - Self-heating can. DuncanHill 23:20, 5 September 2007 (UTC)

Also, I think the writer meant MJ not GJ when he discusses the heat evolved from the reaction of 3.1 kg of CaO with water 65.96.204.151 (talk) 16:19, 1 April 2008 (UTC)