Talk:Calcium oxide

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Acid treatment[edit]

I did notice that most people here seem to be more interested in the de-composition of bodies rather than the actual usage of "raw" lime. Calcium oxide is also widely used an acid remover in the treatment of exaust fume in various industries such as producing metals. Most alloys require fluxing and the main fluxing agents all contain fluorides, by injecting quick lime into the resulting exaust stream it neutralises the fluorides and makes the stream safe to expel to atmosphere.

Dangerous?[edit]

Can this stuff burn the skin?

The truth is, there is enough water evaporating from the palms of your hands at any given time (sweaty or not) to activate the chemicals in quicklime. Always wear personal protection equipment when handling chemicals, especially those in a concentrated form such as pure powder.

Quicklime itself will not burn the skin instantly upon contact, as it only reacts with water. So quicklime can be touched and handled with dry hands safely. As it reacts vigorously with water, contact with eyes, mouth, mucuous membranes in the nose or other parts of the respiratory system should be avoided, since the released heat of reaction causes burns and the formed calcium hydroxide can cause harm by its alkalinity. Never touch quicklime with wet hands, never put your hands into a vessel in with lime is slaked with water!Mirkano (talk) 12:35, 3 September 2008 (UTC)

this is not true iv gotten burned by handling dry lime and yes i was not sweating, its cuastic because of it high ph —Preceding unsigned comment added by 74.65.3.30 (talk) 22:48, 18 December 2009 (UTC)

Questions![edit]

The article's picture shows a rock salt structure. Can someone confirm CaO is a mineral with the Face Centered Cubic Structure? 63.85.81.254 (talk) 19:40, 29 August 2013 (UTC)

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)

Separate Articles?[edit]

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))

Reversible vs nonreversible[edit]

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)

I got caught on this and think the confusion is from reversible reactions vs. reversible processes. Reading over it again the whole sentence seems off. I changed it to say that the reaction spontaneously reverses, which I think is more accurate. --ClimberTom (talk) 14:20, 4 May 2010 (UTC)

Corpse disposal[edit]

My knowledge of this stuff is from popular media and goes no further 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)

ANSWER[edit]

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)

´Makes the surrounding area liveable for survivors´? Give me a break. Mass graves - even official ones - are not in the middle of residential areas! There are still issues like ethics and respect for graves. So usually, there is a godly distance to the next habitation. The issue is only partially the stink. If the bodies are left to rot naturally,they will not only stink, but attract animals to dig them up, serve as a breeding ground for flies and maggots and leak decomposition fluids into the ground water. Critically, the decomposing bodies will act as a breeding ground for bacteria/microorganisms causing diseases or releasing pathogenic compounds. As the pathogens would be spread by the flies, scavenging animals or ground water - or other vectors, this is the true danger of mass graves. Quicklime and slaked lime both act as biocides, preventing/reducing the growth of maggots and pathogenic microorganisms. The bodies will still decompose, but in a slower, less dangerous fashion. Mirkano (talk) 13:31, 3 September 2008 (UTC)

On a separate but not unrelated note, the article mentions quicklime being used to reveal fingerprints? I tried to find this information elsewhere on the internet and it's always verbatim, like it started out on one site and has just been copied and pasted all over the place. There is no in-article citation. Can anyone say where this came from? It really doesn't sound right to me and I'd like to remove it if it isn't really true.71.63.15.156 (talk) 19:28, 16 November 2008 (UTC)

WP ought to have a Lime and corpses article to explain all of this. Drutt (talk) 02:58, 23 July 2009 (UTC)

No need for that and in direct contradiction of the first false "answer":

"The floors of the car had been covered with a thick, white powder. It was quicklime. Quicklime is simply unslaked lime or calcium oxide that has been dehydrated. Anyone who has seen cement being mixed knows what occurs when water is poured on lime. The mixture bubbles and steams as the powder combines with the water, generating a large amount of heat.

"Here the lime served a double purpose in the Nazi economy of brutality. The moist flesh coming in contact with the lime is rapidly dehydrated and burned. The occupants of the cars would be literally burned to death before long, the flesh eaten from their bones. Thus, the Jews would 'die in agony', fulfilling the promise Himmler had issued 'in accord with the will of the Fuehrer' in Warsaw, in 1942. Secondly, the lime would prevent decomposing bodies from spreading disease. It was efficient and inexpensive - a perfectly chosen agent for their purposes."

--- From expert Holocaust eyewitness Jan Karski's book "Story of a Secret State", copied from http://www.shalom-shalom-jerusalem.org/jankarski.html 213.222.131.222 (talk) 12:10, 12 August 2009 (UTC)

Dr. Bill Bass (Founder of the Forensic Anthropology Research Center attached to the University of Tennessee, Knoxville) states in his book The Body Farm "Mixed with the reddish-brown clay was a white, powdery material, which Carrol had told Knudsen was lime, dumped over Monty Hudson's body in a misguided effort to speed it's decomposition. (That seems to be a common misconception among murderers. Lime does reduce the odor of decomposition, but it also reduces the rate of decomposition. As a result, a lime-covered body may be less likely to get sniffed out, but it's more likely to linger.)" (not my emphasis.) I would trust his professional expertise, considering he is a renowned forensic anthropologist. You might want to check his Wiki Page, as well, under William B. Bass. Also, to quote the cited Wiki page on Slaked, or Hydrated Lime; "Calcium hydroxide is known to have a strong anti-microbial effect and is a bone-regeneration stimulant.[2]" Though, it can burn or blister skin, since both forms of Lime (this page and Hydrated Lime,) are caustic alkaline chemicals. But as far as forensics is concerned, it works on a corpse as an anti-microbial. Hopefully this clears up some confusion. Munin and hugin (talk) 09:03, 13 December 2009 (UTC)

While everyone is using popular media as a source, I would point out that a white, powdery substance which was probably not cocaine was sprinkled on the corps of Amadeus Motzart at the end of the 1982 film Amadeus. Does anyone have an earlier use of lime documented in popular media? It seems we are unable to exchange information on this substance as it may be useful to murderers, but that may be a bit over-cautious.71.191.247.254 (talk) 22:05, 16 August 2011 (UTC)

Just a note on chemistry and decomposition, I'm sure that the effect of quicklime on dead animal material varies depending on the environmental conditions around lime and corpse. One of the hazards of handling quicklime, and why burned lime is usually slaked unless quicklime is specifically needed, is that the process of slaking quicklime is highly exothermic. So I do not doubt reports of quicklime in mass graves in an environment where rain is going to soak down through the dirt to the pile of quicklime and corpses. Heat and moisture speed decomposition, and the right insulating-value dirt or debris on top would tend to hold in the heat. In a dry environment, I don't doubt that quicklime would slow decomposition by dessicating the corpse--in effect, you should get a somewhat chemical-burned, somewhat mummified corpse if you do this in an arid or semi-arid place OR if whatever you pile on top of the mass grave is insufficiently permeable to water. Enough water over permeable soil cover = trapped heat, fast decomposition. Not enough water = dessicated body. No soil cover to trap the heat, you'd just get rapidly slaked lime and lime-water, which could retard decomposition. So it's not an either-or issue. The function of quicklime in a mass grave (or other bio-degradable organic pit) is to generate and sustain heat over time. Anything about the pit design, contents, or environmental conditions that chemically interferes with that will produce unintended results. It is probably enough to say, "Fictional or historical accounts of quicklime in pits to affect the rate of decomposition of organic matter rely on complex interactions of heat and water and are highly dependent on the specific construction and environmental conditions of the pit and contents." That answers the question, roughly, without exactly providing detailed how-to for serial killers or other murder-minded individuals. It's a polite and chemically accurate version of, "It all depends." -- I'm relying on my own knowledge of chemistry, so you might call this "original research," or you might call it common sense--decomposition is biochemical, and any ONE thing isn't going to have a "magic bullet" effect in the absence of control of other factors. I guess what I'm really suggesting here is phraseology for the obvious (to anyone who remembers high school chemistry and high school biology at all) "it all depends." Okay, that's long, but it's my suggestion. Bluewillow991967 (talk) 20:43, 13 November 2013 (UTC)Bluewillow991967

Sarcophagi[edit]

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)

Yeah - and what is the connection between limestone (calcium carbonate) and quicklime (calcium oxide), duh? Completely different chemical compounds. Limestone is inert. Does not react with flesh, blood or other body fluids - except stomach acid. That limestone eats flesh is a superstition. Mirkano (talk) 13:53, 3 September 2008 (UTC)

Is Calcuim oxide poisonous?[edit]

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)

No, calcium oxide is not poisonous. Exposed to air, it will quickly convert to calcium hydroxide and over time to calcium carbonate. Calcium hydroxide is in every cement, concrete, render, most plasters, some paints, as well as being used in fertilizers and in drinking water treatment, rest assured, that you cannot avoid exposure to it. Mirkano (talk) 13:36, 3 September 2008 (UTC)

yes it is, if you swallow it you will die that a poisin —Preceding unsigned comment added by 74.65.3.30 (talk) 22:47, 20 December 2009 (UTC)

By that logic lava is a poison.

Merge?[edit]

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))

Just wanted to add that it is actually used in cooking process of some kinds of fruit desserts in south Albania and maybe Greece too. —Preceding unsigned comment added by 70.55.218.203 (talk) 03:33, 29 July 2009 (UTC)

Modern POV[edit]

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)

Joules/Kilogram in a BTU/lb[edit]

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)

portable heat source[edit]

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) why is calcium oxde used on fields????? —Preceding unsigned comment added by 86.160.75.129 (talk) 09:35, 12 October 2008 (UTC)

calcium oxide[edit]

the calcium oxide can be use as a preservative? —Preceding unsigned comment added by 121.1.23.210 (talk) 06:30, 18 March 2009 (UTC)

Native lime[edit]

"The name lime (native lime) refers to a very rare mineral of the CaO composition." Any one understand what that is about ? -- Beardo (talk) 20:07, 13 July 2009 (UTC)

After seeing it noted on the calcium hydroxide page that mineral forms of that (portlandite) are rare, I suspect that's what the line is referring to. It's either in the wrong article or makes no sense, so I took it out. KarlM (talk) 07:43, 26 December 2009 (UTC)

CaO when exposed to air goes to Ca(OH)2 then CaCO3[edit]

As noted above, when Calcium Oxide is exposed to air the first thing it does is convert to Calcium Hydroxide. The article indicates that it “immediately” takes on Carbon Dioxide, while technically this may be true, it more immediately takes on humidity from the air and converts to Calcium Hydroxide and then converts to Calcium Carbonate. While this may seem like a nit, I think it is worth discussing more in detail. I produced some Calcium Oxide by heating sea shells to 1100 C, then let the resulting Calcium Oxide sit exposed to air with a relative humidity of 75%. Within a week the volume seemingly doubled, but what did I have? Calcium Hydroxide, or Calcium Carbonate? So I ran an experiment and put 5g of Calcium Oxide on a scale, within 3 days I had exactly 6.6g of power which directly corresponds to the weight of Calcium Hydroxide, not Calcium Carbonate; which would be 8.9g. After the 3 days, the on take of weight seemingly stopped indicating that the absorption of Carbon Dioxide is much slower than the reaction of Calcium Oxide with humidity. Now the interesting question to ask is… Can Calcium Oxide take on Carbon Dioxide in the absence of water/humidity; that is, must it first convert to Calcium Hydroxide before it can take on Carbon Dioxide? If you look at Soda Lime as a Carbon Dioxide Scrubber, it is the Calcium Hydroxide that takes on the Carbon Dioxide (from the Sodium Bicarbonate / Sodium Hydroxide catalyst). If you look at the Calcium Hydroxide page, it implies that Carbon Dioxide is taken on when mixed in water (milk of lime). I am not knowledgeable in these areas, and am therefore looking to those who are for more detail. BTW: Overall, I think these are great articles. KeithRV (talk) 19:56, 27 October 2009 (UTC)

It would be great if you did some research and came up with some published sources that explain this in detail. Note that Wikipedia does not allow original research in articles.—Tetracube (talk) 20:05, 27 October 2009 (UTC)

"Usage" clarification[edit]

Should the uses of hydrated lime be mentioned in this article? The second paragraph begins "It is also used..." suggesting that both the first and second paragraphs discuss the usage of hydrated lime, not quick lime. As a student of this subject I am confused here. Perhaps someone who is knowledgeable could edit the usage section so that it clearly tells what quick lime is used for as compared/contrasted to what hydrated lime is used for. Travis28 (talk) 23:39, 30 July 2010 (UTC)

Lime in Building[edit]

The article states "There is archeological evidence that Pre-Pottery Neolithic B humans used limestone-based plaster for flooring and other uses" Lime mortar of course was used almost exclusively for masonry work until the early twentieth century, and still has advatages over cement mortar. However it was also used extensively for screeded floors, as "limeash" until the introduction of cheap tongue and grooved timber boarding. Rushes would be laid over the timber joists and the limeash applied over as a screed. ref: Wright. A., (1999) "Care and Repair of Old Floors,"Society for the Protection of Ancient Buildings. Chevin (talk)

Solubility[edit]

I find it highly dubious that this compound is soluble in water, 'reactive with water', yes, but not soluble. Someone needs to check this entry in the chembox. Plasmic Physics (talk) 13:01, 13 May 2013 (UTC)

NFPA Diamond[edit]

What is the source for the NFPA diamond? Cfr. http://cameochemicals.noaa.gov/chemical/311 — Preceding unsigned comment added by Ossido (talkcontribs) 01:30, 11 April 2014 (UTC) Also https://ww2.valdosta.edu/~tauyeno/chemicals/Calcium%20oxide.pdf http://www.lhoist.us/pdf/Quicklime042908.pdf http://www.lhoist.us/pdf/lna_msds_quicklime.pdf seem to give all different ratings. — Preceding unsigned comment added by Ossido (talkcontribs) 01:38, 11 April 2014 (UTC)

Color problem with image of atomic structure[edit]

There's a problem with the image. In the limestone article, the calcium atoms are colored green. Here, they are colored white. White is generally reserved for hydrogen. Br77rino (talk) 01:44, 19 June 2014 (UTC)