Talk:Calcium oxide

message: 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)
thread_title: Dangerous?

message: 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)
thread_title: Questions!

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

message: 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 ⇋ CaCO</sub>3</sub> 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)
replies: text: 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)
thread_title: Reversible vs nonreversible

message: 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)
thread_title:  Sarcophagi 

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

message: 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)
thread_title: Modern POV

message: 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)
replies: text: As a non-chemist, I second that. Please can someone introduce SI units into this article? DuncanHill 23:17, 5 September 2007 (UTC)
thread_title:  Joules/Kilogram in a BTU/lb 

message: 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)
replies: text: 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)
replies: text: And we already have an article - Self-heating can. DuncanHill 23:20, 5 September 2007 (UTC)
thread_title:  portable heat source 

message: 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)
thread_title:  calcium oxide 

message: "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)
replies: text: 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)
thread_title:  Native lime 

message: 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)
replies: text: 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)
thread_title:  CaO when exposed to air goes to Ca(OH)2 then CaCO3 

message: 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)
thread_title:  "Usage" clarification  

message: 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)
thread_title:  Solubility 

message: What is the source for the NFPA diamond?
Cfr. http://cameochemicals.noaa.gov/chemical/311  — Preceding unsigned comment added by Ossido (talk • contribs) 01:30, 11 April 2014 (UTC)
thread_title:  NFPA Diamond 

message: 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)
thread_title:  Color problem with image of atomic structure 

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thread_title:  External links modified 

message: "...inorganic materials, in which carbonates, oxides and hydroxides of calcium, silicon, magnesium, aluminium, and iron predominate..."
Chemistry is not my strong suit, but aren't all carbonates by definition organic? - SummerPhDv2.0 03:49, 31 March 2018 (UTC)
replies: text: @SummerPhDv2.0 Sorry for this late reply, what about CaCO3, BaCO3, are they organic? -Lemonaka‎ 20:53, 15 December 2023 (UTC)
thread_title:  inorganic carbonate? 

message: Calcium oxide (cao) csn also be used in diet with curd .
It helps in the developing od bone .
Do not let come rashesh in old age . also help in the neurishment of skin in our body 2409:408A:E0A:2E95:0:0:B349:6203 (talk) 03:53, 17 March 2024 (UTC)
thread_title:  Use for body refreshment