Talk:Calcium carbonate

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Just a thought[edit]

Seems to me most pages dont have this much data in the main article, anyone else feel it should be moved to a data page? —Preceding unsigned comment added by (talk) 02:41, 20 August 2009 (UTC)


Could someone show about the solubility of calcium carbonate in water for vary temperature such as 25 degrees celcius to 100 degrees celcius ?


Could someone put the 3D structure and 2D structure of CaCO3 on the page so as to show the proper bonding.

Dr. Simmons[edit]

Who is Dr Simmons? Thes entinel 03:28, 16 April 2006 (UTC)

There are references on the Internet to research by someone named Simmons using CaCO3 to raise the pH of a natural water resource. So I don't think that's vandalism. It's just written really badly.
On the other hand, the information that the mamalian eye lens is made from CaCO3 just seems wrong. TheGoblin 20:11, 9 May 2006 (UTC)

Solubility of calcium carbonate in water[edit]

The section on water-solubility has some readability issues. Indeed if I didn't already know the chemistry of what is going on in the water/CaCO3/dissolved CO2 equilibrium, I'm not sure I'd be able to follow the development in this section. That the section has lots of equations is good, but they are in sore need of more surrounding text that explains what the equations mean. My apologies to the original author of this section if my criticism seems overly harsh. If that author wishes to discuss this with me, please do so on my user-talk page. Within the next few days I will undertake to improve this section. Stay tuned. Karlhahn 17:33, 4 October 2006 (UTC)

I have published the rewrite, and I hope that I have to some degree achieved the goal I stated above. The old version is will be preserved for a while at User:Karlhahn/KarlsSandbox. Please post any comments or criticism you might have of the changes I've made at my user talk page. Karlhahn 03:48, 11 October 2006 (UTC)
A great help, thanks for this, I'd noticed this needed clarification. I plan to completely revamp this article next year - there's so much more to say on this topic. Thanks, Walkerma 04:15, 11 October 2006 (UTC)

Use of ⇋ versus ↔[edit]

I usually use FireFox, and I just noticed that under IE, the ⇋ [double horizontal arrow; symbol for reversible reaction, in FireFox shows as left arrow over right arrow] character doesn't render correctly. Anyone else notice this? I think I'm going to have to replace usage of ⇋ in this article with ↔.

using the {{unicode}} template fixes the problem on some (but not all) versions of IE. Physchim62 (talk) 14:56, 19 October 2006 (UTC)
You're right. I think the newer IE versions can read the Unicode version just fine. We may need to tell one of the bots to stop converting Unicode! I'd rather we didn't go back to the resonance arrow, my students have such a hard time understanding the difference between reversible reactions and resonance as it is without Wikipedia exacerbating the problem! Walkerma 21:14, 19 October 2006 (UTC)
I just substituted the unicode template for the equilibrium arrow, and it works just fine under IE 6. Karl Hahn (T) (C) 18:33, 26 January 2007 (UTC)


Say someone found a large bag of white powder in a forest with "CALCIUM CARBONATE" written on it what should I would they do with it and what do you think it would be there for...? lol

Mix it with sugar and Sell it at a flea market as a cheap antacid. Why it was there in the first place is probably a pretty interesting story in itself. —Preceding unsigned comment added by (talk) 10:46, 19 September 2007 (UTC)
I think it would be advisable to make sure it really is calcium carbonate before you do anything with it... —Preceding unsigned comment added by (talk) 06:31, 7 February 2008 (UTC)


I noticed that the article for calcium carbonate and ((calcium sulfate)) both have the same picture. Which is which? —Preceding unsigned comment added by (talk) 00:48, 6 March 2008 (UTC)

Calc-sinter versus other forms of calcium carbonate[edit]

This question on the Science RefDesk caused me to look at the following pages, none of which made clear the relationships among Calcium carbonate, Calcite, and Calc-sinter. In particular, this section suggests that there are a number of major forms of calcium carbonate, one of which is calcite but none of which is described as calc-sinter. Is this just a transliteration from the German, and for which an English term is in more common use, or should calc-sinter be listed on this page? --Scray (talk) 03:18, 15 December 2008 (UTC)

According to the chap who runs calc-sinter is the same thing as tufa. DuncanHill (talk) 04:08, 15 December 2008 (UTC)
He referred to A Dictionary of the Names of Minerals, by Albert Huntington Chester, 1896. DuncanHill (talk) 04:30, 15 December 2008 (UTC)

Possible typo in PH section[edit]

Regarding: "(water with a Ca2+ concentration above 120 mg/L or 30 °f is considered very hard)."

I wondered if the author intended "... 120 mg/L at 30 °F..." (replace "or" with "at")

Calcium's effect on seawater's ability to absorb CO2[edit]

I came to this article in search of an answer to a simple question but I couldn't find the answer directly, nor could I understand (with confidence) enough of what is said to deduce an answer. Here is the question. Assume rain dropping on the ocean surface is fully loaded with CO2, driving the rain droplet's pH to 5.7 . Assume there is no Ca in the rain. Let's say seawater has a pH of, to pick a reasonable number, 7.5 . The question is what happens to the load of CO2 in the rain drop when it starts to mix with the surface seawater? Atmospheric CO2 is in equilibrium with the seawater surface water already. So the immediate effect of the rain drop hitting the ocean surface is to dilute the Ca concentration, and to find some intermediate pH as the mixing starts. Does the net effect of everything happening lead to the CO2 being ejected from the (diluted) seawater, returning to the atmosphere? Or is the CO2 captured, and I assume locked up by the Ca as the diluted seawater gets fully mixed and the pH approaches the initial seawater pH? blackcloak (talk) 07:25, 17 January 2009 (UTC)

some questions[edit]

In the Henry's law equation relating the solubility of carbon dioxide in water as a function of its partial pressure, does the concentration of dissolved carbon dioxide in that formula refer to the concentration of molecular carbon dioxide or the total solubility of the gas in water (that is molecular carbon dioxide + undissociated carbonic acid + bicarbonate ions + carbonate ions)?

Likewise, is the solubility product of calcium carbonate to be interpreted as the concentration of doubly charged calcium multiplied by the concentration of doubly charged carbonate ions? If so, how are these calculated from the solubility of calcium carbonate in water, where the calcium ions are also hydrolysed, so some will be present as Ca(OH)+? CO2curious (talk) 10:59, 2 February 2009 (UTC)

"during the past 15 years"[edit]

which years exactly? Rtdrury (talk) 09:55, 19 April 2009 (UTC)

Formula in infobox[edit]

The infobox gives the formula as CCaO3 rather than the more familiar CaCO3. Any idea how to switch the C and Ca? It appears not to be affected by the order of the elements in the template, as it retained this structure when tried switching the order. -- Timberframe (talk) 17:38, 11 January 2010 (UTC)


In the article ”Calcium carbonate” and under subtitle “Solubility” it is stated that the Henry’s constant for CO2 in water is kH = 29,76 atm/(mol/L).

Further down under subtitle ”With varying pH”, an equation for [Ca2+]max is presented, which contains this Henry’s constant, kH.

But, a dimensional analys of that equation [Ca2+]max = (Ksp*[H+]^2)/(Kh*Ka1*Ka2*kH*PCO2) results in that [Ca2+] would have the dimension “1/(atm)^2”. This seems not correct, while dimension “mol/L” would be expected. It is evident that if kH has “atm/(mol/L)” as dimension and PCO2 has “atm”, that “kH*PCO2”, will result in the dimension “(atm^2)/(mol/L), and this could not be correct.

When I based on the equilibrium equations in the article establish the expression for [Ca2+]max I get the kH in the numerator (not in the denominator). Like this: [Ca2+]max = (Ksp*kH*[H+]^2)/(Kh*Ka1*Ka2*PCO2) with dimension [mol/L]

Under subtitle “With varying pH”, under the comments is stated that “Water with a pH maintained to 7 can dissolve up to 15.9 g/L of CaCO3.” This, I get also when using my above suggested equation for [Ca2+]max. Thus, the values for [Ca2+]max in the table seems incorrect.

It seems thus as if the kH by the author has been put in the denominator instead of in the nominator. 18 of april, 2010.

Should this article be expanded, with more detail? ZzzyzxZzzyzx (talk) 05:07, 2 June 2010 (UTC)

It appears that the values in the table in this "With varying pH" subsection were calculated with an incorrect formula that had kh in the denominator instead of in the numerator. The correct values, in units of 0.001 mol/L are 159, 63.5, 25.3, 10.1, 4.00, 1.59, 0.635, 0.470, and 0.253. (The bottom line in units of g/L are those values multiplied by 40.078 g/mol.) Note that the new value for pH=8.27 is now in agreement with the 4.70 x 10^-4 mol/L value given in table in the Solubility section. The new g/L value at pH=7 is 0.159 mol/L*100.087 g/mol = 15.9 g/L rather than 15.9 mg/L as stated in the commentary below the table. I am still not fully comfortable with this section and these corrections so I will not yet making the changes.
It would be nice if both tables used the same Ksp of 4.8 x 10^-9 M as provided in the data box at the top of this article, but that consistency would require a recalculation of these tables each time that data box value was changed. — Preceding unsigned comment added by (talk) 00:49, 12 December 2011 (UTC)

Incorrect informatoin[edit]

This article states that limestone materials are no long used for construction due to acid rain. I live in an area where there is a lot of limestone used in new construction. It is used in retaining walls, fences, building walls, walkways, steps, landings and much more.

The assertion that limestone is no longer used due to acid rain is absolutely wrong.

Oldtexanengineer (talk) 01:06, 17 September 2010 (UTC)

Microbes used to fill building cracks[edit]

Here's a link on a genetically modified microbe that "swims" down small concrete building cracks, producing calcium carbonate and "bacterial glue" as a crack filler ("LiveScience" Nov. 15, 2010):

Great for SF earthquakes. And nice plot for a scifi thriller too!

DonL (talk) 19:28, 17 November 2010 (UTC)

apparent error in preparation section[edit]

The text reads, "Alternatively, calcium carbonate is prepared by calcining crude calcium oxide." According to the formula shown, "CaCO3 → CaO + CO2", this should read: calcium oxide is prepared by calcining calcium carbonate. (talk) 17:03, 5 April 2011 (UTC)

Cleanup on 5. Uses[edit]

Repetitive use of "is also", on a number of five times. —Preceding unsigned comment added by (talk) 01:57, 29 April 2011 (UTC)

Something seems very wrong in the comments on swimming pools[edit]

In the section "With varying pH", the table shows that [Ca2+]max is 1.14 mg/L at a pH of 7.4. Sounds reasonable; 7.4 is more alkaline than 7, so you can dissolve less calcium at 7.4 than 7.0.

First bullet below the table states that water with a pH fixed at 7 can dissolve up to 15.9 mg/L of CaCO3. I don't quite see how to line this up with the value given in the table, which is 7.21 mg/L Ca2+ concentration, but if I worked it through using the molecular weights it would probably be all good.

But then, in the third bullet, it's stated that if the pH is kept at 7.4, which is distinctly more alkaline than the 7.0 level we were just talking about, the maximum Ca2+ concentration is 1010 mg/L. Now, that's more than 50 times the value shown in the table, it's 'way higher than the value just given for pH 7.0 (when it should presumably be lower, not higher, at the more alkaline pH) and I see no clue as to where it came from.

So, am I confused, or is there an error here? (If it's the former I'd appreciate it if someone would elucidate this.) Salaw (talk) 05:22, 4 January 2014 (UTC)

industry for concrete / cement[edit]

Industrial calcium carbonate production is not linked to high-E consumption industry and CO2 pollution ?

I noted no section on industrial scale production in developed world.

cf [1] G. Robert Shiplett 12:18, 9 March 2014 (UTC)

Resolving issues about pH and swimming pool section[edit]

A very useful article. But the current section on solubility “With varying pH” is based on an impossible scenario: pH regulation through bicarbonate and acid addition, while maintaining equilibrium with atmospheric carbon dioxide. This leads to contradictions in the remainder of the section, some of which are raised in talk posts above. One approach to correction might be a careful rewrite of this section under a scenario of pH control using chemicals other than (bi)carbonate; but the practical connection would be obscure (to me). Alternatively, I suggest replacing this section with one that retains the important practical connection to scaling in swimming pools, a good example of systems away from equilibrium with atmospheric carbon dioxide, that easily introduces temperature and salinity as important factors (along with pH and added bicarbonate level) affecting the maximum calcium level before scaling.

R Ge B (talk) 03:31, 18 March 2014 (UTC)