Talk:Acid

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Merger proposal[edit]

I believe Strong acid should be merged into Acid. Not only does it make logical sense, as strong acids are a sub-category of acids, but it matches the format taken by bases and strong bases (strong base is a section of Base). If the consensus is that they should not be merged, I suggest moving strong base to its own article. Neonfuzz (talk) 18:37, 27 September 2011 (UTC)

One problem is that this Acid article is already very long (41K). Instead I would suggest merging the three articles Strong acid (7K), Weak acid (7.5K) and Superacid (5.6K) into one new article on Acid strength, initially with three sections. And yes, for consistency we could also merge the strong base section of Base (13K) with Weak base (7.5K) and Superbase (5K) into one new article on Base strength. Dirac66 (talk) 22:31, 27 September 2011 (UTC)
This is a great idea! I can probably get to work on it within the next few weeks. Neonfuzz (talk) 15:37, 29 September 2011 (UTC)
Agreed! Having separate (much smaller) articles makes less sense than one longer article, as readers will gain more insight into the context rather than as a stand-alone topic.--Gilderien Talk|Contribs 20:08, 17 October 2011 (UTC)

I definitely think this is a good idea, but who is going to do it? I'm not sure how, and I don't want to attampt for fear of doing something wrong. I don't see why anyone hasn't done this, yet. — Preceding unsigned comment added by W192 (talkcontribs) 18:28, 27 December 2011 (UTC)

OK, thanks for the reminder. It is complicated to decide what to do exactly, but I have now started. First I created a new article Acid strength by copy-pasting the former Acid strength section of this Acid article, and deleted its subsections from this new article. Then I copy-pasted the entire content of the former Strong acid article into Acid strength, and replaced Strong acid by a redirect. For these two actions I consider that adequate notice was given, since the Merger proposal was on both the Acid and Strong acid article for several months.
Next proposed step is to copy-paste the contents of Weak acid and Superacid into Acid strength. However since the merger proposal was not previously on these two articles, I will post one now and wait 14 days for comments before proceeding. And after the acid merger is finished, I will think about bases.
And finally I will copy this discussion to Talk:Acid strength which seems the best place for further discussion. Dirac66 (talk) 03:09, 2 January 2012 (UTC)

Keep superacid separate. They are pretty particular, peculiar compounds with certain geometry and element. Leave an article that covers them and then have acid strength be about the whole concept of strength. Super acid is not just "very strong acids" but more of a class of compounds. I'm fine if you merge weak and strong into acid strength.TCO (talk) 02:58, 1 February 2012 (UTC)

Yes, we did in fact decide at Talk:Acid strength to leave Superacid as a separate article, and to merge Strong acid and Weak acid into Acid strength. The merger has already been done, and I am glad you agree with the decision. Dirac66 (talk) 03:17, 1 February 2012 (UTC)

Cool! It was confusing with all the different locations of move discussions. Good luck. these are key articles with huge readership. Go GA?TCO (talk) 03:27, 1 February 2012 (UTC)

Vinylogous subsection errors[edit]

The subsection Vinylogous carboxylic acids contains two serious errors.

  1. It is not true the proton donor is a carbon atom. A vinylogous carboxylic acid has a structure O=C-C=C-O-H. with an O-H proton donor joined to an O=C electron withdrawing group by a C=C ("vinyl" although at least one H is missing). Ascorbic acid for example is an oxygen acid and not a carbon acid - see the structures of acid and conjugate base at Ascorbic acid#Acidity.
  2. The other example is Meldrum's acid which is a carbon acid, but it is not a vinylogous acid as it has no C=C double bond.

Possible fixes:

  1. Delete the incorrect statements and leave just the one example of ascorbic acid without comment.
  2. Change the subsection title to something like Organic acids without a -COOH group, with several types. A good source would be an article by Perez and Perez (J. Chem. Educ. 77, 910 (2000)), who discuss three types of organic acids without -COOH which are strong enough that some molecules were first named acids before their correct structure was known - a) phenols and similar, b) vinylogous carboxylic acids (including ascorbic), and c) carbon acids (including Meldrum's).
  3. Delete the subsection entirely as none of these are really Common acids, which is the section of which this is a subsection. And perhaps put the above list to the article on Organic acids.

Comments? Dirac66 (talk) 22:21, 3 June 2012 (UTC)

Dirac66 is completely correct. I took fix #1. Eugene Kwan (talk) 19:24, 4 June 2012 (UTC)

Diluting acids (might not be helpful, though)[edit]

There is no mention about dilution of acids. I failed to find any other article discussing on it. We have sections for neutralization and acid strengths, but not for this. Shall the dilution of acid, its precaution, exceptions to HF etc. be included (To make this article complete)? Vanischenu mTalk 11:53, 19 July 2012 (UTC)

A s:olid used in baking[edit]

and tartaric acid (a solid used in baking).

That would be a component of baking powder, not just "baking" — Preceding unsigned comment added by 64.229.143.161 (talk) 22:29, 23 October 2015 (UTC)

Yes, "baking powder" would be more accurate than "baking". However another point is that baking powders contain not tartaric acid but rather its monopotassium salt, potassium bitartrate. If this were corrected, the example would be probably too complex to mention in the intro, so I suggest removing tartaric acid from the intro. It would still remain in the list of Carboxylic acids in the last section. Dirac66 (talk) 02:14, 24 October 2015 (UTC)
I have now replaced this example with citric acid (found in citrus fruits) which is a more straightforward example. (At least since we are not discussing structure at this point). Dirac66 (talk) 17:36, 1 May 2016 (UTC)

Edit request[edit]

The list of references tag should be at the very top of the page, above the hatnotes. Please fix that; it is getting on my nerves. Not a creative person (talk) 12:27, 2 February 2016 (UTC)

Lead rewrite[edit]

I tagged the article with "Lead rewrite" . First the lead says an acid "are characterized by a sour taste, the ability to turn blue litmus red,", and then it says there are "three common definitions for acids: the Arrhenius definition, the Brønsted-Lowry definition, and the Lewis definition.". But Lewis acids are not characterized by sour taste etc. Maybe adding something about "normal" acids (the way the words is used by most people), and then add Lewis acids as a side note. Christian75 (talk) 05:08, 29 February 2016 (UTC)

The edit today by Klaus Schmidt-Rohr clarifies the three definitions and improves the article considerably. However the very first paragraph was left unchanged, so we are still telling readers at the outset that acids are sour and turn litmus paper red. I suggest a more modern intro organized as follows:
  1. Paragraph 1. Arrhenius and Bronsted: Acids are proton donors. Considered most typical type.
  2. Paragraph 2. Since H+ is an electron-pair acceptor, Lewis generalized to include other electron-pair acceptors.
  3. Paragraph 3. Historically acids defined by properties = sour, litmus paper, etc. However Modern definitions are concerned with the fundamental chemical reactions common to all acids. (copy-pasted from section Definitions and concepts.)
  4. Note 4: Readers advised not to verify acidity of compounds by tasting :-)) Dirac66 (talk) 15:00, 1 May 2016 (UTC)
I have a strong suspicion that the references to sour taste or litmus are part of some school curriculum that someone feels like must be added for the kids. None of these are fundamental properties of acids, but incidental results of their properties; litmus in particular is pretty bad since it's a purpose-concocted mixture of dyes. These are also unsourced. Furthermore, I think there should be a better and more concise way to write a definition of an acid instead of going into historical and definitional discussions in the lead. There's the hangup with aqueous solutions and pH, for example, even though acids exist in all sorts of solvents, sometimes these are better than water. For example:
An acid is chemical compound that accepts electron pairs either directly or by releasing protons (H+) into the solution, which then accept electron pairs. (ref IUPAC Gold Book) Acids react with bases by accepting an electron pair from them and form salts or complexes with them. Brönsted acids (HX) have a hydrogen atom that easily loses its electron, dissociating the molecule into a counterion (X-) and a hydrogen ion (H+), which is an electron pair acceptor. A common example is hydrogen chloride, which dissociates into H+ and Cl- ions. In water solutions, protons are solvated as hydronium ions (H3O+). Lewis acids are acids that do not release protons but accept electrons directly. Boron trifluoride (BF3) is an example of a Lewis acid that is not a Brönsted acid; it reacts with dimethyl sulfide (Me2S) by forming a Me2S-BF3 complex where the Lewis base Me2S donates an electron pair to BF3.
Brönsted acids taste sour and give water solutions with a high proton activity, i.e. a pH below 7. Acidity can be detected with an acid-base indicator such as litmus paper, which turns red, or with a ion-selective electrode (pH meter). Acidity may be defined for any proton in a molecule; therefore, for example water or alcohol are considered acids in superbasic solutions. Conventionally, "acids" refer to substances that are significantly more acidic than water. Acids exist because the counterion is stable and non-basic. The acidity of a substance is equivalent to the inverse of the basicity of the counterion. Therefore, there are strong acids and weak acids. Strong acids completely dissociate, while weak acids dissociate only partially, as their counterion is still appreciably basic. A common weak acid is ethanoic acid (acetic acid), found in vinegar. It dissociates into hydrogen and acetate ions, but the acetate ion (MeCO2-) is basic, and thus only ca. 1% of acetic acid is in dissociated form.
Explanations about uses of acids, catalysis by acids, hazards of acids
--vuo (talk) 23:10, 24 May 2016 (UTC)
Yes, I agree that this would be much better than the current version. Dirac66 (talk) 23:46, 24 May 2016 (UTC)
I have now rewritten the intro starting from the IUPAC definition as suggested by Vuo. The second paragraph defines Arrhenius as a special case of Brønsted which is the modern view. The properties (sour taste etc. etc.) are in the third paragraph so that it is clear that they are no longer (this is 2016!) the definition of an acid. And the final paragraph of the intro refers to Lewis acids, where I have included Klaus Schmidt-Rohr's point (below) that the word acid implicitly means a Brønsted and not a Lewis acid. Dirac66 (talk) 01:19, 24 June 2016 (UTC)

No lead rewrite needed[edit]

The very first paragraph describes quite correctly what "an acid" is. I have added a sentence (at the end of the second paragraph) that points out that "an acid" will not refer to a Lewis acid, since chemists refer to a Lewis acid as "a Lewis acid", while "an acid" is implicitly an Arrhenius or Brønsted-Lowry acid. So the lead section of this article (which, by the way, is mostly not my work) does not need to be rewritten in a major way. The "warning" tag with the exclamation point at the top of the page should be removed.

[It may seem surprising that "a Lewis acid" is usually not considered "an acid". But this situation is not so unusual for compound words. For instance, “a gun” hardly ever refers to “a heat gun”; the standard definition of “brush” does not include “air brush”; and “a crosswalk” is not included in the definition of “a walk”. And consider an even more extreme example: A "dwarf planet" is never a planet, according to many sources, including Wikipedia: "A dwarf planet is a planetary-mass object that is neither a planet nor a natural satellite." ] Klaus Schmidt-Rohr (talk) 16:45, 23 May 2016 (UTC)

I think you're missing the point. The lead is not the "Definition" section. The current version rambles about different definitions and characteristics without capturing much of the essentials of the article below. Ideally, a lede should be a "mini-article". --vuo (talk) 08:40, 20 June 2016 (UTC)