Fusarium redolens

Acid dissociation constant

Nominator(s): Petergans (talk)

• Featured article candidates/Acid dissociation constant/archive1
• Featured article candidates/Acid dissociation constant/archive2

The concept acid dissociation constant is of major importance in chemistry, physics, earth sciences (including environmental sciences) and biology (including human biology) and is also important in other areas such as the development of new pharmaceuticals and all sorts of industrial processes where acidity has to be controlled. The article presents a comprehensive coverage of the topic and indicates the main areas of application. It should therefore be of interest to a wide range of the readership.

The topic is covered, at an elementary level, in all text-books on general chemistry, though the treatment is usually simplified. The simplifications are explained in this article.

I have been active in research in this subject area since 1972. Our programs Hyperquad are the world market leaders for the determination of acid dissociation constants and stability constants of metal complexes with ligand acids. Correspondence with users of this software has given me an appreciation of the range of applications of interest in research today. This is reflected in the structure of the article.

I am confident that if this article is accepted for featured status that it will enhance the reputation of Wikipedia among scientists and science students.

Petergans (talk) 09:21, 9 October 2008 (UTC)

Comments

• What makes the following reliable sources?
  • http://www.chem.wisc.edu/areas/organic/index-chem.htm (Also this ref is missing an author, publisher and last access date)

This is a source of data, not of the article content. I believe the data to have been reliably taken from the literature. Petergans (talk) 15:39, 9 October 2008 (UTC)

I"m not sure what exactly you mean by "source of data, not of the article content", do you mean that it's not used as a source? If it's not used as a source, why is it in a footnote? If it's being used as a source for data in the article, then it needs to be reliable. Ealdgyth - Talk 16:21, 9 October 2008 (UTC)

Sorry I did not make myself clear. It is an comprehensive source of numerical data, that is, numerical values of acid dissociation constants, the title entity of this article. As such, I prefer to reference it directly in the relevant place in the article rather than list it in external links, but I'll move the reference there if Wiki style demands it.

Regarding reliability, http://www.chem.wisc.edu/areas/reich/pkatable/index.htm gives access to a list of the 64 references to the primary literature from which the data were extracted; the current link is more general and has a link to that page. Petergans (talk) 08:56, 10 October 2008 (UTC)

• Current ref 43 (Washburn) needs to have the link title formatted so it's not a bare url.
  • Done Petergans (talk) 16:08, 9 October 2008 (UTC)

Otherwise, sources look okay, links checked out with the link checker tool. Ealdgyth - Talk 14:06, 9 October 2008 (UTC)

Currently Leaning Oppose I really appreciate the editors/nominator of this article for working on this article and bringing it up to to its current quality. I see that it has been the recipient of nontrivial amounts of thought and elbow grease... I'm seeing two things that concern me: first, the article is a bit beyond the reach of the uninformed reader [insert arguments <here> that uninformed readers won't be examining this article anyhow]. In the first sentence of the WP:LEAD there are already blue links that lead to other articles; I'd have to read those before I could continue on with this one. A WP:LEAD is supposed to function as a stand-alone intro/summary of the article... The article, especially the lead, needs to make an attempt to address a more elementary-level reader.. although it's fine to retain info that is beyond that level in later sections. Second, I'm really not getting a concrete feel of the reasons for its importance. After searching about 3 or 4 minutes I found this book (just the first interesting one I ran across): "Risk Assessment of Chemicals" By C. J. van Leeuwen, Joop L. M. Hermens.. it says "To neglect the chemicals' dissociation may lead to serious misjudgment of their hazard.. " on p. 254. Now that's a real-world fact I can hang onto. I'd like to see more such. Ling.Nut ^{(talk—WP:3IAR)} 10:15, 10 October 2008 (UTC)

The first line of the lead reads "An acid dissociation constant (aka acidity constant, acid-ionization constant) is an equilibrium constant for the dissociation of an acid". If the reader does not already have some grasp of the linked concepts, then I suspect the article will be completely unintelligible to him/her. The links put these concepts on a more rigorous basis. The need to address a more elementary-level reader is a recurrent theme for technical articles like this one and it is difficult to resolve. We have pitched the intro level towards a school student studying chemistry and coming across this idea for the first time.

I take the point about risk assessment and will insert something about it in the importance section. Petergans (talk) 14:45, 10 October 2008 (UTC)

• Please have a look at this link which suggests possible wikilinks for the article. Note that some terms may already have been wikilinked previously in the article, and also that any new wikilinks should typically be double-checked to make sure they are relevant to the article (though for specialized, technical terms it is far less likely that the suggested link is irrelevant. Choose carefully; no real reason you have to add any of the suggested links if they don't appear to add value to the article.
• "Biochemistry Primer for Exercise Science" by Michael E. Houston (p. 5) states: "The stronger the acid (HA), the more it is dissociated, and the higher the concentration of the conjugate base (A-). Therefore, the larger the numerical value for K_a, the stronger the acid." That last sentence in particular is crystal clear. Our article says (what I believe is) the same thing in a different manner: the larger the value of pK_a, the weaker the acid .. but this article is explicitly about K_a. I understand the easy relationship etc. (very roughly, of course), but I think we should couch our explanations in terms of the explicit topic of the article... Ling.Nut ^{(talk—WP:3IAR)} 17:53, 10 October 2008 (UTC)

There is a problem here: in common usage the terms "pK_a" and "acid dissociation constant" are used (wrongly!) almost interchangably. I think that we would have to say something along the lines of - the stronger the acid the larger the values of K_a and the smaller the value of pK_a - but to me this sounds a bit confusing. In practice pK_a values are used much more often than K_a values, but I don't see how this can be reflected in the article title. Petergans (talk) 18:45, 10 October 2008 (UTC)

• Houston (see above) states in his Glossary (p. 245) that 'K_a "describes the ability of an acid to donate a proton". This is a restatement of the observation (above) to the effect that "larger 'K_a = stronger acid", since an acid is apparently a compound that can donate a proton. I can see why you would skip this, since we are unpacking the defition of "acid" here. But really, I think we actually can unpack these things, at least in the lead, without any damage to the article as a whole. I hope you'll understand that my intention is not to dumb-down the article; just to make the WP:LEAD a bit more stand-alone. I understand your stance that the reader must have "some grasp of the linked concepts" (to quote, not to scare-quote). But... the higher the number of elegantly-expressed ideas (some appearing as blue wikilinks) in the lead, the less stand-alone the lead is... thanks Ling.Nut ^{(talk—WP:3IAR)} 18:14, 10 October 2008 (UTC)

These are very helpful comments, thank you very much. I shall be away for the next two weeks so I will get round to dealing with them and others that will come in when I return. Petergans (talk) 18:45, 10 October 2008 (UTC)

Nominators are expected to address issues promptly; if you can't get to this for several weeks, I suggest withdrawal. Also, there are numerous WP:ACCESS issues. SandyGeorgia (Talk) 22:21, 10 October 2008 (UTC)

As a Chemistry Education major, though not an expert by any means (precipitates is one of my weaker areas), all the major problems I see can be summarized into three arguments:

• The article addresses Ka in theory but lacks information of it in practice (i.e. experimental determinations of Ka, notable historic milestones and contributors, and applications to industry). Even the "Importance of pKa values" section which addresses applications to industry remains vague as to specific examples of its usage (i.e. stating that acid disassociation values are used to increase blood absorption of pharmaceuticals but fails to detail an example of a drug that has been adjusted due to this...yes I know that their are copyrights on new drugs but maybe an old one like Aspirin pills).
• The article does not use the simplest and most artful language to communicate ideas. An example of this would be my explanation (above) of what the "example" in the "pharmacology" section was trying to say (which I believe would suffice).
• It does an insufficient job of explaining to the most likely readers of the subject (high school and college students trying to pass Chemisty class) how the equations actually work. It gives the equations and expects the reader to understand how they work. Several examples of real Ka problems (with explanations) would be most effective in breeding understanding of the subject matter.--JEF (talk) 00:41, 11 October 2008 (UTC)