Talk:Phosphoric acid

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Other interesting information could be: Phosphoric acid producers, such as Thermphos International B.V. (www.thermphos.com)

And about Phosphate esters, these are not made from H3PO4 but from P2O5 (Phosphorus pentoxide), PPA (Polyphosphoric acid: highly concentrated phosphoric acid) or POCl3 (Phosphorus oxychloride). I wouldn't mention them here.

Else: there are several ways to produce phosphoric acid, from Wet acid (green acid) that is obtained through the sulphur process described here, but also through a Thermal process, that produces very pure phosphoric acid through the reaction of Water with elemental phosphorus (Yellow phosphorus).

- MahRain. 14 november 2005.

IMHO this article is a real mess:

1. It barely touches on the actual subject of phosphoric acids (of which there are an infinite number in a very rich structural system, but 3 important ones, ortho-, meta- and pyro-);

Offline, I've started writing a separate article about these other phosphoric acid forms. It's currently on the temporary page User:H Padleckas/Temp (Phosphoric acids and Phosphates) H Padleckas 17:58, 14 May 2005 (UTC) H Padleckas 09:00, 19 Jun 2005 (UTC)
Finally, I've finished the main illustration for this article and I've moved the temp page to regular article status; see Phosphoric acids and Phosphates. This article remains about orthophosphoric acid. I've added an note to this effect in the introductory section of this article. H Padleckas 08:45, 24 October 2005 (UTC)
In addition to the article being about orthophosphoric acid, I' ve expanded the article to briefly discuss phosphoric acid as a chemical/reagent and mention the orthophosphoric can be heated to dehydrate it into metaphosphoric acid. Pyrophosphoric acid is currently not mentioned in this article, but there is a link to Phosphoric acids and Phosphates where pyrophosphoric acid is mentioned. H Padleckas 15:28, 24 June 2006 (UTC)

2. Yet it lurches off to discuss irrelevancies like eutrophication from phosphate detergents (this isn't the phosphate article!) while missing all but one or two of the many uses for this important material;

3. It introduces a lot of dubious material which will need fact checking (local anaesthetic?! colour me very skeptical);

4. It is totally disorganised (section "Chemical properties" contains no chemical properties, section "Preparation of phosphoric acid" contains 11 words on one method of preparation while the whole rest of the section is totally unrelated, etc). I suggest hydrochloric acid might make a good template;

I' ve expanded am expanding the article to add more on chemistry of orthophosphoric acid. H Padleckas 15:28, 24 June 2006 (UTC) H Padleckas 20:21, 25 June 2006 (UTC)

5. The section "Processed food use" is at best POV (agro-industrial chemical ?!? They don't use fertiliser grade acid in colas!) and probably just wrong (citric acid ... obtainable from lemons and limes--sorry, nope, it's an agro-industrial chemical made by the Aspergillus niger mould fermenting scrap molasses and waste starch hydrolysates, and it works best if you add some ... phosphoric acid!);

6. The section "Effects on bone calcium" seems very suspicious. In particular, the claim When an excess of phosphorus (through phosphoric acid, for example) is introduced, the body's chemical balance mechanisms will attempt to maintain the proper calcium-phosphorus ionic ratio by extracting calcium from the bones is exactly the opposite of what would be expected from Le Chatelier's principle and not what is expected for normal homeostasis, but hey, biology is a funny thing, if someone comes up with a reputable cite I'll believe it. If not, I'll remove it. I'm foreshadowing all this here because I have a really long backlog and it might be a while before I get to it. Anyone else, please jump in first if you can. -- Securiger 11:21, 28 Mar 2005 (UTC)

I agree with at least items 1 and 4 above. I have previously noticed this article was "wanting" in the chemistry areas and I was hoping to improve it as I got a chance. I'm the person who originally wrote the chemistry section of Hydrochloric acid and the mono-, di-, and tri-, etc. protic acid subsection in the article Acid. I was hoping someday to expand on the chemistry aspects of phosphoric acid in this article, but things take time. H Padleckas 19:09, 28 Mar 2005 (UTC)
Physchim62 had added a Table of Properties for Orthophosphoric acid, which is good. The chemical structure pic is enlarged from the original to fit the table template and has become somewhat fuzzy. Is there any way to reduce this pic size to the original 118x118 pixel size? I would still like to write a Chemistry section at the beginnining of the article, but Physchim62 may beat me to it. I will have to coordinate with him.
H Padleckas 08:45, 24 October 2005 (UTC)
Finally, I' ve expanded am expanding the article to add more on chemistry of orthophosphoric acid. H Padleckas 15:28, 24 June 2006 (UTC) H Padleckas 20:21, 25 June 2006 (UTC)

I just deleted the detergent stuff. Phosphoric acid is not phosphate and it is not used in detergent.

I completely agree with the above- this desperately needs a lot of chemistry added, though currently I'm buried in other work. Walkerma 09:15, 14 May 2005 (UTC)
Looks like you're making good progress on your temp page, Henry. A couple of suggestions- (a) Don't forget the biochemical importance of the conjugate bases- there is a whole page on pyrophosphate, and if you search on "triphosphate" you find a lot of pages containing the word. (b) Could I suggest that phosphate esters DO belong on the page, but phosphite esters are at a different oxidation state and should be considered separately IMHO. I will be writing a page on phosphite esters later in the summer, with a view to writing up the Horner-Wadsworth-Emmons reaction that uses them. Keep up the good work, Walkerma 02:19, 20 Jun 2005 (UTC)
As mentioned above, I moved this temp page contents to the regular article page Phosphoric acids and Phosphates. I'm sorry about the delay, but it took me a while to make the main illustration for it. See Talk:Phosphoric acids and Phosphates for responses to suggestions a) and b) above. H Padleckas 08:45, 24 October 2005 (UTC)

Contents

[edit] June 24 edits made by 152,163.100.66

The edits made by 152,163.100.66 on June 24, 2006 were actually made by me, H Padleckas. It appeared to me as if I was logged on, which is how I usually make my edits, but somehow only the IP address is listed in the contributions history. 152.163.100.130 14:46, 24 June 2006 (UTC) H Padleckas 15:10, 24 June 2006 (UTC)

[edit] Anesthetic?

The article currently claims that phosphoric acid is used as an anesthetic. Can anyone confirm or deny this?

Sounds suspicious to me, but then as said above, bio can be a funny thing. Walkerma 09:15, 14 May 2005 (UTC)

Darrien 08:42, 2005 May 14 (UTC)

I am an assistant professor of anesthesia at a Canadian teaching hospital. I have never heard of phosphoric acid used as a local anesthetic. Gresch, May 2, 2006, 17:40 UTC

[edit] bone calcium deficiency

5. i have just finished reading a book about phosphorus and its compounds. from what i've read so far, calcium deficiency is not the main cause for the bone degeneration, but lack of phosphates.

I think this is useless scaremongering lacking in real scientific evidence. -- Mac Davis] ⌇☢ ญƛ. 04:26, 23 March 2006 (UTC)
Wait...this would imply that phosophoric acid would promote calcium uptake in the bones. This is contrary to other FUDing i have read/heard/etc. Where did you read this? --M1ss1ontomars2k4 (T | C | @) 17:15, 1 November 2006 (UTC)

[edit] Reversion of anon deletions

Was that one of the above editors, accidentally logged out by timeout? The wiki syntax was messed up so I reverted, so I don't think it was a regular editor. - Leonard G. 05:34, 8 September 2005 (UTC)

[edit] melting point

This imho reliable source http://physchem.ox.ac.uk/MSDS/PH/phosphoric_acid.html gives a different melting point for phosforic acid (21C instead of 42C).

Acros, a big supplier of fine chemicals, also lists 21C on their website.

The same sources give also a different density (1.68 in stead of 1.9) and boiling point (158C vs 213)

[edit] Dispute

From what I understand the dispute seems to be over the effect of phosphoric acid on osteoporosis. The article cites few or no sources, so I'd like to add the following:

  • Wyshak G, Frisch RE. Carbonated beverages, dietary calcium, the dietary calcium/phosphorus ratio, and bone fractures in girls and boys. J Adolescent Health 1994;15:210–5.
  • Mazariegos-Ramos E, Guerrero-Romero F, Rodríquez-Morán F, et al. Consumption of soft drinks with phosphoric acid as a risk factor for the development of hypocalcemia in children: a case-control study. J Pediatr 1995;126:940–2.
  • Heaney RP, Nordin BEC. Calcium effects on phosphorus absorption: implications for the prevention and co-therapy of osteoporosis. J Am Coll Nutr 2002;21:239–44.
  • Brot C, Jorgensen N, Madsen OR, et al. Relationships between bone mineral density, serum vitamin D metabolites and calcium: phosphorus intake in healthy perimenopausal women. J Intern Med 1999;245:509–16.
  • Elmståhl S, Gullberg B, Janzon L, et al. Increased incidence of fractures in middle-aged and elderly men with low intakes of phosphorus and zinc. Osteoporos Int 1998;8:333–40.

But I am unfamiliar with citing practices for non-website sources. —The preceding unsigned comment was added by Tzenes (talk • contribs) 14:34, 12 April 2006 (UTC)

Thanks for finding those citations, Tzenes. I have managed to look up a few on http://scholar.google.com and those I have seen so far seem to vary from disproving the claim (e.g. Heaney and Rafferty which suggests there is a moderate association with high caffeine intake but not with phosphoric acid), through to showing it to be the opposite of the truth (e.g. [http://www.springerlink.com/(tepiar553cj1icrreazllhml)/app/home/contribution.asp?referrer=parent&backto=issue,5,13;journal,125,175;linkingpublicationresult

[edit] Use in soft drinks

Why is phosphoric acid used in soft drinks?

Norm

It's cheap, non-toxic, highly water-soluble, not too strongly acidic, and gives the kind of sour taste some people probably like. Citric acid, which has some similar properties, is also used in some soft drinks. H Padleckas 20:21, 25 June 2006 (UTC)

WTF? I thought it was to keep the caffeine dissolved in an environment in which it would otherwise crystallize out. --M1ss1ontomars2k4 (T | C | @) 17:17, 1 November 2006 (UTC)

[edit] Peerreviewer output

The following suggestions were generated by a semi-automatic javascript program, and may or may not be accurate for the article in question.

You may wish to browse through User:AndyZ/Suggestions (and the javascript checklist; see the last paragraph in the lead) for further ideas. Thanks, Wim van Dorst (Talk) 21:10, 26 June 2006 (UTC)


[edit] Orthophosphoric acid chemistry

In the final paragraph, this subsection discusses the dehydration of phosphoric acid. That phosphoric acid can be dehydrated by heating to metaphosphoric acid is supported by numerous references that I have found (though there is no mention in the article of the intermediate form of pyrophosphoric acid, which nearly every reference does mention). But the paragraph goes on to say that further dehydration leads to phosphoric anhydride (P4H10). This is, in a sense, true, since chemical dehydration of metaphosphoric acid will lead to this, but in the context of this sentence, it suggests that further heating would cause further dehydration. I can find no reference to support that -- indeed Merck 9th ed. says that metaphosphoric acid volatilizes at red heat. Hence it would be well nigh impossible to dehydrate metaphosphoric acid by heating. Karlhahn 14:21, 23 September 2006 (UTC)

There is the tendency to assume that heating many acids will cause dehydration, and this assumption might have crept into this article. A start in figuring out the facts would be to go beyond the Merck Index, which is bascially a handbook for physicians. I have been rewriting P4O10 article and have relied on Corbridge:
  • D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam. ISBN 0-444-89307-5.

What you are looking for might be difficult to find. I recommend deleting the paragraph that you suspect is misleading and re-writing it based on the facts known to you.--Smokefoot 15:01, 23 September 2006 (UTC)

I don't own the book you cite, so I hope you will let me know if somewhere it answers the question. For now I will do as you suggest, and then wait for such time as you can clarify the issue. Karlhahn 22:52, 24 September 2006 (UTC)

You can get futher dehydration of some of the acid salts of phosphoric acid by heating: this is used to make superphosphate fertilizers. From vague memory, I think that metaphosphic acid is the limit for dehydration of the free acid, but, even disregarding the vagueries of my memory, the experimenters may well have missed higher acids (I bet no-one has looked at the question for several decades). I would look and see what you can find on superphosphates, that may give an idea of what happens to the free acid. Physchim62 (talk) 13:21, 25 September 2006 (UTC)

I looked up monobasic sodium phosphate (NaH2PO4). On heating it loses all water and becomes sodium metaphosphate (NaPO3)n. I can find no source that this decomposes on further heating. I suspect, though, that if it is heated enough while mixed with SiO2 to absorb the sodium, you could, conceivably, distill P4O10 from the glassy melt. I don't know this for sure, though. Karlhahn 12:51, 26 September 2006 (UTC)
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