From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Chemistry (Rated B-class, High-importance)
WikiProject icon This article is within the scope of WikiProject Chemistry, a collaborative effort to improve the coverage of chemistry on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
B-Class article B  This article has been rated as B-Class on the project's quality scale.
 High  This article has been rated as High-importance on the project's importance scale.

This article has comments here.


I just wanna ask about the h4o bonded water a product from japan since 2007. the company has stated that "H4O -600mV is the most powerful hydrogen enhanced water with a perfect pH of 7.3. Hydrogen selectively eliminates free radicals, the ones that damage our cells. Hydrogen is the smallest molecule and since it is a gas it easily passes through your body. We measured an increase in hydrogen within the blood after drinking. H4O -600mV contains 1,500,000 times more hydrogen than tap water and 24 to 36 more times than alkaline electrolysis water. Most nutraceutical beverages are hot-filled and have preservatives, which keeps extends the expiration date by 1-2 years." Is there any validity to this given information? (vahn_dinio) 00:35, 27 July 2013 (UTC)

No. The talk about free radicals is gibberish, and an actual increase in hydrogen within the blood will kill you. — Preceding unsigned comment added by (talk) 21:27, 5 September 2013 (UTC)


Does H3O+ have its own boiling point? Does steam have H3O (thus a pH) after partially evaporating an acidic water? —Preceding unsigned comment added by (talk) 14:18, 23 July 2008 (UTC)

Solvation shells[edit]

  • ) I have added information from a recent article by MArkovitch & Agmon to the solvation section.

I would like to also add a picture and some more detailes, how can I do so?
I'd like to add the folloiwng picture: solvation shells energies. omermar

I don't think this is entirely appropriate for the general hydronium article. If the figure or related information can be found in the reference then I think it's enough for interested parties. Perhaps you can add to the Grotthuss mechanism page. Pigwiggle 18:36, 29 March 2007 (UTC)

Already in my to-do list. Thanks, Omer.

Some error ?[edit]


Two other well-known structures are the Zundel and Eigen cations. Eigen placed the hydronium ion at the centre of an H9O4+ complex in which the hydronium is strongly hydrogen-bonded to 3 neighbouring water molecules (3). Eigen proposed an H5O2+ complex, in which the proton is shared equally by two water molecules (4).


(3) Zundel, G. & Metzger, H. (1968) Energiebänder der tunnelnden Übershuß-Protenon in flüssigen Säuren. Eine IR-spektroskopische Untersuchung der Natur der Gruppierungen H5O2+ Z. Phys. Chem. 58 225-245.

(4) Wicke, E.; Eigen, M. & Ackermann, Th. (1954) Über den Zustand des Protons (Hydroniumions) in wäßriger Lösung. Z. Phys. Chem. 1 340-364.


Actually, I'm unable to verify the articles (not so easy), but there is probably something wrong:

-) The (3) is a Zundel's, not Eigen's, article.

-) From the article it seems that Eigen proposed both models, and it's not clear which is the Zundel and which the Eigen cations formula.

-) I'm quite sure that Zundel (not Eigen) proposed the H5O2+ structure. See, for example, J. Chem. Phys., Vol. 116, No. 2, 8 January 2002 (or simply the title of Zundel's article (3)). (But I could be wrong)

It doesn't matter who proposed what, but rather what the solvation structure is called. Pigwiggle

=) Actually, Eigens vision was that the H3O+ ion is better described as H9O4+, which includes the H3O+ and it's first solvation shell. This effects many properties, for example - the diffusion of this larger structure will be slower. We have recently reported energetics of the hydronium solvation shells and found that the hydrogen bonds between the H3O+ and it's first solvation shell are indeed quite strong. I'll post a link to the article (from Journal of Physical Chemistry A) soon. omermar 07/03/2007

oxonium and hydronium ions are different[edit]

an oxonium ion is R3O+ and can be hydronium but also a protonated ketone or aldehyde, I propose to split of oxonium to the more general meaning V8rik 22:39, 9 August 2005 (UTC)

Well, that's based off the solvent system definition isn't it? In which case, that would be the Solvonium, or <anything>-ium relative to dissociation of afforementioned compound/molecule. Beside that, the OXO is the IUPAC prefix for oxygen -- if there is a functional bonding atom it'd be named off what that was; ammonium, phosphonium, iodonium. Get your IUPAC Systematic Substitutive Nomenclature books :-3 SConfident.gif J O R D A N [talk ] 15:47, 8 May 2007 (UTC)
Take a peek here SConfident.gif J O R D A N [talk ] 15:50, 8 May 2007 (UTC)

Isn't the IUPAC name actually HYDROXONIUM? 12:40, 19 March 2006 (UTC)

maybe, but no one uses it.Pigwiggle 16:17, 30 March 2006 (UTC)
No one uses it? I don't think so. "Hydroxonium" is the term used in the syllabus I'm studying. My textbook and a few textbooks from other publishers are also using this term. Using Google, I found 19,600 results.[1]

that doesnt matter. what matters is what it is. Javsav 11:00, 3 September 2006 (UTC)

Fine, but don't get all excited about moving the page or anything. Folks will be coming here to read about the hydronium cation. I'm exceedingly familiar with the literature and absolutely everyone uses hydronium. I don't recall ever reading oxonium or hydroxonium. I'd bet the farm hydronium is used exclusively in the page references. Pigwiggle 14:38, 5 September 2006 (UTC)

I am from Hungary and here it used to be called hidroxonium but now the official name is simly oxonium. May it have happened to the english name, too? —Preceding unsigned comment added by (talk) 12:13, 5 January 2008 (UTC)

Pure Hydronium?[edit]

Can you make pure hydronium?

=) I suppose you could, if you took a measured quantity of a strong mineral acid (HCl or some such) and added an equal amount of moles of pure water to it. If you then filter out the anions (Cl) by putting it through a membrane, you would be left with hydronium.

doubt it; you would have a huge charge deficit not to mention two highly reducing/oxidizing solutions Pigwiggle 16:20, 30 March 2006 (UTC)

=) I agree. The closest you can do is highly acidic solution, but then you will also have the counter ion. For example - adding lots of HCl will increase your eigen/zundel cations, but would also leave Cl-. What you can do is simulate pure hydronium; We have recently reported for the first time the energetics of hydronium solvation shells (In journal of Physical Chemistry A). I'll post a link here soon. omermar 07/03/2007

The only way you can have pure hydronium is in the gas phase. Not something you would store in a bottle, though. --Itub 10:20, 9 May 2007 (UTC)
You can make pure hydronium (i.e., H3O+ instead of larger clusters) with a counterion simply by making the monohydrate of a strong acid such as triflic. But there's no way you can "filter out the anions".Tressure 21:59, 7 June 2007 (UTC)

Unless you could somehow make the hydronium ions adopt a metallic state, similar to the theorized metallic hydrogen. Then you could filter them out in pure form. This would require extremely high pressures (it might not even be possible to do so at all without decomposing the ions, however). Stonemason89 (talk) 14:18, 26 May 2008 (UTC)

Nope, because hydronium is a cation, while hydrogen (metallic or not) is electrically neutral. Perhaps you could make a "metallic H3O", but not a "metallic H3O+". --Itub (talk) 09:53, 4 November 2008 (UTC)
You can make pure hydronium by using a voltage clamp; a pipette with a positively charged cathode (wire attached to battery). The cathode will attract the conjugate anion in the mineral acid, say Cl- in HCl. The stronger the cathode and with increasing treatments, you will increase the hydronium concentration relative to the conjugate anion. — Preceding unsigned comment added by (talk) 01:55, 30 January 2013 (UTC)


The pKa given for the hydronium ion is meaningless. The Ka for hydronium is the equilibrium constant for the reaction H3O+ + H2O <-> H2O + H3O+. This is a null reaction (products are the same as the reactants), so the equilibrium constant is, by definition, one. The Ka given of 55.5 is calculated by ignoring the concentration of water as a reactant (because it's a solvent), but -not- ignoring it as a product. I can think of few conventions which are sillier.Tressure 21:56, 7 June 2007 (UTC)

No, the value given is correct. We are comparing it to other pKas in which the solvent (water) is omitted but the product (deprotonated species, in this case happens to be water as well) is not. This means we can compare it to other acids. (talk) 13:23, 3 November 2008 (UTC)
This has been discussed several times in the Journal of Chemical Education, and both positions have been advocated. The strict thermodynamic point of view is that K = 1 (and similarly, Ka = Kw = 10^-14 for the acidity of water itself). The activity of water is 1 because it is the solvent, and there are no grounds for distinguishing between "reactant water" and "solvent water" in the equilibrium. However, some authors prefer to make this arbitrary distinction in order to facilitate comparison with other acids. See J. Chem. Ed. v. 68, p. 305; 64, 1067; 82, 999; 83, 1290; and 63, 473.
A key point is that the acidity (self-ionization) of a pure substance is not directly comparable with the acidity of a dilute solute in water, which is what one normally represents with a pKa. However, one can make the following thought experiment to come up with the famous Ka = 55.5. Imagine a 1 M solution of "H3O*+" in water, where the asterisk means a labeled oxygen such as oxygen-18. Assuming no equilibrium isotope effects, what will happen? Since the excess proton has no preference towards either type of oxygen, it will simply get diluted; as "normal oxygens" outnumber "labeled oxygens" 55 to 1, only 1/55 of the excess protons will end up bound to an oxygen-18 atom. The result: an equilibrium constant of 55. But this only arises because we distinguish between the "acid", for which the reference state is 1 M, and the "solvent", for which the reference state is the pure solvent. --Itub (talk) 10:10, 4 November 2008 (UTC)

Picture of Hydronium Ion[edit]

Can somebody please add details about the bond length and bond angles of the ion in the molecule picture? —Preceding unsigned comment added by Chemfreak20 (talkcontribs) 12:33, 6 October 2008 (UTC)

Zundel Cations[edit]

Who are Zundel cations (mentioned in the article) named after? If I just type "Zundel" into the search box, it takes me to an article about a neo-Nazi. I'm assuming he's not the same guy that discovered Zundel cations, but you never know.

It would be useful to clarify exactly who the eponymous Zundel is, and maybe provide a link to the article about him on WP, if one exists (if not, then one should probably be created since he's definitely notable enough to have one, if he had the H5O2+ cation named after him). Stonemason89 (talk) 18:24, 4 November 2008 (UTC)

It is named after Georg Zundel. There is an article about him in the German Wikipedia (de:Georg Zundel). --Itub (talk) 19:29, 4 November 2008 (UTC)

Requested move - January 2009[edit]

The following discussion is an archived discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the proposal was

Declined, per WP:SNOW. --Rifleman 82 (talk) 05:04, 14 January 2009 (UTC)

There are two articles: Hydron (chemistry) about H+ ions in a general scope, and this article (currently Hydronium) about an aqueous form of that ion. Of course, these are distinct notions (former is wider, latter is narrower), but is there a difference in their names? Hydronium is a general name for the hydrogen cation in latin form, which is anglicized as hydron (cf. Latin: hydrogenium — English: hydrogen). The fact that H+ in aqueous chemistry is referred as hydronium (== hydron) means that scientists do not emphasize that the ion is aqueous, which may be evident in that context, or is not significant at all. To eliminate the ambiguity, I propose the following:

Incnis Mrsi (talk) 18:23, 10 January 2009 (UTC)


  • Oppose this would violate the meaning in every introductory chemistry text I've ever seen. H3O+(aq) is the normal meaning of "hydronium", your suggestion is not. (talk) 22:28, 10 January 2009 (UTC)
    But H3O+(aq) is a form of hydron, isn’t it? So what violation? Please, provide reliable sources concerning the normal meaning of. Incnis Mrsi (talk) 22:59, 10 January 2009 (UTC)
  • Strongly oppose. The IP editor above is correct. H3O+(aq) is always referred to as hydronium not hydoxonium. Hydron is another term for the proton and is different from the hydronium ion. H3O+(aq) is not a form of hydron. That article is about H+ not H3O+. --Bduke (Discussion) 23:33, 10 January 2009 (UTC)
    Fist half is false. This ion is also referred as hydoxonium[2][3] d:hydroxonium Image:Hydroxonium-cation.png — use Google. Please, provide reliable sources on the second half of your statement, that H3O+(aq) is not considered as a form of hydron. Incnis Mrsi (talk) 09:13, 11 January 2009 (UTC)
  • Oppose since hydron refers to H+(see [4]) and hydronium refers to H3O+ (see Phys. Rev. Lett. 51, 554 - 557 (1983), Chem. Phys. 110, 6766 (1999), etc.). Both are stable gas phase ions and have quite different properties. --Kkmurray (talk) 23:43, 10 January 2009 (UTC)
    Only the article of 1983 is strictly relevant to the naming question, because the latter is about H+·[H2O]n+1, aquatic forms of hydron (== hydronium). One case of an erroneous term use over 26 years is not too much. Please, provide more reliable sources on your claims that the word hydronium is not just an alternative form of the hydron, but a distinct scientific term, which is not a synonym of hydron. Incnis Mrsi (talk) 09:13, 11 January 2009 (UTC)
Note that the 1999 Hodges and Stone paper defines hydronium–water clusters as "H3O+... (H2O)n clusters" and that they are modeling the interaction between hydronium and a water cluster and not a proton and a water cluster. For more recent papers limited to ACS Journals with hydronium in the title, there are 76 hits between 1956 and 2008.[5] The use of hydronium in these works appears to support the consensus here. Google Scholar reveals additional examples (>600 in the past year). --Kkmurray (talk) 16:11, 11 January 2009 (UTC)
  • Strong Oppose. Hydronium is technically correct and in common usage for H3O+. Hydron is obscure, and does not specifically refer to H3O+. Hydroxonium is not a word I've ever heard of before, and I've taught chemistry. Yilloslime (t) 00:21, 11 January 2009 (UTC)
    Of course, Hydron does not specifically refer to H3O+. Is it bad? Incnis Mrsi (talk) 09:13, 11 January 2009 (UTC)
    The point is that every textbook on my shelf, and probably yours, and almost certainly every text in use chemistry courses today refers to H3O+ as hydronium rather than hydroxonium. Yilloslime (t) 17:36, 11 January 2009 (UTC)
  • Strong Oppose per all the above. Vsmith (talk) 03:02, 11 January 2009 (UTC)
  • Neutral - There are reputable text books who use the term hydroxonium ion rather than hydronium ion e.g. Greenwood, Cotton and Wilkinson. Hydron (according to Huheey Keiter and Keiters Inorganic Chemistry) is a naked proton and all hydrated forms except for the H3O+. Perhaps there is an inorganic/organic chemistry divide here? Typically few follow IUPAC who deprecate hydronium and recommend oxonium or oxidanium. --Axiosaurus (talk) 18:02, 11 January 2009 (UTC)
  • Comment. Yes, it does seem that hydroxonium is used sometimes. However hydronium seems to be much more common. A google search on hydronium gave 156,000 hits, while one on hydroxonium gave 12,100. It therefore seems appropriate for hydroxonium to be a redirect to hydronium and mentioned on that page. That is exactly the current situation. A google search on hydron is confused by contact lenses and other business names. Hydron seems generally to refer to the proton but not H3O+. Oxidanium gets few google hits and oxidanium is a redirect to hydronium. Oxonium is a disambiguation page and oxonium ion refers to a class of compounds with a positive charged oxygen with three bonds, so hydronium is a special case of an oxonium ion. The evidence seems clear to reject this proposed merge and leave things as they are. --Bduke (Discussion) 22:42, 11 January 2009 (UTC)
Hydrogen ion has recently been added to the "see also" of hydronium. It gives a good summary of the various uses and defines hydron as a proton, deuteron or triton, i.e. H+ irrespective of the isotope. --Bduke (Discussion) 22:53, 11 January 2009 (UTC)
  • Oppose having taken a year and a half of chemistry so far, I have yet to see "hydronium" be called anything but "hydronium" and have any meaning outside of the well known cation that forms during the self ionization of water. —harej // change the rules 04:10, 12 January 2009 (UTC)
  • Oppose per Yilloslime; is it WP:SNOWBALL time yet? :) --Quuxplusone (talk) 08:21, 13 January 2009 (UTC)
  • Oppose as per above. Walkerma (talk) 04:53, 14 January 2009 (UTC)


The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Hydroxonium/Hydronium and IUPAC[edit]

The page for Acid–base reaction states that IUPAC is depreciating other terms in favor of "hydronium", and the hydronium page states that IUPAC prefers hydroxonium. It is unlikely that these are both correct, anyone have a firm reference on this? Daviga1 (talk) 04:52, 2 August 2009 (UTC)

Salts and Hydro"di"um[edit]

Is it possible to create a salt of hydronium, or will any attempt just decompose into an acid and water? Secondly, since water has two free electron pairs, is there any evidence for H4O2+? —Preceding unsigned comment added by (talk) 02:14, 24 October 2009 (UTC)

1) yes, see Hydronium#Solid_hydronium_salts. 2) yes, see J. Am. Chem. Soc., 1986, 108 (5), pp 1032–1035, Chem Phys Lett, 140 (6) pp.579-581 and a handful other articles. --Cubbi (talk) 02:26, 24 October 2009 (UTC)
Thank you! All of you are really helpful for these little ivory-tower curiosities. (talk) 02:30, 26 October 2009 (UTC)


Would it possible for a bond to form between an O and an O+, and then a hydrogen and the O and two hydrogens and the O+?

Like this:

  > O+ - O - H

A sort of hydronium-peroxide? (talk) 12:22, 3 November 2009 (UTC)

It's very possible. See Hydrogen_peroxide#Alkalinity.—Tetracube (talk) 16:00, 3 November 2009 (UTC)
Wow! That's great. Thanks! (talk) 20:25, 3 November 2009 (UTC)


The pH given is 7.0 - should it not be stated that this varies with temperature, and it can still be neutral with a pH of 3, for example? Smaug123 (talk) 23:43, 27 December 2009 (UTC)


Is the diameter of this ion determined by some method?-- (talk) 15:57, 15 April 2011 (UTC)

pH again[edit]

This needs to be fixed: "In pure water, there is an equal number of hydroxide and hydronium ions so it has a neutral pH of 7."

That is confusing, and arguably incorrect. It is my understanding that pH = 7 means there are 10e-7 hydrogen cations per liter, not that there are equal numbers of anions and cations. That happens to be the case, but only because the reaction creating the ions is in equilibrium. Someone more knowledgeable than I should fix it.

Semantics. A number cannot be equal. Better is "there are equal numbers of hydroxide and hydronium ions." (talk) 21:33, 11 April 2012 (UTC)

Hydronium structure/lifetime in neutral water and in a strong acid[edit]

I was wondering about the following sentence in the article which I think is important but which has no reference:

"Unlike hydronium in neutral solutions that result from water's autodissociation, hydronium ions in acidic solutions are long-lasting and concentrated, in proportion to the strength of the dissolved acid."

I wonder if I can get more information/references on this particular point.

— Preceding unsigned comment added by (talk) 14:04, 20 January 2013 (UTC)

Isotopic effects[edit]

Deuterated hydronium ions - detection by mass spectrometry : JCP-- (talk) 09:32, 27 June 2013 (UTC)

Also this: [6]. --Kkmurray (talk) 02:02, 9 August 2013 (UTC)

pH again[edit]

In the article on pH, the pH is defined to be the logarithm of a dimensionless constant, the activity of hydronium, but in this article, it is asserted that a pH of 7 corresponds to a negative logarithm of ten to the minus seventh moles per liter. So which is it? To find the pH, to we take the log of hydronium's molarity, or its activity? Rwflammang (talk) 20:40, 28 January 2014 (UTC)