Talk:Henry's law

From Wikipedia, the free encyclopedia
Jump to: navigation, search
          This article is of interest to the following WikiProjects:
WikiProject Physics (Rated B-class, Mid-importance)
WikiProject icon This article is within the scope of WikiProject Physics, a collaborative effort to improve the coverage of Physics 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.
 Mid  This article has been rated as Mid-importance on the project's importance scale.
 

This article has comments here.

WikiProject Chemical and Bio Engineering  
WikiProject icon This article is within the scope of WikiProject Chemical and Bio Engineering, a collaborative effort to improve the coverage of Chemical and Bio Engineering articles 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.
 ???  This article has not yet received a rating on the project's quality scale.
 ???  This article has not yet received a rating on the project's importance scale.
 
WikiProject Citizendium Porting    (Inactive)
WikiProject icon This article is within the scope of WikiProject Citizendium Porting, a project which is currently considered to be inactive.
 
This article has an assessment summary page.

In relation to climate change[edit]

I've only just started looking, but it seems to me that Henry's Law presents a problem for the hypothesis that CO2 causes global warming. Should we investigate and see if anyone in the scientific community's are asking this same question? Leighblackall (talk) 00:37, 15 November 2009 (UTC)

Could you elaborate on this? I think this is exactly what is concerning about CO2 causing/influencing global warming. As the earth warms and causes more CO2 to be released from the oceans it will cause faster/more warming. --Chemboss (talk) 19:46, 24 October 2013 (UTC)

Reason for moving some of the article[edit]

I have moved the text below from the article to here, because it's not very encyclopaedic, and I'm sure a less-than-cursory search of the literature would shed some light on it. I don't know enough to say what of this is accurate and what's not - hope someone else might. Worldtraveller 22:43, 26 Mar 2005 (UTC)

Addendum 2005
A cursory search of the literature has not revealed what effect a temperature difference between gas and liquid would have. It is hereby maintained that increasing the temperature of either medium has the effect of increasing the partial pressure or concentration of that medium.
When a temperature difference is introduced the effect of this addendum is to cause thermal diffusion with flow of solute molecules from warm to cool in the liquid solvent and across the gas/liquid interface as required to achieve a new balance.
This mechanism can be demonstrated by filling a glass with freshly opened soda water from the refrigerator and putting a fresh ice cube from the freezer in the liquid. It will be observed that gas bubbles do not precipitate on the glass as one might expect, because of reduced solubility, but rather on the ice. This demonstrates that carbon dioxide molecules flow down the temperature gradient in the liquid and across the liquid surface from a relatively dilute solution into 100% carbon dioxide. This is a very potent thermal diffusion effect considering that temperature differences are very small.
Further note 2006
Henry's Law can be used to prove that interface diffusion does occur. Should the solute concentration in either medium be changed the concentration in the other has to change to produce a new balance. For this to happen there must be diffusion across the interface, something that is not accepted by mainstream climatology.
If interface diffusion is not accepted then of course a thermal diffusion effect cannot be accepted.
It could be argued that the carbon dioxide example chosen does not obey Henry's law because it reacts with water to form a carbonate. In addition there is, as far as I know, no listing for thermal diffusion for the transport of matter in Wikipedia, only for heat dispersion. Thermal diffusion of matter is well known to happen. Hydrogen,for example, migrates down the temperature gradient in zirconium alloy pressure tubes. It seems however, to have been missed and since it was, and since CO2 is not ideal, it was assumed that there would be sufficient grist for a challenge.

== The values for oxygen, carbon dioxide and hydrogen have the wrong units ==

The following values of the Henry's Law constants are those given in the current article:

*O2 : 4.34×104 L·atm/mol>/s>

*CO2 : 1.64×103 L·atm/mol

*H2 : 7.04×104 L·atm/mol

The units above are incorrect are incorrect. The correct units are:

*O2 : 4.34×104 atm/(mol fraction)

*CO2 : 1.64×103 atm/(mol fraction)

*H2 : 7.04×104 atm/(mol fraction)

See [1] which gives almost exactly the same numerical values as given in the current article but also has the correct units:

*O2 : 4.32×104 atm/(mol fraction)

*CO2 : 1.64×103 atm/(mol fraction)

*H2 : 7.06×104 atm/(mol fraction)

Also see [2] and download the .pdf file listing a great many Henry's Law constants. This source defines k = C/P which is the inverse of the k=P/C used in this Wikipedia article. Therefore, the values from the downloaded .pdf file were inverted to obtain:

*O2 : 769.2 L·atm/mol     which converts to 4.27×104 atm/(mol fraction)

*CO2 : 29.4 L·atm/mol     which converts to 1.63×104 atm/(mol fraction)

*H2 : 1282.1 L·atm/mol     which converts to 7.12×104 atm/(mol fraction)

Also note that the downloaded .pdf file uses the solution molarity, M = (mols of gas)/(liter of solution) to express the concentration C of the solution ... which is the same as using mol/L.

As can be seen, both of the sources I have referenced above are in very close agreement with each other. I am accordingly revising the values in this Wikipedia article to show the correct units.

I must say that I am dismayed that the incorrect units were not noticed much earlier. - mbeychok 05:46, 14 June 2006 (UTC)

Is Like-A-Fish really relevant to this article?[edit]

I don't want to be a spoil sport but are Like-A-Fish in the "See also" section and New 'no air tanks' diving system, based on Henry's law in the "External links" section really relevant to this article? To me, they seem to be advertising for the same company. I really see no connection between that diving air invention and Henry's Law. Am I being too harsh? - mbeychok 06:27, 14 June 2006 (UTC)

I've removed the Like-A-Fish link since it compounded the feeling of advertising for me too, and it pointed to a non-existent page anyway. But the news article does actually mention Henry's law and explains the device's function based on lower pressures releasing dissolved gas, so there is some relevance and it might get a non-scientist more interested after seeing an application with such potential. ObfuscatePenguin 09:45, 18 August 2007 (UTC)

Speaking of, and to, non-scientists: It seems that one of the things Inventor Bodner has to explain to people, even before he can get into what his invention is all about, is that there are two forms of oxygen in water: molecular oxygen dissolved in water; and then there's the O which is the oxygen of H2O . We want to talk about the fine points of Henry's law, but I've found that quite a few of the public out there doesn't actually grok that gases dissolve in liquids, pretty much the same way that sugars and salts dissolve in liquids. Another thing that confuses people is when it's pointed out that the solute and the solvent can't react with each other, if you want to describe the situation with Henry's law. An example of this is given in the article for carbon dioxide. I think it would be a good idea to generalize this by saying that Henry's law describes any gas/liquid system that is at equilibrium, and a static equilibrium at that. So if for example a lot of fish were pulling the oxygen out of the water in a lake, that disturbs the equilibrium just like the carbon dioxide turning into carbonate. (Somebody please rattle my cage here if that's in error.) Richard8081 24.7.73.231 19:47, 29 August 2007 (UTC) There's always this push/pull of wanting to make sure that everything in an article is elegantly and adequately described by the appropriate equation (which makes the fish a real problem, editorially and equation-wise) and wanting to tie it all into the real world (where there really are reactions taking place in the water that are of GREAT interest, including people who want to go diving!) This comes up all the time for me when I'm trying to explain to people why shake flasks don't work in microbiology labs; the bugs growing in the flask are consuming the oxygen faster than diffusivity allows it to be replenished, hence most of the shake flasks in the laboratories of the world are running at zero oxygen. Richard 8081 24.7.73.231 19:29, 29 August 2007 (UTC) Richard8081 20:10, 29 August 2007 (UTC)

Reason for modifying the table[edit]

The table which user:NickFr added to this article is very helpful and enhances the article. I modified it somewhat to make the definitions of the parameters more explanatory or precise. I also modified the sections above the table so that they were consistent with the table. - mbeychok 19:59, 30 August 2006 (UTC)

Reason for deleting most of Sept. 17, 2006 edit by 66.27.139.36[edit]

The edit by 66.27.139.36 had some interesting material about carbonic acid but most of it had absolutely nothing to do with Henry's Law. It really belongs in a more appropriate article or in an article of its own. I left in the one sentence "A common example of a gas that reacts with the solvent is carbon dioxide, which reacts rapidly with water to form hydrated carbon dioxide and then forms carbonic acid (H2CO3)." because that sentence is appropriate here ... but all the rest of the edit was deleted. - mbeychok 21:14, 17 September 2006 (UTC)

Reason for reverting changes by 129.2.198.192[edit]

129.2.198.192:

If you will read the entire article, especially the section on Other Forms of Henry's Law, it discusses the fact that the equation you used is simply the invert of the original equation. The examples given in units of L•atm/mol are correct for the original equation and incorrect for your inverted version. See the table in the section on "Other Forms of Henry's Law".

Please do not change the equation again. Regards, - mbeychok 19:03, 6 December 2006 (UTC)

Reason for reverting changes by 69.200.224.11[edit]

69.200.224.11:

This has come up before ... see the comment just above. It applies to your changes as well. Read the entire article and read it thoroughly. Please do not change the equation again. Regards, - mbeychok 00:08, 21 January 2007 (UTC)

I see that you have changed it back, so please disregard my above remark. But please be careful when experimenting like that. - mbeychok 00:33, 21 January 2007 (UTC)

Interpretation of Henry's Law[edit]

I am using Chemistry Matter and its Changes by Brady and Senese (5th edition), which claims the formula for Henry's law is infact:

Cgas = kHPgas  

where C is the concentration of the gas, P is the partial pressure, and k is Henry's law constant. This article claims that it is:

p = kc

please review for me. Pillowmurder (talk) 19:06, 25 October 2008 (UTC)

Pillowmurder , if you will carefully read the entire article ... not just the first section ... you will see that there are indeed many different ways to express Henry's Law. In fact, the one in your textbook is in the second vertical column of Table 1 in the article. Each of the ways shown in Table has its own set of measurement units for the Henry's Law constant. Regards, mbeychok (talk) 19:55, 25 October 2008 (UTC)

Dear Mbeychok, I did in fact read the entire article. Forgive my ignorance, I am just a bit confused. Does that mean that a single gas has multiple proportionality constants for the different ways of expressing Henry's Law? My chem book (which I admit is for novices) doesn't explain this. I also looked over the Spanish page which emphasized C = kP.Take care and thank you for your time!Pillowmurder (talk) 03:44, 26 October 2008 (UTC)

This article does a good job of describing Henry's law, but fails to give an explanation of why it is true. I found a reference page[3] that discusses the matter, but in an unscientific manner. I believe that a section similar to the following should be added to the article.

Henry's law can be explained by the fact that there is a fixed probability that a gas molecule will encounter the surface of a liquid. Similarly, there is an equal probability that a gas molecule dissolved in the liquid will escape the surface of the liquid and return to the gas. Since these two quantities are equal, the rate of dissolving and undissolving of a type of gas are equal. Thus, there is a constant but equal exchange of any one type of gas molecule between the liquid and the gas mixture that is determined only by the concentration of that type of gas.[4]

Ok, that's a start, but it's a bit wordy. Please recommend any changes that need to be made to improve it.

Is there another term for undissolve?

Is the reference I provided good enough for encyclopedia use?

Doctorrockandroll 02:19, 3 February 2007 (UTC)doctorrockandroll

To answer your final question quite candidly, my opinion is that it is not good enough for use here. To me, it is written down at about the level of a 10-12 year old pre-teenager.
Also, when you start using words like "molecule", "probability", and "concentration of gas" you defeat your own purpose of trying to write down to the level of pre-teenagers because they won't know what those terms mean. They may think they do, but they won't really understand them. As for "gases undissolving", one could use "gases escaping from the liquid solution".
In general, I oppose writing down or speaking down to readers to the point where the technical integrity of the article is no longer maintained. I don't think you would find the sort of explanation (as you propose) in the Encyclopedia Britannica and I see no reason why a technical article in Wikipedia should be written for pre-teenagers. For example, I see where you did some minor editing of the Intermediate frequency article's mention of "superheterdyne receivers". I haven't the faintest notion of what is meant by "intermediate frequency" or "superheterodyne receivers" ... but I don't expect that article to dumb itself down to where I understood it. If I were interested in radios and wanted to understand that article, I would buckle down and do some studying and reading until I did have enough knowledge to understand it. - mbeychok 06:01, 3 February 2007 (UTC)

Reason for reverting change of equation by 155.198.109.41[edit]

55.198.109.41:

If you will read the entire article, especially the section on Other Forms of Henry's Law, it discusses the fact that the equation you used is simply the invert of the original equation. The examples given in units of L•atm/mol are correct for the original equation and incorrect for your inverted version. See the table in the section on "Other Forms of Henry's Law".

This has happened a number of times before because people do not read the entire article thoroughly before making a change. Please do not change the equation again. Regards, - mbeychok 17:42, 6 March 2007 (UTC)

Converting between the constants units[edit]

How does one convert between a K with the unit Atm/(mole fraction) and L*Atm/mol ? Thanks 67.79.200.162 22:14, 28 March 2007 (UTC)confused person

I assume that you meant to ask about the Henry's law k (rather than K). The easiest way to convert between the two units you asked about is to use the values in Table 1 of the article to find that:
L*atm/mol = [atm/(mol fraction)] ÷ 55.4
If you want the actual dimensional conversion, send me your email address and I will send it to you as a Microsoft Word document. To email me, go to my user page, scroll down the left hand frame and click on "Email this user". - mbeychok 22:56, 28 March 2007 (UTC)
Thank you for your help. They differ by a factor of approximately 55.4 up or down a little depending on the gas. This weekend I will figure out the conversion when I don't have to spend most my time working. Anyways, over at <a href="http://webbook.nist.gov/cgi/cbook.cgi?ID=C64175&Units=SI&Mask=10#Solubility">NIST</a> here are henry's constants and they use mole/kg*bar. The reason this all sparked my interest started on <a href="http://forums.austin.craigslist.org/?ID=60666084"> craiglist forum.</a> The best way to look at situation is see slope of rault's law and henry's law I thought but I got hung up on units. 67.79.200.162 16:19, 30 March 2007 (UTC)confused person
My offer to email you the conversion is still open. The reason the conversion factors you found in Table 1 vary slightly from 55.4 is not because the gases are different ... they differ slightly because of rounding off of the various k values.
I am not surprised that NIST used other dimensional units. I have seen, quite literally, a dozen or more different dimensional units being used in the technical literature.
As for the conversion, when you determine the liters of solution per mole of solution, just ignore the gas dissolved in the solution ... it will be insignificant when compared to the amount of water. Also, most reported values are based on the grams of water per liter of water at 20 degrees C (i.e., 998 g/L). - mbeychok 20:54, 30 March 2007 (UTC)
I get it now. The aproximation through me off I think. For example:
k=120 mol/kg*bar*(1kg/1000g)*(18g/mole water)*(atm/1.01325 bar)= 2.13 atm and can be used for mole fraction equation as slope for previously mentioned problem. Sometimes those approximation can be difficult. Thanks for the help 70.113.83.253 00:47, 31 March 2007 (UTC)less confused person

Error in the temperature dependence section[edit]

There's an obvious (i.e. to me) error in the formula for the k temperature dependence. There is a minus sigh missing in front of the C constant. In the form we have now, the partial pressure of a gas dissolved in a liquid decreases with increasing temperature. It is a nonsense: it should obviously increase. Otherwise warm Coke would not degas (it degases when the partial pressure of CO2 inside the Coke is greater then its partial pressure in the air).

No, it is not nonsense! The solubility of a gas does decrease with increasing temperature. That is exactly why carbonated cold drinks degas when they warm up. - mbeychok 15:07, 21 April 2007 (UTC)

Both the formulas above and below the C value table have wrong signs of the C constant. You can compare the formulas with the correct versions in the file linked as Reference 3 in the article. Because I am unable to change the sign in the formulas (which are graphics), I changed the signs it in the table, which is not an optimal solution but also make the section correct for now (our C is negative of the one given in reference 3). -Friendly Neighbour 12:23, 21 April 2007 (UTC)


No, the sign of C is correct as it was before your edit. It should be positive. It takes a very close reading of all of Reference 3 to see that. I note (as you state just below) that you have now reverted your edit so that the sign of C is back to being positive. Thanks for correcting your mistake. - mbeychok 15:16, 21 April 2007 (UTC)
The formulas are not graphics. My mistake. I corrected now the formulas and reverted my table changes. BTW, now the temperature dependence formula has the same sign as the one in the following section (if you notice that β ~ 1/T). -Friendly Neighbour 12:34, 21 April 2007 (UTC)
The negative sign (in front of the C) in the equation must also be removed to yield a decreasing solubility for increasing temperature. For example, do the math for T = 398 K and T_\theta = 298 K and using C = 1700.
I accordingly removed that negative sign and left the equation as it was before your edits. - mbeychok 16:01, 21 April 2007 (UTC)
You're wrong. The formula is not for solubility but for partial pressure. As solubility decreases with temperature, partial pressure must increase. Otherwise the surplus gas could not diffuse to the air. Believe me, I am teaching the subject to graduate students. And if you do not believe me, compare your formula with the one used in Reference 3 in the article. Also your formula has the inverse sign to the identical one (but written in a different convention) in the next section. -Friendly Neighbour 18:15, 21 April 2007 (UTC)

Your mistake is probably to believe that c in Henry's Law is the solubility (maximal concentration that can be solved in the given temperature). No, it's simply a concentration. The concentration that of the gas which is actually present in the liquid. Henry's Law simply shows us the partial pressure of the gas (the pressure the gas would have in a neighboring volume to be in balance with the liquid). When temperature increases, c remains constant (conservation of mass) unless the gas dissolves into or from the liquid. It is the partial pressure which changes. When we heat the liquid, partial pressure has to increase to let the gas dissolve from the liquid (the outside partial pressure does not change and gas dissolves by definition of the partial pressure to the substance with a lower one). Compare what I say to (for example) the first paper I found on the subject. The formula in its abstract gives us a clearly increasing function of the partial pressure of CO2: log 10 P CO2 = A - B /( t + 273), where A = 15.26, B = 7850. It's not important what pressure units they use (I've checked: it's bars) but the results clearly show an increasing function:

t [C]              T [K]          p [bar]
0.0000          273.0000        3.2020e-14
5.0000          278.0000        1.0534e-13
10.0000         283.0000        3.3226e-13
15.0000         288.0000        1.0071e-12
20.0000         293.0000        2.9389e-12
25.0000         298.0000        8.2740e-12
30.0000         303.0000        2.2512e-11
35.0000         308.0000        5.9291e-11
40.0000         313.0000        1.5140e-10
45.0000         318.0000        3.7538e-10
50.0000         323.0000        9.0489e-10

I hope you will not revert me before you try to understand your mistake. -Friendly Neighbour 18:49, 21 April 2007 (UTC)

Two more sentences for you, in case all I wrote before did not convince you: "The pCO2 in surface ocean waters doubles for every 16 C temperature increase (d ln pCO2/dT = 0.04231 C-1 Takahashi et al., 1993). For a parcel of seawater with constant chemical composition, its pCO2 would be increasedby a factor of 4 when it is warmed from polar water temperatures of about -1.9 C to equatorial water temperatures of about 30 C". Its from Takahashi et al. 2003 "Global sea–air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects". Would it make any sense if your version of the van't Hoff law were true? -Friendly Neighbour 19:24, 21 April 2007 (UTC)

Yes, the partial pressure of a gas in solution increases with temperature. But the solubility of the gas decreases with increasing pressure. One is the inverse of the other. The temperature dependence section of the article clearly states "It can be seen that the solubility of gases is decreasing with increasing temperature."
Look at Table 1 in the article which provides the various forms of k and the corresponding various dimensional units. It has k_{H,pc} and k_{H,cp} and one is simply the inverse of the other. The units of k_{H,cp} are given in that table as (mols of gas)/[(liter of solution)/(atm of gas partial pressure)} ... which a great many of us very commonly refer to as the solubility of the gas. The temperature dependence equation was very carefully written using the k_{H,cp} form and that form does decrease with temperature. Therefore, the equation sign before the constant C must be deleted so that k_{H,cp} will decrease. As I said before, "For example, do the math for T = 398 K and T_\theta = 298 K and using C = 1700" and you will see that negative sign before the constant C must be deleted in order for k_{H,cp} to decrease.
The paragraph below Table 1 in the article also clearly states As can be seen by comparing the equations in the above table, the Henry's Law constant k_{H,pc} is simply the inverse of the constant k_{H,cp}. Since all k_{H} may be referred to as the Henry's Law constant, readers of the technical literature must be quite careful to note which version of the Henry's Law equation is being used.
Please reconsider your edit and your statement that "In the form we have now, the partial pressure of a gas dissolved in a liquid decreases with increasing temperature. It is a nonsense: it should obviously increase." I agree that such a statement would be nonsense. But that is not what the temperature dependence section said. It said the solubility would decrease with increasing temperature and, for that reason, the k_{H,cp} form was used.
If you feel some rewording is needed to make it easier to understand that the temperature dependence section is talking about solubility and k_{H,cp} (rather than partial pressure and k_{H,pc}), then do some rewording ... but please remove your negative sign in front of the constant C. - mbeychok 20:10, 21 April 2007 (UTC)
Also, can we please carry on our dialogue without using the words "your mistake" and "nonsense" any more? Thanks, - mbeychok 20:16, 21 April 2007 (UTC)
Sorry for using language that offends you but that still does not make you right. The header of Table 1 in the article clearly shows that kH,cp is another name for k in the first section of the article (they both are partial pressure divided by concentration of the solved gas). Therefore, k must increase with temperature while you claim it should decrease. You do agree that partial pressure does, don't you? Certainly k is no measure of solubility It is diretly proportional to partial pressure. Your version of the van't Hoof formula would make partial pressure of gas dissolved in liquid decrease with temperature, after all. The version of the formula before my correction went against known laws of physics, common sense and even the formula in the next article section (\rho_m/\rho_g=e^{-\beta(\mu_{{\rm ex},m}-\mu_{{\rm ex},g})}\,). I will not state whose mistake it was, if you wish so, but the previous version of the formula was not correct. -Friendly Neighbour 20:47, 21 April 2007 (UTC)
OK, kH,cp = 1/kH,pc = 1/k. Now I see it. However, using the first is strongly misleading for a reader. Even a scholar, as you could see. I will correct it in the article. Sorry for my mistake. -Friendly Neighbour 20:53, 21 April 2007 (UTC)

I believe a section named "Other Forms of Henry's Law" should be self-contained as most readers will not be interested in more than one form. Therefore the next section should use the notation from the first section (namely k), not the "other" forms. I changed the temperature section accordingly. -Friendly Neighbour 21:32, 21 April 2007 (UTC)

Thanks for your apology and now we are at least on the same page. I am not sure that your re-wording is any clearer than it was before. In essence, you simply replaced k_{H,cp} with k_{H,pc} and that, indeed, justifies leaving the minus sign before the constant C in the equation for temperature dependence. That changed wording more or less says that k_{H,pc} is "the true" k. If you will read a number of the earlier comments and responses in this Talk page, you will see that there have been a number of people who disagreed with that and thought that one of the other forms was the "the true" k.
Be that as it may, I will only make some minor copy edits ... one of which is that the word "fizzy" is not needed. I don't think a physics or chemical engineering textbook would use that word. It may also confuse readers whose primary language is not English. In any event, we can now end this dialogue and thanks again for your apology. Regards, - mbeychok 22:11, 21 April 2007 (UTC)
Yes but k_{H,pc} is the "constant" (in fact it varies with temperature which makes the word a little unfounded) we use in thesection of the article where a reader should start: the first one. Therefore we should not change it into its inverse by ambush.
Fizzy. Well, are you quite sure "carbonated" is easier to understand for foreigners than "fizzy"? I'm not so sure. Actually, I was afraid "carbonated drink" may be too difficult for many foreign students who usually understand more colloquial English then "correct" English (influence of pop culture). But let it be carbonated, if you like. At least it is really the correct name. -Friendly Neighbour 22:41, 21 April 2007 (UTC)

All this arguing and the equation is still wrong! Probably the result of rogue editing. There should be a negative sign in front of the C if you are using the k_{H,pc} form, which goes up with increasing temperature. And there should not be a negative sign if you are using the k_{H,cp} form, which goes down with increasing temperature. This should be obvious to any engineer that actually puts this equation to use. —Preceding unsigned comment added by 198.180.131.21 (talk) 09:58, 23 February 2010 (UTC)

Reworked Henry's law vs Raoult's law[edit]

I've reworked this section after noticing that one particular sentence basically stated

The difference is that [...] kH is a value that differs from p*.

To be fair, the following sentence gave a reason but, while trying to merge the two sentences in an easy-to-read way, I thought of additions which required some rearrangement of the pre-existing content. It's pretty much all still there though, just in a slightly different form.

The final sentence about Gibbs-Duhem eqn. possibly still needs better wording, since it might be read as only applying to ideal-dilute solutions. Perhaps it does - the previous version made the same implication - but I've always preferred organic to physical chemistry so I don't know. - ObfuscatePenguin 10:18, 18 August 2007 (UTC)

Reasons for B class[edit]

An A class article is this :

Provides a well-written, reasonably clear and complete description of the topic, as described in How to write a great article. It should be of a length suitable for the subject, with a well-written introduction and an appropriate series of headings to break up the content. It should have sufficient external literature references, preferably from reliable, third-party published sources with a reputation for fact-checking and accuracy (peer-reviewed where appropriate). Should be well illustrated, with no copyright problems. At the stage where it could at least be considered for featured article status, corresponds to the "Wikipedia 1.0" standard.

Emphasis mine. I don't think its of potential Featured Article quality yet. Here's the things that needs to be improved to be considered an A-Class IMO:

  • An engaging lead, with perhaps a few historical details such as time of discovery, typical users of Henry's Law (which fields uses it, and examples of that use)
  • Fix appearance problems.
  • Some sections are in written in bold while they should not.
  • Use scientific or engineering notation rather than E notation (see Scientific and Engineering notation)
  • Properly seperate numbers (e.g., write 2,123.002 024 045 rather than 2123.002024045)
  • A picture would really add something to this article. Especially to the Temperature dependence of the Henry constant section.
  • Consider centering tables within the page.
  • Don't use "editorial" comments such as Note that, As discussed, ...
  • The "flow" could be improved. Many sections feels like simple stubs, and collection of stubs does not make an A-class articles.
  • Consider adding a atm <-> Pa conversion somewhere in there to tell the reader what exactly is an atmosphere.
  • Some sections are unreferenced. Namely:
  • Lead
  • Tables (perhaps the other sources give the values, in that case add inline citations next to the table titles)
  • Henry's law in geophysics
  • Henry's law versus Raoult's law
  • See also could perhaps be expanded, but I'm really not qualified to judge that one.

These needs to be addressed before it's considered A-Class IMO. Headbomb {— The greatest sin is willful ignorance.
ταλκ / κοντριβς/Projects of the Week
22:55, 15 June 2008 (UTC)


History of Henry's Law[edit]

I would like to have the historical background of Henry's Law, the Story of Henry's Law. What systems was it noticed in, that the early natural scientists, including Dalton and Henry, noticed some pattern? And how did they do the experiments to verify it? What boats got rocked by the promulgation of Henry's Law? Before any good theory gets traction, there was always some previous theory that was all nicely peer reviewed and solid as a rock. This becomes really interesting when it comes to, say, Henry's Law, because it isn't stated as a theory, it's the LAW. Richard8081 (talk) 00:13, 16 July 2008 (UTC)

Richard8081, I moved your comment about the History of Henry's law down here to keep the comments in chronological order. Yes, it might be interesting to include a section on the history of Henry's Law. If you could point me to a source of such information, I would write it up and add it to this article. Or you could do it yourself. - mbeychok (talk) 19:56, 16 July 2008 (UTC)

Problem "Because the pressure of CO2...CO2 comes out of solution as bubbles"[edit]

"Because the pressure of carbon dioxide above the liquid is now lower, some of the dissolved carbon dioxide comes out of solution as bubbles" The bubbles in the middle of the liquid cant know the carbon dioxide pressure = partial CO2 pressure. It can't see if it is a CO2 or just liquid all the way up.> Because the pressure above the liquid is now lower, some of the dissolved carbon dioxide comes out of solution as bubbles. don't take bubbles telepathy in account. —Preceding unsigned comment added by 89.1.4.108 (talk) 19:24, 12 February 2009 (UTC)

Sign of ΔsolvH[edit]

In the temperature dependence section, kH,pc is the equilibrium constant for the degassing process (vapor is the product). For this process, ΔdegasH = -ΔsolvH . Without the minus sign, it appears from the values given in the table that the solvation process is endothermic. This cannot be the case for gas molecules (almost no interaction) going into a liquid (strong interactions). Chrom69 (talk) 08:31, 28 April 2009 (UTC)

Dissolved CO2 reacts with water to form carbonic acid; therefore, this is not an example of Henry's law, as the solution-vapor equilibrium is mediated by a chemical reaction. —Preceding unsigned comment added by 72.241.178.158 (talk) 22:09, 3 May 2011 (UTC)

Hooray for us![edit]

This is a fine example of a scientific Wikipedia article.

The everyday example of carbonated drinks explains the concept in one paragraph for the non-scientist. Many other scientific articles could be greatly improved by adding similar examples before jumping into the science. Hooray for whoever added and worked on that paragraph! Earthlyreason (talk) 09:37, 20 May 2010 (UTC)

Volume of dissolved gas in a liter of water?[edit]

While researching possible improvements for Decompression sickness, I attempted to figure out the volume of gas contained in a human body at sea level. which led me to the question of the volume of gas contained in a liter of water at room temperature. In other words, if I extracted all of the dissolved gas in a liter of water and or a human body, how many liters of gas would that be?) Guy Macon (talk) 05:33, 9 May 2011 (UTC)

While you're researching all that about decompressions sickness and Henrys's Law could you keep a log of what you bump into and try to dope out whether that's how we stumbled upon Henry's Law in the first place, from guys getting the bends? Reading about the Brooklyn Bridge and caisson disease, you just know that the Romans must have tried to figure this out -- and failed to figure it out, I guess. Put it this way --- I'm real interested in Henry's Law because it explains why shake flasks of yeast, worldwide, are running at zero oxygen, even though the yeast geneticists are shakin'em boss, shakin'it (because Henry's Law is true at EQUILIBRIUM, and the oxygen is being sucked out of the system by the rapidly growing microorganisms. Duh.) So I figure some equally benighted form of knowledge gathering led to the observation about the behavior of gases dissolving into liquids that is embodied in Henry's Law. Richard8081 (talk) 11:23, 21 May 2011 (UTC)

www.henrys-law.org[edit]

FYI: This is my web page. It does indeed still exist. However, my internet provider seems to have problems and the page is occasionally down. I may have to switch the provider but the name www.henrys-law.org will stay the same.--RolfSander (talk) 07:50, 18 July 2012 (UTC)

Incorrect use of "solubility"?[edit]

I'm an animal physiologist, not a physicist, so I'm posing this to the regular contributors rather than making any changes myself. The fourth paragraph begins "An equivalent way of stating the law is that the *solubility* of a gas in a liquid is directly proportional to the pressure of the gas." (Emphasis mine.) Shouldn't that be *concentration*? The way I use the term solubility, it would be in units of mol/L·.atm. (Physiologists tend to use the form c = sp, where s is solubility, rather than p = kp.) Since s is constant if temperature and solvent don't change, it seems like the current statement is incorrect. AJC (talk) 15:32, 24 September 2012 (UTC)

If written as you propose:the solubility of a gas in a liquid is directly proportional to the concentration in the liquid, would that not be essentially equivalent to saying that the solubility of a gas in a liquid is directly proportional to its solubility ? Surely, that is not what you meant. mbeychok (talk) 20:03, 24 September 2012 (UTC)