# User talk:Petergans

## Activity in ternary solutions

Do you happen to know some sources containing tables with activity coefficients for ternary solutions like for instance sugar-salt-water?--188.26.22.131 (talk) 17:46, 18 February 2013 (UTC)

Sorry, I can't help with this request. Petergans (talk) 20:41, 18 February 2013 (UTC)

## Template:Did you know nominations/Vibronic spectroscopy

Petergans, I see it's been a while since you nominated an article for DYK. The nomination you just made simply doesn't qualify: it was new three months ago, and newly created articles are supposed to be nominated within five days. (Articles expanded 5x within the past five days are also eligible: again, it's newly expanded that's the key.)

Generally, if you're nominating, and your article can't accurately be placed in the "Current nominations" section of the page, it almost certainly isn't eligible. If you have to create your own date in the past, as you did, then it definitely won't be. BlueMoonset (talk) 10:43, 30 April 2013 (UTC)

Sorry about the delays. I had no idea there was a deadline until today, when I looked at the new "Your notifications" icon on the top line of my Wiki display and saw that you had mentioned me on BlueMoonset's user page which I have just read. I don't agree with the rule at all as I think that article quality is more important than speed of production. However we have to live with the rule that exists, so for the next time you want to submit to DYK I would say submit quickly and revise the article later. For Spectroscopic line shape, I probably will not do too much anyway as it is further from my interests and knowledge. Dirac66 (talk) 16:53, 1 May 2013 (UTC)

## DYK nomination of Spectroscopic line shape

Hello! Your submission of Spectroscopic line shape at the Did You Know nominations page has been reviewed, and some issues with it may need to be clarified. Please review the comment(s) underneath your nomination's entry and respond there as soon as possible. Thank you for contributing to Did You Know! RockMagnetist (talk) 15:58, 13 May 2013 (UTC)

## Raoult's law

Hi - could you glance at the latest edit of Raoult's law by 5.15.206.167? It seems confusing to me to use the same symbol for gas-phase fugacity coefficient and liquid-phase activity coefficient, but I am wondering if that is common in solution thermodynamics? Dirac66 (talk) 20:34, 23 May 2013 (UTC)

This article is a mess. It is written (badly!) in the style of "Wikipedia for Dummies". I suppose that because this topic is often taught at children there has to be some dumbing down, at least initially. I hate it when dumbing down means making erroneous statements. In this case, deviations from ideality are not just due to enthalpy effects (implied by talking about intermolecular forces); space-filling factors (entropy) also come into it. Deviations from ideality cannot be discussed at an elementary level.
My suggestion would be to separate the description of the law and deviations from ideality from the quantitative thermodynamics. Certainly fugacity, which has the dimension of pressure, and liquid-phase activity coefficients, which have no dimension, should be clearly distinguished from each other. According to Atkins, fugacity coefficient is given the symbol Φ, not γ. Petergans (talk) 07:32, 24 May 2013 (UTC)
Yes, I suppose you are right. I was not really looking at the article as a whole, but it does need extensive revision and should be reordered with the more elementary material first. And it should be done with extensive consultation of sources to ensure it is correct, as we did for the spectroscopy articles. I am not sure, though, that referring to intermolecular forces always implies that entropy effects are excluded. This is true if we consider only regular solutions, but stronger forces can produce ordering in solution.
Anyway, proper revision of this article would take more effort than I am willing to expend, so I have decided not to attempt it at least for now. Thanks for the discussion. Dirac66 (talk) 00:36, 25 May 2013 (UTC)

Hello wikifellows!

I've noticed the comments regarding the symbol of the coeficient of fugacity. I think that some details about the reasons for choosing a very similar notation are necessary.

Choosing the same letter and a subscript for distinguishing them is based on the need for notational uniformity requested by symbol overlaping which could appear in a broader context (for instance phi for fugacity coefficient, osmotic coefficient and volume fraction to mention just a letter which is involved in this discution).

The same letter also emphasizes the connexion between the two concepts and avoids the unnecesary overlap with distinct concepts like volume fraction. The subscript p comes from considering the fugacity coefficient as an activity coefficient in pressure like those based on dimensional expressions of compositions like gamma-c and gamma-b.

From the reasons shown above I suppose it is obvious that the chosen letter seems to be appropiate for the intended use.

A question arises in this context: On what is the statement concerning elementary non-approachability of the deviation from ideality based?--5.15.200.9 (talk) 21:57, 10 July 2013 (UTC)

## EDTA

At Talk:Ethylenediaminetetraacetic acid a request was made for formation constants for various metal ions. Seems like really useful idea and it also seems like the kind of info that you might have more available than the rest of us. If you lack the time, please suggest a source for me to consult. I noticed that there is a very full article on stability constants thanks to your major contributions, but even there one finds no list of data taht I could see. Thanks, --Smokefoot (talk) 17:22, 5 June 2013 (UTC)

I don't see the request. Anyway, there is a list of publicly available reviews in stability constants of complexes#Critically evaluated data. Petergans (talk) 17:57, 5 June 2013 (UTC)
Sorry to be of trouble. --Smokefoot (talk) 22:38, 5 June 2013 (UTC)

## Propagation of uncertainty

Hi Petergans, hi fellow chemistry lecturer

I saw you did some editing on the talk page of Propagation of uncertainty. I was reading that story and was struck by a remark in its early heading that propagated uncertainties can be used to formulate confidence margins. Optimistically it says something like: "if the resulting distribution is known or can be approximated". I think this is a little naughty to the point of deceptiveness. Say I have two measured quantities, say A=1.301(4) and B=1.10(5), both normally distributed. But I want to know f=ln(B)/A3. I can propagate error, but would you be mathematician enough to tell me how P is distributed? (I am not...). I think in general it is not possible to translate the propagated error into confidence and the article should say something about that.

What you cán do is generate a bunch of simulated A's and B's and calculate P's from them and look at the P distribution. A bit like bootstrapping, but not exactly the same. Looks pretty non-normal by the way. I doubt I am the first to do such a thing, but I am not sure where to find literature on that.

Any thoughts?

Jcwf (talk) 18:06, 26 June 2013 (UTC)

As you rightly point out, the probability distribution of products, quotients, etc. is not easy to derive from the distributions of the single variables. Linear combinations of variables only are discussed in Mardia, Kent, Bibby "Multivariate Analysis". This suggest that there is little or no literature on non-linear combinations. Petergans (talk) 19:04, 26 June 2013 (UTC)
Thanks!

Jcwf (talk) 19:41, 26 June 2013 (UTC)

## Activity standard state - another aspect

Do you happen to know some details about the choice of the pure solid as a reference state for activity coefficients in a mixture containing dissolved solid and subsequently about the activity of solvent (water) in moist solids?--188.26.22.131 (talk) 10:15, 3 July 2013 (UTC)

Simple answer: no. For multi-phase equilibria, the chemical potential approach is best. Petergans (talk) 10:40, 3 July 2013 (UTC)
Of course the chemical potential has been defined/devised in order to deal with phase (and chemical) equilibria. But isn't the activity involved in the expression of the chemical potential? The chemical potential approach reduces to the knowledge of activity coefficients.--188.26.22.131 (talk) 08:48, 15 July 2013 (UTC)

## WP:MEDMOS

Per the above we usually put further reading after the references section rather than before. Best Doc James (talk · contribs · email) (if I write on your page reply on mine) 07:50, 12 July 2013 (UTC)

## Quantitative description - ion association

Hi! I've noticed that you are the main contributor to ion association. I was wondering whether the phenomen could be described more quantitatively, in terms of perhaps degree of dissociation/association, van't Hoff factor, osmotic coefficient and the like.--188.26.22.131 (talk) 09:26, 24 July 2013 (UTC)

The quantitative aspect is the same as for any equilibrium constant.For ion pairs of the type A + B = AB, however, it is difficult to find a measurable quantity that allows the concentration of A, B, or AB to be obtained directly. Also, because A and B are ions, the ratio of total concentrations of A and B cannot be varied by simply adding A or B to a mixture; one must add AC or CB. Therefore there are few reliable equilibrium constants in the literature. Indirect methods based on measurements such as osmotic pressure, conductance, etc. have given wildly different values, summarized in Burgess's book.The reason for the discrepancies is that the calculations are model-based and in effect reflect different physical phenomena.Petergans (talk) 09:57, 27 July 2013 (UTC)
Thanks for the comments. There are some aspects which deserve further details to be specified in in the article.--188.26.22.131 (talk) 09:50, 31 July 2013 (UTC)
One of this aspects regards the quantities which can be related to the concentration of ternary ion associates. How could the concentration of this ternary associates be determined?
Other aspect concerns one of the assumptions used in a certain model-based calculation whose validity is questionable in general and especially in the context of concentrated solutions/ion association is that of total dissociation of the electrolyte. Can this supposition which is involved in some determination of the mean activity coefficient be one of the source of the inconsistencies mentioned and other inconsistencies regarding activity coefficient determined through various methods.--188.26.22.131 (talk) 12:43, 31 July 2013 (UTC)
My feeling is that these matters are too complicated to be included in this article. We did some work with the azide ion which showed spectroscopic evidence for the presence of triple ions (D.D.K Chingakule, P. Gans and J.B. Gill and P.J. Longdon, "Spectrochemistry of Solutions, Part 23. Changes of Enthalpy and Entropy in the Formation of Contact Ion Pairs: A Vibrational Spectroscopic Appraisal using Thiocyanate and Azide solutions". Monatsh., 1991, 123, 521-535. Azide is particularly well-adapted to form contact triple ions because both terminal N atoms are equivalent electron-pair donors. There is no adequate theory for concentrated solutions. Petergans (talk) 07:58, 1 August 2013 (UTC)
In cases like these matters a gradual and simplified approach is useful, by emphasizing the macroscopic aspects as well enumerating the possible hypotheses and tentative theories. Perhaps a comparison of concentrated solutions to ionic liquids and molten salts would be appropiate.--188.26.22.131 (talk) 14:36, 1 August 2013 (UTC)
The complexity of the situation is due perhaps to the number of simultaneous solvation and association equilibria involving triplets like

${\displaystyle \mathrm {AB+A^{+}\rightleftharpoons (AB)A^{+}} }$,

${\displaystyle \mathrm {AH+B^{+}\rightleftharpoons (AB)B^{+}} }$,

${\displaystyle \mathrm {(AB)A^{+}+sS\rightleftharpoons A^{+}(AB)S_{s}} }$

S the solvent, s solvation number.--188.26.22.131 (talk) 08:54, 2 August 2013 (UTC)

It's not a question of complexity, but paucity of direct experimental data with which the equilibrium constants can be determined. As I mentioned above, indirect data are extremely difficult to interpret. For example, there is a long-standing controversy about conductivity minima - do they imply the presence of triple ions or not?
This discussion does not belong this talk page. I don't see any way that the topic of triple ions can be elaborated further in the article. Petergans (talk) 10:04, 2 August 2013 (UTC)
I see, it is about competing hypotheses. The discussion could be moved to talk page of the article. Regarding the implication of ionic triples, what other alternative hypotheses are there?--188.26.22.131 (talk) 10:37, 2 August 2013 (UTC)

## Metal ions in aqueous solution - isotopic efffects

Noticing another article where you are the main contributor, I was wondering what can be said about the availability of data concerning properties (conductance, mobilities, etc) of metal ions in deuterated (and tritiated) water solutions.--188.26.22.131 (talk) 09:50, 31 July 2013 (UTC)

## Solvated electron

Could the solvated electron account for the difficulties in the theory of concentrated electrolyte solutions?

It seems odd that although the solvated electron has been detected, it is ignored in the relations of conductivities and electrode processes. Could it appear in formulas like Nernst equation?.

Being initial hypothesized in connection to alkali metal liquid ammonia solutions, what is the situation concerning alkali metal halides in liquid ammonia which have been mentioned in some reference from ion association? 188.26.22.131 (talk) 15:58, 1 August 2013 (UTC)

See solvated electron Petergans (talk) 20:16, 1 August 2013 (UTC)

## Feedback on talk pages

Hi Petergans! I've posted some comments on some talk pages like talk:Activity coefficient where your input is wellcomed.--188.26.22.131 (talk) 09:53, 19 August 2013 (UTC)

## C. W. Davies - notability

How do you regard the notability of the proponent of Davies equation? Should he have a wikipedia article? If you happen to know a source that mentions some info regarding the person, please point it out to me when you'll have time; I've tried Google search with not much succes in finding some info.--188.26.22.131 (talk) 12:46, 20 August 2013 (UTC)

## group 3 elements

Hello. I saw your extremely old comments on Talk:Yttrium advocating placing La below Y. I started a discussion at Wikipedia talk:WikiProject Elements#Should lanthanum be in group 3? that I'd like to invite you to participate in. ;-) (P.S. I'm still making up my mind on this. Currently I'm marginally favouring La below Y, but plan to read more on the matter first.) Double sharp (talk) 13:19, 31 October 2013 (UTC)

## Phosphate images

Further to our discussion on ProjectChem I see that you're going through the phosphates. I don't dispute that this needs doing, but the result (at the moment) is that you've removed nearly every image of a whole class of compounds. Can I ask if you intend to replace them with corrected images? Project Osprey (talk) 09:19, 21 November 2013 (UTC)

I've made sure that there are links to articles that have images of the anions. As to the structure of the salts, I am in correspondence with the Karsruhe people to try to get them give us access to their crystal structure database. First response was negative, unsurprisingly. Second response was better, they offered a subscription to me at the academic price. I'll give it one more try. Petergans (talk) 10:53, 21 November 2013 (UTC)

## Periodic table arrangements

"Standard" 18-column PT

As I see our conversation about the PT (on WT:CHEM and pointing to WT:ELEM), I think it's up to you to respond or follow up somehow. If you have more questions or thing you'd like clarified maybe I can help out. As a heads up, I can say that the discussion on group 3 and group 12 on WT:ELEM may lead to a conclusion (consensus) in this topic. -DePiep (talk) 07:41, 13 December 2013 (UTC)

The reason I asked for your help is that I would need the source code for creating a picture like this which has the desired structure. There is HTML code with the pages you indicate, but the tables there lack most of the lanthanides and completely lack groups 13-18. Please indicate where the code for the HTML table needed to create this picture can be found. I would be able to add element symbols to the source code and this will involve a lot less work than starting from scratch. Petergans (talk) 11:24, 13 December 2013 (UTC)
It is not in HTML unfortunately. It is .svg, which I edit offline with "inkscape" programme (there are more options). In short, SVG is an open standard (for Standard Vector Graphics), and uses XML.
If you want to play with PT structures and layout (not the typographical details), you can use simplified wikitable like Template:element cell-1 (copy the code /18-col or /32-col boilerplates to a page & edit the wikitable). Is what we do to keep talkpage WT:ELEM page thin and lean. Hope this answers. -DePiep (talk) 11:40, 13 December 2013 (UTC)
I have Inkscape and can handle XML. Petergans (talk) 13:55, 13 December 2013 (UTC)
Simple then. Just click the image here to go to the wp file page, then click on the image itself to see file-only (maybe need to go to commons?) and download/save the WP file via your browser! Note: if you change the PT structure, please upload as variant to a different name. Have a nice edit. -DePiep (talk) 14:32, 13 December 2013 (UTC)

The claims regarding IUPAC in our previous discussion appear to be dubious. Please look at http://iupac.org/publications/ci/2004/2601/2_holden.html. The table is published in the "red book". Note the IUPAC symbol in the corner of the table. Petergans (talk) 16:52, 13 December 2013 (UTC)

Periodic table is discussed at WT:ELEM. -DePiep (talk) 17:46, 13 December 2013 (UTC)

That’s a very disappointing response. This is not personal. Rather, it highlights a central weakness in Wikipedia, namely the concept of consensus applying only to Wikipedia editors. This is why I’m having so much difficulty getting my point across. I’m looking at it from a more general perspective; familiarity is very important, like the wall charts at Amazon which you posted a comment on.

The main purpose of showing a PT in the infobox is to show the place of an element in the PT. A familiar layout helps in this regard.. I would prefer to see a PT without additional information, such as atomic number and mass, which can be displayed explicitly in the infobox.

Classification will always vary according to the chosen criteria. Many elements belong to more than one category. If any classification is to be shown in the infobox there needs to be a legend explaining the basis of the classification (no legend at the present time).

Following the thread of this logic my suggestion for a PT in the infobox would be as follows. It is based on a common-sense interpretation of the IUPAC table. Obviously the particular element should be highlighted in some way. I don’t know how to do that. Will you help me to realize this proposal? I followed your suggestions but could not find any source code.

 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La (58-71) Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac (90-103) Rf Db Sg Bh Hs Mt Ds Rg Cn Fl Lv 58-71: Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 90-103: Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
OK, you deserve an answer here.
Beforehand I say this: I understood already that it is not personal. I will reflect what is discussed at WT:ELEM (I've spend hours there), and maybe what opinions are (including mine) - separately. When it is about helping (explaining or describing): no problem. Also, if the general conclusion would be against my opinion, I have & will loyally put that outcome in the articles (for example, I deleted the Bohrian electron shell images (the circles) from the infoboxes -- while I made many of them ;-) ). I'm not a chemist or physicist, so I had to study the topics since a few years. But for conclusions and changes in articles, I must & will point to WT:ELEM talkpage, because it must be central. So not WT:CHEM either.
Please be prepared that this is an old and complicated topic (complicated as in: "many issues involved"; not "esoteric"), also in RL. (Of cvourse you are, but there is a lot of link following and shortcut words involved) -DePiep (talk) 12:50, 14 December 2013 (UTC)
Description of the topic. First, what it is not:
We are talking about the structure of the PT. Not about typography ("nice asterisk"). Also, I state here & now that the 18-column and the 32-column PT must be consistent. Cut & paste of elements is not relevant: they must be a description of the same. This is why I also reject any 18-column PT that is not clear about how & where the below-elements are to be inserted in above (many published PTs have this bad ambiguity, e.g. do Sc and Y span the whole f-block? -- btw your demo Pgans-1 above is correctly unambiguous in this. Except: the positioning of group number "3" could become an issue ...).
We want that single, consistent 18/32 column PT form for all over en:wikipedia. Next to that, all structural variants (e.g., different group 3 setups) must be & can be described in relevant topical pages (like in group 3 elements, scandium, ytterbium, lanthanides, or Periodic table group 3 variants, Janet left step).
I am not happy with the qualification "standard" PT. We all know that there is no "standard" one. I better not use it, it suggests a preference (worldwide, not just in WP). Bad word.
If you disagree so far, better say so right away.
I can now zoom into our topic:
About your IUPAC link Holden, Coplen (2004). I reject that PT (the one with the blue & yellow markings). Because: it leaves undecided where Sc and Y go when the below-area is placed back into the PT (to make the 32-col PT). Also, that PT has no group numbers! (how should the reader find that out?).
The paper is great reading though, and nicely puts the development in sequence (with years mentioned). You'll agree that it is mostly about backgrounds of Ln and An sets, and the very heavy elements. These topics are now stable I dare saying. But it is not exact or conclusive on the group 3 arrangement.
I also reject our current PT presentation (the very image you have put here, also {{Periodic table}}) for the same reason: ambiguous Sc & Y positioning, and the groups [blank]+3 arrangement. Structural flaws, leaving the reader with an ambiguous PT, still not clear when the poor reader would do a lot of research homework.
So I supported (at WT:ELEM) the proposal that said: we choose one group-3/group-blank definition for out main PT presentation. I then introduced a "gap" to show this in the 18-column PT. My gap is in {{Periodic table/sandbox}}. The gap should prevent any confusion for an 18-to-32 column transformation, and back. Note that the /sandbox also solves the Lanthanide–Rare earth metal–Transition metal questions (actually by leaving out Ln naming). This Ln/REM topic I'll not develop here. Another consequence is that we are free to choose the below-block (eg, put Lu, La below or in-above?), as long as it follows the (group 3) definition chosen. So, the gap is there to stay, for me.
You have use a gap too above in Pgans-1, but with a different group-3 definition. We both see the advantages of a gap (even over Holden/Coplen)! Let's keep one.
So far, I think we are converging to the detail of our issue. Namely: how to define and position the group-3 plus group-blank elements. From here, we both think different. -DePiep (talk) 13:54, 14 December 2013 (UTC)
About group-3 definitions, and group-blank. Eric Scerri wrote this in 2012.
He arrives at acceptable variants, scientifically based:
Scerri figure 4: group 3 = Sc/Y/Lu/Lr; to the right of f-block
Scerri figure 5: group 3 = Sc/Y/La/Ac; to the right of f-block
Scerri figure 6: group 3 (?) = Lu/Lr; Sc/Y glued right next to group 2;
Pgans-1 is Scerri figure 6 (!). (Please add a "3" to your PT). I will put that one below (in 32-col form). It was already discussed on the talkpage since October 31 ;-), we did not hide it. I hope we agree that from these three, there is not one single correct one: there are three. IUPAC has not chosen a "best" one either, today.
From these three, this is the line of reasoning in the current WT:ELEM proposal.
A. There is no single one "good" or "standard" PT structure in this. There is not one single IUPAC approved PT today.
B. We are free to pick one at WP, provided that we describe & source it. This is not OR (we are not inventing a PT).
C. Proposed is to choose Scerri figure 4.
D. This also allows a correct presentation of the Lanthanides/REMs/Transtion metals question (categorizing and coloring); a parallel issue.
E. Variants (including Scerri 5, 6) are to be described in appropriate places (group 3 element already has a start).
Personally I think that we can not present all three variants in one general PT. That would be too much detail & distraction; graphically irresponsible.
The consistent proposal also trumps many published PTs (wallpapers, books) that are unclear about this group 3. We are not here to republish sourced vagueness.
So this is the main line, with the proposed outcome. The argumentation for "choosing but not declaring the sole one" is on WT:ELEM, I find it difficult to repeat here. The proposal has both 18-column and 32-column demos, consistent of course.
Up to you. I tried to explain how the choice proposal for one is build up (and it drops our current PT, another unclear one; the image above). It is not a clean cut outcome, we all know, but it has the strongest arguments for it (as I understand it). Your variant must be & will be described, more elaborately than today, in the topical pages; I expect there will be a good graphic available too (I actually plan to make one, when an outcome is settled). I do defend the procedure to have your proposal weighed (well, it was already in there), but I can not defend your proposal because I reached an other conclusion.
If you still think your/Scerri's other PT structure should be presented in general (and the current proposal be moved to topic pages only), it is up to you to argue for it at WT:ELEM. At least do cast a vote, even with only short arguments or a link here to your earlier arguments). Editors there are more into the PT science than I am. And I know the other editors there are very, very sincere in responding to objections as serious as you have. -DePiep (talk) 15:19, 14 December 2013 (UTC)
As for your time restrictions. I'm not sure if the large discussion there will close within next week. At least you should drop a quick vote there with a beginning of argument, asap. -DePiep (talk) 16:13, 14 December 2013 (UTC)
Just one quick comment before I go. The assertion that the * notation is ambiguous cannot go unchallenged.. * is simply a place-holder It signifies that the row of elements marked * (below) should be inserted here, in place of the *. There is no other way to interpret it. Petergans (talk) 19:19, 14 December 2013 (UTC)
Yes. But in some PTs such a replacement (from below into the PT, at * place) is ambiguous. A PT is not always clear about what happens with Sc and Y, when they get 14/15 cells added below. Example: the image used here. Have a nice time, see you later. There is time. -DePiep (talk) 20:23, 14 December 2013 (UTC)

## Scerri figure 6

Eric Scerri, 2012. Equals demo Pganbs-1 above. "Group 3" number is added.

Periodic table, variant Eric Scerri (2012) figure 6
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1 H He
2 Li Be B C N O F Ne
3 Na Mg Al Si P S Cl Ar
4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
6 Cs Ba La * Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
7 Fr Ra Ac ** Rf Db Sg Bh Hs Mt Ds Rg Cn 113 Fl 115 Lv 117 118
* Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
** Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Added to WT:ELEM by Double sharp (talk) 15:28, 30 October 2013 (UTC) Copied here -DePiep (talk) 15:19, 14 December 2013 (UTC)

Happy New Year to all

De Piep: I think you misunderstand my intentions. I want to put a proposal up for discussion in the wider community. I would like to present a clear choice along the lines of (crudely)

The essence of my proposal will be

• Element names in their respective boxes, with actual element highlighted.
• No atomic number or atomic mass
• No colour coding of element boxes
• No before and after side-bars
• No links to other elements
 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La * Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac ** Rf Db Sg Bh Hs Mt Ds Rg Cn Fl Lv *: Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu **: Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

I do not have the capability to create this kind of graphic. All I can do is produce it as a wikitable like my preferred one, above. That's why I have asked for your help.

I want to propose a familiar form of the periodic table whose sole function is to show the position of an element within it. Properties, such as atomic number and atomic mass, are listed as separate items in the chembox and don't need to be duplicated. All discussion about which group an element belongs to etc., which may or may not be controversial, belongs elsewhere in the chembox, or the body of the article. Petergans (talk) 18:04, 1 January 2014 (UTC)

About PT structure & content (the science). You propose column Sc/Y/La/Ac. That is in the group 3 discussion at WT:ELEMENTS. The discussion is still open, and you and WP:CHEM were invited long ago. A core of that discussion I have written here above. But no way I will support any fork of that discussion. (still, as I said at WT:ELEM, if such a structure is the outcome of the discussion, or it is needed somewhere to illustrate a point, I'll be happy to make it).
About the formatting/tablelayout you propose. I see no advantage in 1. unclickable elements, 2. omitting group numbers and period numbers, 3. omitting the unnamed elements (like element 113).
None of these two topics you mention here are proposed at WT:ELEM. If you have a special usage for this one (both structure and format), please point to the page and the topic for any usefullness. As is said in the WT:ELEM discussion, within a topic anything is possible to explain something (see for example Chemical_element#Abundance). But not for the vanilla PT we use. -DePiep (talk) 12:15, 3 January 2014 (UTC)
Adding. Above I pointed to Template:Periodic table (nutritional elements). That was to illustrate that we can mark any specific grouping of elements, related to a topic. I just noticed that that PT has a Sc/Y/La/Ac column (and no group, period numbers). That aspect I did not want to illustrate. If and when the content discussion at WT:ELEM about group 3 is closed as proposed, that PT structure will be changed into a vanilla PT. (A Sc/Y/La/Ac column can be present in a PT in an article section where that variant is described). -DePiep (talk) 14:51, 3 January 2014 (UTC)

### One question

Why not show the unnamed elements 113, 115, 117, and 118 on the table? Double sharp (talk) 08:46, 20 January 2014 (UTC)

## Cardinal cubic B-spline

Hi Petergans,

the file http://en.wikipedia.org/wiki/File:Cardinal_cubic_B-spline2.png shows a cardinal cubic B-spline with a maximum value of 4 at its center. To my understanding the maximum value should be 2/3. But as I'm new to splines I'm not sure about it. — Preceding unsigned comment added by 78.43.252.123 (talk) 21:04, 1 February 2014 (UTC)

## Leeds meetup

Hi Peter, the second Leeds meetup will be held on 15 March - see here. Hope to see you there, Bazonka (talk) 21:15, 24 February 2014 (UTC)

## Pitzer ion interaction

Thanks for your feedback on Pitzer ion interaction I have WP:PRODed the article. ~KvnG 21:27, 7 March 2014 (UTC)

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## Calculation of the Ka value

Hi Petergans,

The question is about the calculation of the Ka value. For example:

Ka(H2O) = [OH−]×[H+]÷[H2O]
= (Density(OH−)÷Molar mass(OH−))×(Density(H+)÷Molar mass(H+))÷(Density(H2O)÷Molar mass(H2O))
≈ (?g/L÷17.01g/mol)×(?g/L÷1.01g/mol)÷(999.97g/L÷18.01g/mol)
≈ ?mol/L×?mol/L÷55.52mol/L


But how to get the Density(OH
) and Density(H+
)? Or is it possible to get the [OH
] and [H+
] directly?

Thanks. 123.119.16.126 (talk) 13:58, 27 May 2014 (UTC)

Of course one cannot determine the density of single ions. In equilibrium expresions [x] means "the concentration of x". Usually the concentration is expressed in units like moles per cubic decimetre. The use of concentrations is an approximation. Strictly speaking an equilibrium constant is a quotient of activities and therefore has no dimension. Petergans (talk) 08:41, 28 May 2014 (UTC)

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## Acid dissociation constant - graph error

Hi. A numbered user has spotted an error in one of your graphs from 2008. See Talk:Acid dissociation constant#pH/pKa inconsistency in phosphoric acid. Perhaps you still have the original spreadsheet and can just change one incorrect value (of Ka1?) to generate a corrected graph? Dirac66 (talk) 03:21, 26 September 2014 (UTC)

## File:Weak acid titration curves.png listed for deletion

A file that you uploaded or altered, File:Weak acid titration curves.png, has been listed at Wikipedia:Files for deletion. Please see the discussion to see why it has been listed (you may have to search for the title of the image to find its entry). Feel free to add your opinion on the matter below the nomination. Thank you. Arthunter (talk) 16:43, 20 November 2014 (UTC)

## Acid dissociation constant

Would you mind explaining why you reverted me here? I don't see why my edit was wrong. ekips39❀talk 21:21, 5 June 2015 (UTC)

In UK English usage an is used before a vowel or the letter h. Is it different in US usage? c.f. anharmonic, asexual ... Petergans (talk) 09:07, 6 June 2015 (UTC)

## Buffer solution

Hi! I see you're one of the major contributors to Buffer solution and author of File:Buffer_titration.png, and undid my revision containing the new graphic. I see the original image was being vandalised by Mediawiki's SVG library -- I rectified this and undid your revision. Is the image correctly corresponding to the source material? If not, let me know and I'll correct. Thanks for your contribution. Lasse Havelund (p · t · c) 18:24, 27 July 2015 (UTC)

## Speedy deletion nomination of Metal Ions in Life Sciences

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## Nomination of Metal Ions in Life Sciences for deletion

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## Structure of electrolytic Solutions - 1959 book

Hello, Petergans! I want to ask seeing your various edits re electrolytes and chemical thermodynamics whether the full text of the source Structure of electrolytic Solutions - editor W. J. Hamer cited on activity coefficient#Concentrated solutions of electrolytes is accessible to you (perhaps at your institution's library)? Thanks.--82.137.9.95 (talk) 15:39, 15 September 2016 (UTC)

No, it is not Petergans (talk) 08:41, 16 September 2016 (UTC)

## Data source for hydrolysis graphs

Do you have a cite for these graphs:

I'd love to have higher quality graphs (I can generate them if I had a data source) and/or get them onto commons for wider availability, but we need some reference for the underlying science first. DMacks (talk) 05:12, 25 November 2016 (UTC)

I created these graphs using my program HySS, which is available as freeware at http://www.hyperquad.co.uk/hyss.htm . There is a link to the publication that describes the chemical and mathematical basis of the program on the that page. I still have the source code. Vector graphics were used to create the images, so that they are scalable. Any suggestions for improvement will be welcome. Please contact me by e-mail (address on the Hyperquad web-site). I can then send you the data files that were used to create the diagrams. Alternatively I can send the numerical data from which the diagrams can be created.Petergans (talk) 11:49, 25 November 2016 (UTC)

## Acidity and basicity constants for metal hydroxides

Hi. I would be interested in your comments on my recent post at Talk:Acid dissociation constant#Basicity and acidity constants in infoboxes for metal hydroxides ?. Dirac66 (talk) 23:54, 18 December 2016 (UTC)

## Merger discussion for Inorganic anhydride

An article that you have been involved in editing—Inorganic anhydride—has been proposed for merging with another article. If you are interested, please participate in the merger discussion. Thank you. --HighFlyingFish (talk) 23:15, 16 June 2017 (UTC)

## Equilibrium Constant

Hi Petergans,

Thanks for the courteous message. I was on the fence regarding whether it is necessary to define reaction quotient. In the end I gave a simplified definition in the first paragraph for the sake of completeness (just as I gave a one sentence definition of what equilibrium means.)

I felt that it is for the benefit of novice readers (with only a rudimentary knowledge of chemistry) to at least know that the reaction quotient is a number varying over time that depends on concentration values. Otherwise, the whole article is incomprehensible, unless they read the reaction quotient page in some detail.

I think if you can further simplify the intro paragraph, please do so, but at least a vague description of what a reaction quotient is should be given.

Alsosaid1987 (talk) 16:27, 19 November 2017 (UTC)

Hi Petergans:

I'm afraid I have to disagree with your viewpoint in this. I understand what dynamic equilibrium means, and I'm afraid you are the one who has a misconception. If you look at the overall rate constant at which a reaction reaches equilibrium (assuming first-order in both directions), it is (k+k'), and thus, equilibrium is reached via first order decay (i.e., e^(-(k+k')t)). Mathematically speaking, this never reaches 0, and this point was emphasized by R. G. Bergman in his lectures at UC Berkeley. Of course, there is a point at which instrumentation is no longer able to detect any changes, and for practical purposes, a reaction is considered to be complete after 5 half-lives.

This is not dumbing down. I edited the previous version, because some definitions (specifically Kc) contradicted the IUPAC Green and Gold book's definitions. (Being mathematically inclined, I could not tolerate the errors in dimensionality.) Also, I specifically emphasized that for practical systems studied in the laboratory, the time to reach equilibrium is indeed finite for all intents and purposes.

I edited the previous version of this article due to numerous inaccuracies. I am striving for readability in the intro and accuracy in the main body.

Please do not revert just because you found one objectionable statement. Edit!

By the way, I am perhaps not as senior as you are, but I am also an expert in the field as Assistant Professor of Chemistry at the University of Pittsburgh, having previously completed graduate and postdoctoral training at UC Berkeley and MIT, respectively.

Alsosaid1987 (talk) 16:26, 20 November 2017 (UTC)

150.212.127.88 (talk) 15:51, 20 November 2017 (UTC)

Hi Petergans,

Just to remind you of the mathematics of the kinetics of an equilibrating system: Consider A<->B with forward and backward rate constants k and k'. And let x=[A]_0-[A]. Then we can write the differential rate law as dx/dt=k([A]_0-x)-k'([B]_0+x). It's not hard to show from there that the integrated rate law is ln((k[A]_0-k'[B]_0)/(k[A]_0-k'[B]_0-(k+k')x))=(k+k')t. Now let x_eq=[A]_0-[A]_eq. At equilibrium dx/dt=0, so the differential rate law gives k[A]_0-k'[B]_0=(k+k')x_eq. Substituting into the integrated rate law gives our final result: [A]-[A]_eq=([A]_0-[A]_eq)e^(-(k+k')t).

This is a result that is quoted in works like Anslyn and Dougherty's Modern Physical Organic Chemistry. Thus, if you accept the view that it takes an indefinite number of half-lives for a radioactive element to decay to nothing, then this is the same. Of course, in real life, if one starts with a mole, then after log_2(N_A * 1 mol) or approximately 79 half-lives, then one would expect only a single atom to be left. The idea of a half-life is not really meant to be applied to a single particle (it could decay in the next moment, or it could last forever). I don't really want to discuss the philosophy... Perhaps "infinite" is a slightly misleading term, but one cannot give a definitive time at which the process is "over". I hope this clarifies things!

Best, Alsosaid1987 (talk) 05:13, 24 November 2017 (UTC) 67.186.58.77 (talk) 05:12, 24 November 2017 (UTC)

Hi Petergans,

For the equilibrium constant article, I have rewritten the first part of the basic definitions and properties section (with the IUPAC gold book as a guide). Hopefully, this rewritten form should address your concerns.

Best, Alsosaid1987 (talk) 07:41, 24 November 2017 (UTC)

Hi Petergans,

I would also like to get a sense of why we are in disagreement. There may indeed be a difference between solution and gas phase equilibria, but I think there may be some more fundamental disagreements.

I, as well as the Chem Ed NZ article, derived the kinetics of A<->B type equilibria. I don't think you dispute the fact that mathematically, the result is that equilibrium is approached via exponential decay. I infer that you believe at a certain point, this equation no longer reflects what's going on inside the reaction flask. So I ask you, at what point do you think the exponential approach to equilibrium concentrations breaks down, and for what reason. I would also kindly ask you to provide a source. Note that just because several textbooks you consulted did not explicitly address this question of "how long does it take to reach equilibrium", that does not imply that these textbooks endorse your view that equilibrium is reached at a definitive time.

Secondly, I realize that not all sources state the same (see below), but the IUPAC explicitly states that K_c has units of concentration to the negative power of the particle number change. This is stated on pg. 73 of the Green Book. I do not disagree that for the purposes of Delta G = -RT ln K, one must use a dimensionless version of K. However, that is the purpose of the activity-based thermodynamic equilibrium constant. This is also why we must careful distinguish the concentration, partial pressure, and thermodynamic equilibrium constants. According to the IUPAC, they do not have the same dimensions, and only the last one is unitless by definition.

Note that your current definition of K_c is inconsistent. You describe K_c as K times a quotient of activity coefficients. However, at the same time you state that K_c is a quotient of concentrations. Because activity coefficients are all unitless, these two statements cannot both hold, and that is why I tagged them as inconsistent.

I note that Atkins and dePaula indeed define K_c to be unitless, by defining it such that all concentrations are first divided through by the standard concentration of 1 mol/L, so that numbers going into the quotient all all unitless. However, that is not the IUPAC's definition.

I hope you carefully consider and address these points.

Happy Christmas,

Alsosaid1987 (talk) 19:23, 25 December 2017 (UTC)

I don't disagree with the kinetic approach. The point of disagreement is with the speed of reaction. When determining equilibrium constants the data are obtained by means of a (generalized) acid/base titration. Most reactions are extremely fast; one waits only a few seconds between titrant additions.§ Some reactions are noticeably slower, e.g. Ca,Mg with EDTA, but still not requiring more than a minute or so between additions. Incidentally, regarding gas-phase reactions such as the synthesis of ammonia, for the purposes of this article one must assume that a catalyst is present, if needed, to attain equilibrium in a reasonable time. § Most determinations these days are done with autotitators which measure the rate of change of pH after a titrant addition and trigger the addition of more titrant when the rate falls below a predetermined value. Petergans (talk) 20:47, 25 December 2017 (UTC)

Petergans (talk) 20:47, 25 December 2017 (UTC)

## Excess chemical Potential and electrochemical potential

Hi, I posed a question on in the Wikipedia but there seems to be no expert around who could answer my questions. You appear to me as the expert I want to consult in this question :)

How are the Excess chemical Potential and electrochemical potential related. Let s say I have a solution of Ions of given concentration. Then for every type of Ion, I may provide an excess chemical potential. This excess chemical potential tells me how much e.g. the electrostatic interaction (between the Ions) alters the ideal chemical potential of that kind of ion type. If I write down the Free enthalpy of the system ${\displaystyle G=U-TS+pV=\sum _{i}\mu _{i}N_{i}}$ will I have to add an additional term for the electric potential(${\displaystyle +\sum _{i}z_{i}F\Phi \cdot N_{i}}$) or is it sufficient to write ${\displaystyle \mu _{i}=\mu _{i,ideal}+\mu _{i,excess}}$ ? If the last thing is sufficient, when will I need to add the extra term for the electric potential to the free enthalpy ${\displaystyle G=U-TS+pV=\sum _{i}(\mu _{i}+z_{i}F\Phi )N_{i}}$, where ${\displaystyle {\overline {\mu }}:=(\mu _{i}+z_{i}F\Phi )}$ is the electrochemical potential. Or will the electrochemical potential just give me ${\displaystyle \mu _{i}=\mu _{i,ideal}+\mu _{i,excess}}$? I would really, really appreciate your help and would hope that wikipedia explains this to it s readers. Kind Regards! --129.69.120.91 19:16, 16. Apr. 2018 (CEST) — Preceding unsigned comment added by 129.69.120.91 (talk) 12:13, 3 May 2018 (UTC)

Sorry, I can't help. My specialty is inorganic chemistry, not physical. Petergans (talk) 18:53, 3 May 2018 (UTC)
Do you have an idea, whom I could ask? :) --129.69.120.91 (talk) 19:47, 3 May 2018 (UTC)
This is a very specialized question. I suggest you approach a University professor, but I fear that he will only point you to an advanced textbook. Petergans (talk) 07:35, 4 May 2018 (UTC)