# Talk:Compressibility factor (gases)/Draft

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 Definition:  A thermodynamic property for modifying the ideal gas law to account for behavior of real gases. [d] [e]

## There is an article of the same name on Wikipedia

Despite the same name, this article was written completely from scratch. Any similarity with the WP article is purely coincidental. - Milton Beychok 21:15, 2 April 2008 (CDT)

## EOS

Milton, would it be possible to sketch briefly the pros and cons of the different EOS's? I finished reading and I'm ready to approve the article. --Paul Wormer 12:50, 5 April 2008 (CDT)

Paul, thanks very much for findimg all those typos and for adding a few bits information as well. I must have read it a dozen times and I still had some typos!! I would still like to wait, at least a week for other editors (if any) who may have comments, before you nominate the article for approval.
As for a comparison of the EOS's, I tried that when I was writing the article but couldn't come up with anything that I liked. Some are better in certain areas but not as good in certain other areas. So I decided to say no more than the following (in the section on "Modified versions of the van der Waals equation"):
Perhaps the most commonly used equations of state by engineers working in petroleum refining, petrochemical production, natural gas processing, cryogenic distillation and related industries are: the Redlich-Kwong equation developed in 1949, the Soave-Redlich-Kwong equation developed in 1972 and the Peng-Robinson equation developed in 1976. Those three equations are essentially modified versions of the van der Waals equation.
If you have some wording to suggest other the above, I would be pleased to have you send it to me. Milton Beychok 21:15, 5 April 2008 (CDT)

## Notation of powers

You write $T^{2.5}, \quad T^{0.5}$ instead of $T^2 \sqrt{T}$, and $\quad \sqrt{T}.$ The first notation implies that other powers are OK too, say T2.6, but I can imagine that dimensionality arguments only allow exact square roots. If that is the case then the second notation is preferable. If the exponents (2.5 and 0.5) are more or less coincidental (i.e., give best fits) then the first notation is preferable, but a remark about this would be in order. --Paul Wormer 13:31, 14 April 2008 (CDT)

Paul, thanks for your comment and it is good to hear from you again. I will change the notation to $T^2 \sqrt{T}$ and $\quad \sqrt{T}$, if you so wish.
But I honestly don't see the difference. My calculator gives me the same numerical answer for either notation.
Perhaps, some readers might possibly imply that $T^{2.5}$ means other powers are okay also. However, if they use the equation as written (without pondering any implications), they will get the correct numerical answer.
I referenced those Redlich-Kwong equations to Chapter 3 of Ji Lin Wang's doctorate thesis (reference 19) and to Jean Vidal's book (reference 20). Wang wrote the equations exactly as I did and, on page 114 of his book, Vidal used $T^{2.5}$ also just as I did. However, be that as it may, I repeat that I will change the notation to $T^2 \sqrt{T}$ and $\quad \sqrt{T}$, if you so wish. Just let me know. Regards, - Milton Beychok 15:53, 14 April 2008 (CDT)
You are an engineer, that is clear. As I said above, for a physicist/mathematican T0.5 has a different connotation than $\scriptstyle \sqrt{T}$. You will be surprised, but T1/2 and T5/2 are OK, too. To me the decimal notation implies 2 significant digits and not an exact value.--Paul Wormer 16:18, 14 April 2008 (CDT)
Okay, I have made the pertinent changes using T1/2 and T5/2. If I missed any occurrences, please let me know. As I said elsewhere, we must all learn to understand the other's common usages or conventions. - Milton Beychok 17:48, 14 April 2008 (CDT)

## Approval

I added chemistry as cat, else I cannot approve it, and approved it.--Paul Wormer 17:54, 14 April 2008 (CDT)

Hi All, in reviewing the mechanics for nomination for approval, I look to see if the nominating editor has made any content edits (copyedits are fine). I noticed these two edits by Paul that appear to be content related. What that means is that I either need two more editors to agree to the nomination, or Paul may remove the information. If someone else would like to re-use that same information, that would also be fine, but the idea is not to be able to approve your own work. Let me know if you have any questions. --D. Matt Innis 07:33, 15 April 2008 (CDT)
These two additions are so minor that I had forgotten about them.On the other hand, I didn't put them there for the fun of it and so I hesitate to retract them. I could delete them and Milton could reinsert them, would that be OK?--Paul Wormer 09:35, 15 April 2008 (CDT)
Matt did say "... or Paul may remove the information. If someone else would like to re-use that same information, that would also be fine ...". So why don't you go ahead and delete your edits and I will reinsert them, as you suggested. - Milton Beychok 19:02, 15 April 2008 (CDT)
Technically, if Paul takes it out, Milton doesn't have to put it back in if he doesn't agree with it. If he does put it back in, then that would be just as if you two had agreed here on the talk page, so that would be fine with me and should satisfy any requirements that I am obligated to follow. --D. Matt Innis 19:14, 15 April 2008 (CDT)

## Removal

I removed from the section on the virial expansion:

A statistical-mechanical expression for B was first derived by Ornstein in his Ph.D Thesis.[1]

and from the van der Waals equation:

they are, however, independent of P, V and T. In other words, they are constant for the gas being considered.

--Paul Wormer 19:30, 15 April 2008 (CDT)

I have reinstated the above two deletions. Met vriendelijk groet, - Milton Beychok 01:10, 16 April 2008 (CDT)
I forgot to translate the title of Ornstein's thesis: Application of the statistical mechanics of Gibbs on molecular-theoretical problems. Maybe you can add this in brackets? --Paul Wormer 09:33, 16 April 2008 (CDT)
Done. - Milton Beychok 10:49, 16 April 2008 (CDT)

## APPROVED Version 1.0

Congratualtions! Is this the first of the Chemical Engineering subgroup.. Good job! --D. Matt Innis 19:00, 21 April 2008 (CDT)

1. S. L. Ornstein (1908) Toepassing der statistische mechanica van Gibbs op molekulair-theoretische vraagstukken, Leiden