User talk:Retired Pchem Prof/JouleThomson

Derivation of the Joule-Thomson coefficient

Style

There is an important guidance document at Wikipedia that describes all the things that Wikipedia isn't. See Wikipedia:What Wikipedia is not. At para 2.7 it states that Wikipedia is not a manual, guide book or text book. Consequently high-quality articles should not use the first-person plural ("we") in the manner to be found in a good textbook. In your draft there are six instances where you are proposing expressions with "we" such as That is what we will do in this section. This mode of expression would be commendable in a textbook, but Wikipedia isn't a textbook. I suggest you find alternative language, more appropriate to an encyclopaedia.

• There is a sentence "... it is possible to derive relationships between and other, more convenient quantities." There appears to be a missing word after "between".

• The final sentence begins "The provides an expression for the Joule–Thomson coefficient ... ..." There appears to be a missing word at "The xxxxx provides an expression ....

Dolphin (t) 09:15, 21 January 2016 (UTC)

Thank you, Dolphin. I have now banished we, regrettably with some increased use of the passive voice. I have also made the other corrections. I hope you don't mind my moving things around; I am still figuring our how to organize things here. @Dolphin51: Retired Pchem Prof (talk) 23:32, 21 January 2016 (UTC)

Equations

You are proposing:

$\mu _{\mathrm {T} }=-C_{\mathrm {p} }\mu _{\mathrm {JT} }$ .

"This equation can be used to obtain Joule-Thompson coefficient from the more easily measured isothermal Joule–Thomson coefficient."

Your equation is written in the form that can be used to obtain the isothermal J-T coefficient when C_p and the J-T coefficient are known. If you wish to present an equation that can be used to obtain the J-T coefficient when the isothermal J-T coefficient is known, I suggest the equation should be presented as follows:

$\mu _{\mathrm {JT} }=-{\frac {\mu _{\mathrm {T} }}{C_{p}}}$

Dolphin (t) 12:10, 23 January 2016 (UTC)

Done. Retired Pchem Prof (talk) 20:41, 23 January 2016 (UTC)

Sources

I have now worked through the proposed section and it looks to be satisfactory. Do you have suitable source documents to identify in in-line citations to allow independent verification of the working? When suitable in-line citations are available I have no objection to the new section being pasted into Joule-Thomson effect. Dolphin (t) 11:56, 24 January 2016 (UTC)

I am puzzled by what you mean by "citations to allow independent verification of the working". Anyone who can follow the math can verify it. The techniques are standard; I provided links to other articles for two of them (cyclic rule, Maxwell relation) and the third (dividing through) is "obvious" (not really, but it is usually presented just this way in textbooks and someone with enough math to spot it as cheat can probably do it the rigorous way; I could not find that done in the other thermo articles). So do you want external references for the techniques? Or external references where you the reader could find the entire derivation? Or just an external reference for the results? I have lots of books, I am sure I could find any of those. @Dolphin51: Retired Pchem Prof (talk) 18:07, 24 January 2016 (UTC)

A whole section that contains no in-line citation is conspicuous. Even one in-line citation significantly improves the quality of the section. The math doesn't have to be verified, but I would like to see citation of at least one reliable, published source for each of the following statements:

"It is difficult to make accurate measurements of the Joule–Thomson coefficient, μ_JT, by the original method used by Joule and Thomson. It is also difficult to think physically about what the coefficient represents. However, it is possible to derive relationships between μ_JT and other, more convenient quantities."

"Since this is true at all temperatures for ideal gases (see expansion in gases), the Joule–Thomson coefficient of an ideal gas is zero at all temperatures."

Ideally, the in-line citation would address the sentence to which it is attached. If that isn't possible, the in-line citation would point to a source that talks about the topic.

Wikipedia's objectives regarding verifiability are well described at Wikipedia:Verifiability. Dolphin (t) 11:50, 25 January 2016 (UTC)

Done. Retired Pchem Prof (talk) 22:49, 28 January 2016 (UTC)

The draft section has now been placed in the article. Retired Pchem Prof (talk) 22:49, 28 January 2016 (UTC)