Talk:Critical point (thermodynamics)

message: I don't think that critical point drying should be merged into this article. It is a big enough topic to support an article of its own. Of course, the article in its present state is pretty bad. Hopefully it will be fixed up soon. -- Kjkolb 09:51, 10 February 2006 (UTC)
thread_title: Merge

message: This subject seems to focus on chemical critical points wrt temperature and phase changes of homogeneous stuff.  But shouldn't it also include the criticality associated with limit cycles of systems far from equilibrium (i.e., dissipative systems)?  Just a thought.  If I knew more I would put it in.  Rhetth (talk) 14:59, 13 August 2009 (UTC)
replies: text: I think this is some other critical point not thermodynamic critical point.  Generally one is talking about a closed system wrt thermodynamic properties.  A dissipative system is a thermodynamically open system which is operating out of, and often far from, thermodynamic equilibrium in an environment with which it exchanges energy and matter.  Also the discussion on mixtures is woefully inadequate.  Sometimes the PVT - X relationship can be taken to be linear in which case the critical properties can be estimated using KAY'S RULE, e.g. -- MCP (mixture critical pressure) = the number or molar average across the pure component critical pressures.  For example, in a 60-40 molar mixture of n-pentane and pentene-1, Pc (mixture) = 0.6*Pc (n-pentane) + 0.4*Pc (pentene-1). However, sometimes it is highly non linear requiring more homework to develop the PVT data of different X's.  This is not a good example because n-pentane and pentene-1 state properties are so close together.Danleywolfe (talk) 22:50, 18 July 2011 (UTC)
thread_title:  New section on chaotic instabilities 

message: In thermodynamics, pure substances are usually considered simpler or more fundamental than 2-component systems. I suggest therefore describing the vapor-liquid critical point of pure materials before the liquid-liquid critical point of binary systems. Does anyone object to rearranging the article to place the present section 2 before section 1?  Dirac66 (talk) 19:06, 8 September 2009 (UTC)
thread_title:  Pure substances first? 

message: Would it be graphite? What would be the temperature, approx?
[Question by 142.103.44.67 dated 5 April 2011]
:First I have this moved this new section to the end of the talk page.
:Graphite is a solid form of carbon, whose liquid-vapor critical point is estimated at 6810 K (HR Leider et al, Carbon, 11, 555-563 (1973). This is lower than the values in the article for Fe, Al and Au. So for now the highest value in Wikipedia is Fe at 8500 K. Does anyone know a higher one?
:I think also that all these values are only theoretical estimates, since at such high temperatures there is no container that will hold a liquid. Dirac66 (talk) 14:04, 6 April 2011 (UTC)
thread_title: What material has the highest critical temperature

message: "The existence of a critical point was first discovered by Thomas Andrews in 1869 for carbon dioxide." This sentence may need modification. The discovery of the critical point for carbon dioxide may be first discovered in 1869 but the existence of the critical point was discovered by Charles Cagniard de la Tour in 1822. (http://en.wikipedia.org/wiki/Charles_Cagniard_de_la_Tour) --Mirrordor 17:58, 28 September 2011 (UTC)
replies: text: Apparently Cagniard de la Tour made the first known observation, and Andrews went much further. So we have to sort out what each actually contributed. A possible starting point is this paper Critical phenomena: 150 years since Cagniard de la Tour by Berche et al. (2009) Dirac66 (talk) 18:20, 28 September 2011 (UTC)
thread_title:  History 

message: If there is a critical point, above which gas & liquid are effectively indistinguishable; then perhaps there is another critical point, above which liquid & solid are indistinguishable?  Cp. material in earth's mantle, which is said to be solid, yet which flows under load.  Perhaps, too, plasmas plot far to the right, above-and-beyond all critical points, so that plasmas compress continuously, from gas-like (low P) through liquid-like to sold-like (high-P)?  Ultimately, at super-high pressures, perhaps materials compress into "neutronium", as speculated to exist inside of neutron-stars?  Cp. the following figure:
::http://s17.postimage.org/ecdbmzq3j/All_Phases_diagram.png
:66.235.38.214 (talk) 04:13, 15 October 2012 (UTC)
replies: text: This suggestion is speculative. Although many have wondered if there might be a liquid-solid critical point, I am unaware of any actual evidence for one. Dirac66 (talk) 13:42, 15 October 2012 (UTC)
thread_title: Liquid-solid critical point?

message: This section In renormalization group theory should perhaps move to that article - does not seem relevant here. This is not a disambiguation page. - Rod57 (talk) 12:53, 29 April 2017 (UTC)
replies: text: The section is in fact about one theory which describes critical points and critical phenomena at a more advanced level, so I have moved it to the more advanced article Critical phenomena, which seems a more appropriate place for it. Dirac66 (talk) 01:56, 2 May 2017 (UTC)
thread_title:  ''In renormalization group theory'' seems out of place 

message: A brief mention and links to some other critical phenomena would be very helpful, if they exist: I suspect that the Curie point could go here, maybe Néel point... perhaps there are others. Latrissium (talk) 20:48, 17 November 2017 (UTC)
thread_title:  Some other physical examples would be useful 

message: The expression given for reduced volume looks incorrect. Typically one states the critical molar specific volume 
 V_{m,c}=3b=\frac{3}{8}\frac{RT_c}{p_c} 
as in the article on the Van der Waals Equation. The reduced volume  V_r  is then given in terms of the molar specific volume  V_m  and the critical molar specific volume  V_{m,c}  as
 V_r = \frac{V_m}{V_{m,c}} = \frac{V_m}{\frac{3}{8}\frac{RT_c}{p_c}}.  Eshort0401 (talk) 08:57, 6 December 2022 (UTC)
replies: text: This formula would need a source to be taken seriously, according to the rules of Wikipedia. Dirac66 (talk) 02:36, 18 March 2023 (UTC)
thread_title:  Reduced Volume Error 

message: The redirect Critical point (physics has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at  until a consensus is reached.  Utopes (talk / cont) 01:12, 20 January 2024 (UTC)
thread_title:  "[[:Critical point (physics]]" listed at [[Wikipedia:Redirects for discussion|Redirects for discussion]]