Talk:Frigorific mixture

Image

The table image should be made into a proper table, with wikilinks. --Classical geographer (talk) 09:23, 26 June 2008 (UTC)

---

A more modern table with temperatures in C is desirable until present it should be pointed out that the table is in F. A frigoforic mixtures produces low, but not necessarily constant temperatures. However, for ice-based mixtures, if the salt or other compound is present in large enough amounts to form a saturated solution with the melt water this would be the case. Considering the large amount of heat liberated on dilution of sulphuric acid it is surprising, and possibly doubtful, that the dilute acid (how dilute?) would form an efficient frigoforic mixture with ice. The temperature claimed for two rather similar mixtures of this kind are remarkably different! —Preceding unsigned comment added by 90.239.71.36 (talk) 23:56, 24 July 2010 (UTC)

---

Fahrenheit entry states zero for ammonium chloride, while the Figoritic Mixture speaks about sodium chloride mixture being the zero point of Fahrenheit scale. Which is correct?

The last entry, explaining shrink fitting, is unnecessary in current context. I think that the statement that shrink fitting is appropriate, but the description thereof is misplaced (though the description is well stated).

Please forgive me if I failed to meet the talk page guidelines.

174.51.253.230 (talk) 05:07, 10 December 2009 (UTC)

'Chemical'?

The article states 'mixture of two or more chemicals', and then goes on to mention water and ice. Aren't water and ice chemically identical? Isn't a chemical independent of its temperature (at least at sub-plasma temperatures)?

Suggest substituting 'substance' for chemical. Liquid water and ice are arguably different substances.

I'm not making the change to allow someone more intimate with The Mysteries Of Chemistry to tell me I'm a fool. 87.194.43.133 (talk) 11:33, 7 August 2010 (UTC)

Although this section is nearly 11 years old now and what I believe you were referring to has now been changed, I would still like to offer up an explanation for anyone else that may be confused. Before I begin, I would like to stress that I am by no means an expert and I encourage the reader to draw their own conclusions from more reputable sources. I merely write this in the hope that it might clarify the meaning of certain parts of this article.

Your argument about water and ice being the same chemical seems completely valid (at least to me), however, this example in which water and ice are mentioned does not contradict the statement 'mixture of two or more chemicals'. This is because the two or more chemicals (two in this case) are H₂O and NaCl. The reasoning behind mentioning the presence of water and ice in this example is because having two phases of H₂O as well as the one phase of the NaCl (hydrohalite) in this mixture is what makes it frigorific!

Having two chemicals (H₂O and NaCl) and three phases (liquid water, water ice, and hydrohalite) present creates a frigorific mixture due to the phase rule. The phase rule states: if F = number of degrees of freedom, C = number of chemical components, and P = number of phases, then

$F=C-P+2$

In our example, we have 2 substances and 3 phases, so if we substitute our values into the equation we end up with an F value of 1.

$F=(2)-(3)+2$

The phase rule, therefore, states that our mixture of liquid water, water ice, and salt only has one degree of freedom. This means that there is only one independent physical parameter and all others will be dependant. As a result, this frigorific mixture can exist only at one temperature for any given pressure and vice versa. This is contrasted by a substance that possesses two degrees of freedom, such as pure liquid water. Liquid water's possession of two degrees of freedom is shown by the fact that it is able to exist at many different temperatures while at atmospheric pressure, and by the fact that it is able to exist at many different pressures while at the same temperature. Since our independent parameter is forced onto us (atmospheric pressure), other parameters such as temperature become dependent. This is the cause of the rapid temperature change that the mixture would experience while reaching equilibrium (while in the atmosphere). -- Epsiboy (talk) 13:35, 3 April 2021 (UTC)

Phlogiston revisited

This article is NONSENSE! The heat of dissolution is either positive or negative (or zero). It is dependent on the temperature, slightly!!, it will NOT control the temperature of the mixture!! Note that the citation is from 1862 and an Army manual. We get our scientific facts from the U.S. Army (or was it Confederate?)?!?!? Cooling causes additional dissolution?? Lechatliere's Principle is violated! (since the reaction is claimed to be endothermic). Teh reaction will NOT suddenly turn exothermic upon cooling to some set temperature. If it is endothermic, it will continue to cool the mixture until it becomes dilute enough to have no further effect or until some other phase change occurs (say, freezing of the mixture). The equilibrium temperature will depend on the initial temperatures of the system's components, their heat capacities and the heat of reaction of the various mixtures and phases produced. It is NOT controlled by the mixture independent of the initial temperatures!!! Could we get a PhD Physical Chemist (or Engineer) to review this please? I'm not sure if it can be salvaged or should become a historical oddity of an example of a theory which is just plain wrong. Either way more citations are needed. There seems to be a lot of confusion about whether this is a open, closed or isolated system. Counter-example one. NaCl and H2O are mixed at -200°C (both are fine powders, say). What will the temperature be after mixing? Not 0°C !!! Counter-example two. NaCl and H2O are mixed at 1500°C. What will be the temperature after mixing. Absolute rubbish. I can understand why these mixtures would be used to cool or heat, but not the silly claim that they maintain a system's temperature independent of the initial conditions.69.40.241.198 (talk) 00:12, 14 February 2011 (UTC)

Obvious flaws

This article has barely changed since its original upload in 2007, despite 41 edits by 33 different users (since the original author's work) and some obvious flaws:

1. No indication of whether "parts" are by mass, volume or what
2. Gives the temperatures only in a scale that is in use only in about 2% of the world
3. Uses a notation to represent said scale that in most of the world denotes angle, not temperature
4. Somebody has decided for no apparent reason that "Thermometer" is a proper noun
5. No clue of what the "from" temperature means – why would it necessarily have been at a particular temperature to start with?
6. No scientific explanation whatsoever of how frigorific mixtures work – this is something that people are likely to come here looking for.

Why, in over 6 years, has nobody fixed these already?

I can easily fix 2, 3 and 4. I'll remove the "from" temperatures pending an explanation of them. But 1 and 6 would need somebody with the knowledge to supply the information. — Smjg (talk) 00:00, 14 February 2014 (UTC)

Fixed some conceptual and nomenclature problems, invoked Phase Rule

Hopefully the explanation makes sense now. I have invoked the Gibbs Phase Rule, which explains why frigorific mixtures exist, and clarified why the temperature spontaneously changes until equilibrium is achieved. — Preceding unsigned comment added by Asimow (talk • contribs) 01:41, 22 June 2017 (UTC)

Mixture ratio

Please make sure that w/w is the mass fraction or the mass ratio of the mixture. Big difference. 31.46.247.191 (talk) 10:25, 16 October 2023 (UTC)