Talk:Eutectic system/Archive 1

Archive 1

Gold and Silver contradiction

The article gives the gold-silver system as an example with no eutectic point. However, soldering with gold and silver is named as an example application later on. Could an expert clarify this? Ziglum (talk) 10:43, 13 February 2009 (UTC)

Sodium Chloride and Water example

The example about melting iced roads by salting them is rather misleading to me, since as far as I know it has nothing to do with the fact that the saltwater solution is or isn't a eutectic. Is it worth mentioning it in this context? -Kade304 (talk) 21:27, 24 September 2008 (UTC)

Eutectic Point

This article needs a lot of work. There are few references to metallurgical applications and there is no discussion of Gibbs phase rule and invariance. The article appears to be solely confined to binary eutectic examples. If I get time over the next few weeks I may attempt a clean up. —Preceding unsigned comment added by Byrdbraine (talk • contribs) 20:35, 29 August 2008 (UTC)

Phase notation

I just looked at the diagram for a while and couldn't figure out what the regions denoted "alpha" and "beta" were. I then realized that the description in the text is wrong (or at least unclear) in that the two components are not the pure metals, but saturated solutions of one in the other. Please correct me if I'm wrong, otherwise I will correct the text in the next few days. --Alban 14:57, 24 Jun 2005 (UTC)

You're right in the case of the eutectic components; however, any composition & temperature within the region labelled alpha (including the pure component along the leftmost edge) is also alpha. It's important to note that (at least in the example) the phases produced have the same structure as the two pure components. Please do clarify this in the article if you can.--Joel 21:36, 24 Jun 2005 (UTC)

This book[1] calls it a "solid solution". Yes please do clarify. Samw 00:04, 25 Jun 2005 (UTC)

alpha and beta are the hypo and hyper eutectic solid solution (respectively). These solid solutions are present in all simply binary eutectics. Neither one these solid solutions are only saturated when the composition of the alloy approaches infintesimally close to the line between the solid solution and the peritectic phase (solid and liquid). Iepeulas 23:19, 17 June 2006 (UTC)

Just to clarify a little more, the alpha phase has very similar crystal structure to the 'pure' left side metal, while the beta phase has a very similar crystal strcture to the right side metal. In some aloys, it is posible to see bands of alpah and beta intermingled in the alpha+beta phase which is not seen in either the alpha or beta phases.

Lowest-melting

Hmm...I always thought that eutectic means, more or less, a mixture of two or more substances whose melting point is lower than that of any of the constituent substances. In what way does the definition given in the article correspond to this definition? Could someone knowledgeable in physics clarify this a little? Kosebamse 20:53 Mar 24, 2003 (UTC)

Eutectic is more specific than that: it's the mixture whose melting point is the lowest. Since it's such a special point, there all kinds of other mathematical/physical ways to define it, which are all equivalent but which are useful in different contexts. The interesting thing is that any mixture that's fairly close to eutectic composition & only slightly above eutectic temp. will be "mushy" (yes, that's a technical term), with the off-eutectic component frozen out & eutectic liquid remaining. --HTHPolyparadigm 17:42, 8 Apr 2005 (UTC)

Wrong, the term eutectic is a very specific mixture, and it only occurs when phase boundaries arrange in a certain way. In the "Phase Diagram" section there is a perfect example of a eutectic "phase". A eutectic "phase" is really just a mixture of two other elements that arrange themselves in a order that depends on the cooling rate, diffusion rate, and many other things. A regular eutectic mixture usually arranges itself into a series of plates which is known as a lamellar structure but sometimes it arranges itself into a rod like structure. Irregular eutectic structures which are more common look more like rounded scribbles or "Chinese Script" but there are many different Irregular structures that eutectic mixtures form. A eutectic "phase" only occurs when two other phases meet at a point, that points downward, for example you have an alpha+l on the left, the liquid phase meeting down the middle, and a beta+l phase would meet on the right with a alpha+beta phase below the eutectic temperature, the alpha+beta phase would be eutectic. Any other arrangement than the one that I specified would not be eutectic, it may be peritectic, eutectoid, or peritectoid. I will make a diagram with all of them listed and post it (if I can, I am kind of new here.) Willydw131 14:15, 8 Apr 2005 (UTC)

Here is the Diagram listing the most important three phase reactions in a binary system, as well as a eutectic type phase diagram and a peritectic type phase diagram. Willydw131 16:09, 8 Apr 2005 (UTC)

File:Three-Phase-Reactions.png

Three-Phase Reactions

File:Phase-Diagrams.png

Eutectic/Peritectic Phase Diagrams

German text

The following german text was added to the article anonymously:

Die eutektische Mischung ist ein Gemisch zweier oder mehrerer kristalliner Feststoffe in der durch einen minimalen Schmelzpunkt ausgezeichneten Zusammensetzung. Im Fall des binären Systems Lidocain/Prilocain hat das Eutektikum eine Zusammensetzung von 1:1 und sein Schmelzpunkt beträgt lediglich 18º C, während die Einzelsubstanzen bei 67º C bzw. 37º C schmelzen. Viele Metalle haben die Eigenschaft, einander im geschmolzenen Zustand zu lösen. Die Erstarrungsprodukte solcher Lösungen sind als Legierungen weithin bekannt. Löst man ein Metall A in einem Metall B, so wird zuerst der Schmelzpunkt von B erniedrigt, bis zu einem Punkt (eutektischer Punkt) an dem der Schmelzpunkt wieder Ansteigt, um sich mit zunehmenden Gehalt an A in der Mischung dem Schmelzpunkt von A annähert. Die Legierung, die durch Erstarren der Mischung am eutektischen Punkt entsteht, nennt man auch eutektische Mischung.

Someone want to translate and fit it into the article? It sounds like taken from a chemistry textbook... andy 09:27, 7 Aug 2003 (UTC)

It seems to have been taken from taken from http://www.multimedica.de/public/fachportal/derma/020/070/804.html, which looks like it's copyrighted. Ievertheless, I'll rewrite and translate it, but my knowledge of physics is very limited so the text will need to be checked.

Water & alcohol

Removed the paragraph: "You can see a macroscopic eutectic crystal by freezing a water/alcohol mix in a household freezer. I have made crystals 3 or 3 cm in size, made from leaves of water ice separated by liquid alcohol. I was attempting to fortify some home-brewed mead at the time."

Removed because it is original research and wiki is not a place for that. Also I don't think this has anything to do with eutectics, he's simply seeing fractional crystalization of the water out of solution, though I'm not a chemist and if I'm wrong I welcome correction by someone who is one.--Deglr6328 16:22, 13 Aug 2004 (UTC)

Absolutely correct. Eutectic freezing would result in both water and alcohol crystals simultaneously, and they'd be too finely interleaved to see: the only reason the water crystals could get so big in his experiment was the fast diffusion through liquid alcohol. This is because his solution was off-eutectic (too much water, the problem he was trying to solve!). If he froze it completely (we're probably talking cryogenic, here) and looked in a microscope, the solid holding his ice together would be a eutectic of water & alcohol, or more likely a multicomponent eutectic if he wasn't using vodka. Everclear is at the eutectic composition, if I'm not mistaken.--Polyparadigm 17:42, 8 Apr 2005 (UTC)

Merging Peritectic

As a mechanical engineering student, I disagree with the notion that merging peritectic into this article is appropriate. The articles should not be merged. — Scm83x ^talk 06:49, 9 March 2006 (UTC)

I strongly concur. Don't merge. It could be listed in the "see also", perhaps... --Joel 21:08, 3 April 2006 (UTC)

Requested move

Rationale: Current title is badly formatted, plus article titles should be nouns. … Please discuss/vote here — —Keenan Pepper 23:49, 4 April 2006 (UTC)

Just so we're clear, is this the plan?

page	current contents	change
Eutectic(Chemistry)	mixed melting point meaning	move to Eutectic point
Eutectic(Mascot)	college mascot (but page not yet created)	no change, or move to Eutectic (Mascot)
Eutectic	disambig for Eutectic(*)	redirect to Eutectic point

• support: agree with rationale here, and on Talk:Eutectic that the mascot is a less-common and less-important use for the primary term. DMacks 00:42, 5 April 2006 (UTC)
• neutral: I prefer "eutectic" being the main article. While it's technically an adjective, it is the commonly used word. Perhaps eutectic point could redirect to eutectic? Regardless, the current arrangement of eutectic being a disambig is just plain wrong. Samw 01:30, 5 April 2006 (UTC)
• neutral: A Peritectic reaction is completely different than a eutectic one. A eutectic "phase" is completely different than the phase that developes below a peritectic line. Peritectic, Peritectoid, and Eutectoid reactions should be added to eutectic or better yet place all of them under the category "Phase Diagrams" because that is where they belong. The term "Eutectic" when said alone commonly means Eutectic Microstructure which may or may not be what you want to name the category. Billy D 02:59, 11 April 2006 (UTC)

Moved to Eutectic point. —Nightstallion (?) ^{Seen this already?} 07:36, 10 April 2006 (UTC)

• disagree: OED lists 'eutectic' as both an adjective and a noun. 'Eutectic' is more common, and is a suitable place for the main article. —DIV 128.250.204.118 00:35, 14 February 2007 (UTC)

As a material scientist and pedant, I completely disagree with this article being called "Eutectic Point". We could easily have another article about a eutectic point, although it is probably more useful on an article about phase diagrams in general. The invariant eutectic reaction on a binary alloy, the eutectic point and the eutectic phase or structure consisting of combinations of two 'true' phases are completely different thermodynamic and metallurgical terms and should be separated. This article as it currently stands is not clear. Perhaps when I finish my current set of examinations I might attempt to add some clarifications. Mike 23:27, 31 May 2007 (UTC)

Cryohydrate

Can anyone provide a good definition of a cryohydrate? It may be useful to menion in the article. 128.250.204.118 00:35, 14 February 2007 (UTC)

Archive 1