Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Creating eutectics
helzblack
Harmless
*




Posts: 31
Registered: 6-8-2019
Member Is Offline


[*] posted on 11-10-2024 at 11:02
Creating eutectics


So I have never made an eutectic salt. I want to make the salt-potassium chloride eutectic.

Do I have to mix them forcefully with a mortar? Dissolve them and then evaporate the water?

How is the eutectic made, it is supposed to melt at around 600C
View user's profile View All Posts By User
Rainwater
National Hazard
****




Posts: 912
Registered: 22-12-2021
Member Is Offline

Mood: indisposition to activity

[*] posted on 11-10-2024 at 13:41


What other compound are you mixing with the KCl?
To the best of my knowledge, KCl will decrease the melting point of water and a few other organic solvents
It will decrease the melting point of calcium chloride when mixed to a ratio of 70% KCl
(going off memory here, lots of crc errors)
https://www.sciencedirect.com/science/article/abs/pii/S09270...

[Edited on 12-10-2024 by Rainwater]




"You can't do that" - challenge accepted
View user's profile View All Posts By User
Fulmen
International Hazard
*****




Posts: 1712
Registered: 24-9-2005
Member Is Offline

Mood: Bored

[*] posted on 11-10-2024 at 23:21


You need to melt them together. Once one of the components melts the others will start dissolving into it. Finely ground and mixed materials will probably melt faster, but not at a lower temperature.



We're not banging rocks together here. We know how to put a man back together.
View user's profile View All Posts By User
helzblack
Harmless
*




Posts: 31
Registered: 6-8-2019
Member Is Offline


[*] posted on 12-10-2024 at 05:45


@Rainwater Salt and Potassium Chloride
NaCL and KCL
View user's profile View All Posts By User
chornedsnorkack
National Hazard
****




Posts: 563
Registered: 16-2-2012
Member Is Offline

Mood: No Mood

[*] posted on 12-10-2024 at 07:05


Quote: Originally posted by Fulmen  
You need to melt them together. Once one of the components melts the others will start dissolving into it. Finely ground and mixed materials will probably melt faster, but not at a lower temperature.

Is it so? Compare water and salts. The eutectic is -21 for NaCl, lower for some other salts. If solid NaCl and solid water are brought to contact at say -10 degrees, will solid-solid contact initiate melt formation, or will there be no reaction till they are warmed to 0 degrees?
View user's profile View All Posts By User
Fulmen
International Hazard
*****




Posts: 1712
Registered: 24-9-2005
Member Is Offline

Mood: Bored

[*] posted on 12-10-2024 at 08:25


Fair point. As you come close to the melting points there is bound to be some interaction. So in theory you should be able to form the eutectic slightly below the melting point. But it's going to be a slow process compared to melting the ingredients together.

[Edited on 12-10-24 by Fulmen]




We're not banging rocks together here. We know how to put a man back together.
View user's profile View All Posts By User
Deathunter88
National Hazard
****




Posts: 518
Registered: 20-2-2015
Location: Beijing, China
Member Is Offline

Mood: No Mood

[*] posted on 12-10-2024 at 08:32


Quote: Originally posted by chornedsnorkack  
Quote: Originally posted by Fulmen  
You need to melt them together. Once one of the components melts the others will start dissolving into it. Finely ground and mixed materials will probably melt faster, but not at a lower temperature.

Is it so? Compare water and salts. The eutectic is -21 for NaCl, lower for some other salts. If solid NaCl and solid water are brought to contact at say -10 degrees, will solid-solid contact initiate melt formation, or will there be no reaction till they are warmed to 0 degrees?


Yes the solid water would melt - this is precisely how road salt works to melt snow and ice.
View user's profile View All Posts By User
Bedlasky
International Hazard
*****




Posts: 1233
Registered: 15-4-2019
Location: Period 5, group 6
Member Is Offline

Mood: Volatile

[*] posted on 12-10-2024 at 17:22


Awesome eutectic is LiCl-KCl. 41,8 mol % KCl, 58,2 mol % LiCl (anhydrous). Mixture melt at 352 °C, which is very low for ionic chloride mixture.
View user's profile View All Posts By User
DraconicAcid
International Hazard
*****




Posts: 4320
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline

Mood: Semi-victorious.

[*] posted on 12-10-2024 at 17:49


Quote: Originally posted by Bedlasky  
Awesome eutectic is LiCl-KCl. 41,8 mol % KCl, 58,2 mol % LiCl (anhydrous). Mixture melt at 352 °C, which is very low for ionic chloride mixture.

Molten lithium salts will weaken glass. You get slow ion exchange which makes the glass very brittle.




Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
View user's profile View All Posts By User
knowledgevschaos
Harmless
*




Posts: 41
Registered: 9-8-2023
Location: Sci-Hub and the hardware store
Member Is Offline

Mood: Hungry for information

[*] posted on 13-10-2024 at 02:06


Phase diagrams are super useful for this kind of thing.
This website has a great article on how they work. Although it's specialized for the alloys of metals, everything should still apply for eutectic salts.




Know thy incompatibilities
View user's profile View All Posts By User
Fulmen
International Hazard
*****




Posts: 1712
Registered: 24-9-2005
Member Is Offline

Mood: Bored

[*] posted on 13-10-2024 at 12:10


The KCl/NaCl eutectic is pretty underwhelming (650/800C). Adding MgCl2 can drop it under 500C, I'm going to try that as a flux for molten aluminum in a future project.

If you're just after cool eutectics I would study the K/Na/CaNO3-system. The constituent salts melt from 300-550C, the eutectics go down to 160C.





We're not banging rocks together here. We know how to put a man back together.
View user's profile View All Posts By User
Rainwater
National Hazard
****




Posts: 912
Registered: 22-12-2021
Member Is Offline

Mood: indisposition to activity

[*] posted on 13-10-2024 at 12:52


Quote: Originally posted by Fulmen  
K/Na/CaNO3-system.

I accidentally mixed sodium and potassium metal. It was not nice.
It is very unpleasant to depose.
1 drop of water into the alloy was too explosive, so i thought to drip the mix into an extreme excess of water. It worked great until it didn't
Eat through a ptfe stopcock in a seperation funnel and leaked out very, very fast, instantly ignited my table, bucket, grass. Big booms and puffs, flashes, and pops.
1 of 5 stars will not repeat.

Leftovers turned yellow, poked with a stick from far away. Instant pops.
Wear ear protection
3 of 5 stars would recommend to a friend.




"You can't do that" - challenge accepted
View user's profile View All Posts By User
Sir_Gawain
Hazard to Others
***




Posts: 397
Registered: 12-10-2022
Location: Due South of Due West
Member Is Offline

Mood: Way less sad

[*] posted on 13-10-2024 at 14:14


I think he’s referring to a mixture of all three nitrates. Not elemental Na/K.



“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
View user's profile Visit user's homepage View All Posts By User
Morgan
International Hazard
*****




Posts: 1694
Registered: 28-12-2010
Member Is Offline

Mood: No Mood

[*] posted on 13-10-2024 at 17:16


When doing some experiments/toying with solid rock salt, I thought it would be nice to make my own solid rock salt, but the melting point is annoyingly high. I was able to melt or glaze the surface of some table salt with a simple torch but beyond that of course it's more effort to melt it so the idea of a eutectic appealed to me. It would be nice if a eutectic could retain or improve the high thermal expansion property of rock salt.
When the physicist John Tyndall was studying the Trevelyan Rocker, on this topic, of all the minerals he experimented with, he found rock salt to be the best. "I scarcely know a substance, metallic or non-metallic, with which vibrations can be obtained with greater ease and certainty than with this mineral."

A few random experiments tried with salt.
https://www.youtube.com/watch?v=jlD1EGEieC0
https://www.youtube.com/watch?v=5bu01y_6LJU
https://www.youtube.com/watch?v=Yet6p4ja7qQ
https://www.engineeringtoolbox.com/linear-expansion-coeffici...

One curious tidbit if anyone knows, is it possible that this very tiny spark from this tiny hot brass fitting was caused by an electrostatic discharge when set upon the salt? It occurs at the the 10 second mark and it's very faint. I haven't been able to reproduce it, hoping to amplify it if possible.
https://www.youtube.com/watch?v=i-7kbkVx8bI
View user's profile View All Posts By User
Fulmen
International Hazard
*****




Posts: 1712
Registered: 24-9-2005
Member Is Offline

Mood: Bored

[*] posted on 14-10-2024 at 02:19


Quote: Originally posted by Sir_Gawain  
I think he’s referring to a mixture of all three nitrates.

You are correct, my apologies for the confusion. It is of course KNO3/NaNO3/Ca(NO3)2. NaK is pretty cool, but not really suited for amateurs. And combining it with nitrates sounds like a bad day in the lab for everyone.

[Edited on 14-10-24 by Fulmen]




We're not banging rocks together here. We know how to put a man back together.
View user's profile View All Posts By User
helzblack
Harmless
*




Posts: 31
Registered: 6-8-2019
Member Is Offline


[*] posted on 15-10-2024 at 04:12


Quote: Originally posted by Fulmen  
The KCl/NaCl eutectic is pretty underwhelming (650/800C). Adding MgCl2 can drop it under 500C, I'm going to try that as a flux for molten aluminum in a future project.

If you're just after cool eutectics I would study the K/Na/CaNO3-system. The constituent salts melt from 300-550C, the eutectics go down to 160C.


And how do you plan to mix them to make the eutectic? Mortar and pestle? I have heard that it must be forcefully and intimately mixed, hence why I am asking if this is correct?

[Edited on 15-10-2024 by helzblack]
View user's profile View All Posts By User
chornedsnorkack
National Hazard
****




Posts: 563
Registered: 16-2-2012
Member Is Offline

Mood: No Mood

[*] posted on 15-10-2024 at 04:24


I am unsure that a double eutectic needs forceful mixing. A triple eutectic might.
View user's profile View All Posts By User

  Go To Top