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

Printable Version  
Author: Subject: Eutectic salts for heating bath alternative
AnonGuy
Harmless
*




Posts: 5
Registered: 7-9-2023
Member Is Offline

Mood: No Mood

[*] posted on 2-2-2024 at 09:11
Eutectic salts for heating bath alternative


I'm not sure if this has been posted in the past, but I'm so happy with the results I thought I'd spread the good word.

So as we all know, oil baths are stinky and hazardous at high temps, sand has poor thermal conductivity, copper pellets/beads work well but its high density causes the flask to "float", making it very difficult to remove and replace. Heating mantles are great but not everyone has them.

I've recently started using molten nitrate salts and I'm quite happy with them. Very cheap, reusable, no smell, smoke, fumes, and good past 500C according to the paper. I've only done 280C so far myself, but haven't noticed any degradation or issues.

The only downside is it hardens back into a block when it cools, so storage is a bit of a pain. I just leave it in the pot and re-use. Also because of the calcium nitrate component the salt mix is a bit hygroscopic. It doesn't seem to be an issue however, as the moisture is driven off while its heating up.

https://www.osti.gov/servlets/purl/1142924

View user's profile View All Posts By User
Sir_Gawain
Hazard to Others
***




Posts: 271
Registered: 12-10-2022
Location: Due South of Due West
Member Is Offline

Mood: Yes.

[*] posted on 2-2-2024 at 10:50


And what happens when 300C nitrate comes into contact with something combustible?



“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
Rainwater
National Hazard
****




Posts: 800
Registered: 22-12-2021
Member Is Offline

Mood: indisposition to activity

[*] posted on 2-2-2024 at 12:06


Quote: Originally posted by Sir_Gawain  
And what happens when 300C nitrate comes into contact with something combustible?

A side reaction




"You can't do that" - challenge accepted
View user's profile View All Posts By User
AnonGuy
Harmless
*




Posts: 5
Registered: 7-9-2023
Member Is Offline

Mood: No Mood

[*] posted on 2-2-2024 at 13:07


At 280C, nothing happens. When I remove the flasks from the molten salt i place it on some newspaper to drip on.
View user's profile View All Posts By User
Rainwater
National Hazard
****




Posts: 800
Registered: 22-12-2021
Member Is Offline

Mood: indisposition to activity

[*] posted on 2-2-2024 at 14:12


Fuel + oxidizer, bad combination.
You'll get lucky 1000s of times, but that one time you dont, you will remimber.




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




Posts: 4278
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline

Mood: Semi-victorious.

[*] posted on 2-2-2024 at 14:23


I'm pretty sure the calcium nitrate is a tetrahydtrate to melt at that temp, and is far less likely to ignite something as, say, molten KNO3.



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
Twospoons
International Hazard
*****




Posts: 1282
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline

Mood: A trace of hope...

[*] posted on 2-2-2024 at 15:30


https://www.energy.gov/eere/solar/articles/halide-and-oxy-halide-eutectic-systems-high-performance-high-temperature-heat
Some ternary systems based on chlorides, if molten nitrates seem too risky.




Helicopter: "helico" -> spiral, "pter" -> with wings
View user's profile View All Posts By User
clearly_not_atara
International Hazard
*****




Posts: 2694
Registered: 3-11-2013
Member Is Offline

Mood: Big

[*] posted on 2-2-2024 at 16:21


Since the methanesulfonates can substitute for nitrate in dissolving silver, I thought I would look up their melting points and eutectic properties. The mp of NaOMs is about 354 C; CsOMs is about 263 C. But I couldn't find any information about eutectics of alkali metal salts or about KOMs. Most methanesulfonates decompose at about 400 C in air.

The chloride eutectics mostly have very high melting points, > 350 C. I assume that the interesting operating range is around 150-350 C, since beyond that there isn't much organic chemistry to do. Eutectics of sodium and potassium bisulfate are stable to around 300 C when they decompose into pyrosulfate.

The tetrachloroaluminates have excellent melting properties but I have always assumed they would be destroyed by moisture. Likewise iron and zinc. Even the chloride mixtures containing MgCl2 are suspect.

IIRC NiBr2 doesn't hydrolyze. Possibly a bromide eutectic containing nickel would be air-stable.

[Edited on 3-2-2024 by clearly_not_atara]




[Edited on 04-20-1969 by clearly_not_atara]
View user's profile View All Posts By User
Twospoons
International Hazard
*****




Posts: 1282
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline

Mood: A trace of hope...

[*] posted on 3-2-2024 at 14:58


T=132 C at NaCl-KCl-AlCl3 mole fraction of 36%-14%-50%.
T=91 C at NaCl-KCl-AlCl3 mole fraction of 26.25%-15%-58.75%.

From the linked presentation above.




Helicopter: "helico" -> spiral, "pter" -> with wings
View user's profile View All Posts By User
DraconicAcid
International Hazard
*****




Posts: 4278
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline

Mood: Semi-victorious.

[*] posted on 3-2-2024 at 17:15


Quote: Originally posted by Twospoons  
T=132 C at NaCl-KCl-AlCl3 mole fraction of 36%-14%-50%.
T=91 C at NaCl-KCl-AlCl3 mole fraction of 26.25%-15%-58.75%.

From the linked presentation above.

But that's going to be really water-sensitive, I think.




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
Deathunter88
National Hazard
****




Posts: 508
Registered: 20-2-2015
Location: Beijing, China
Member Is Offline

Mood: No Mood

[*] posted on 3-2-2024 at 19:49


Quote: Originally posted by Rainwater  
Fuel + oxidizer, bad combination.
You'll get lucky 1000s of times, but that one time you dont, you will remimber.


Molten nitrates are more inert than you would expect, and essentially resistant to detonation. Black powder has to be ball milled for hours and hours for intimate contact of the ingredients and even then in the open it is more of a gentle deflagration. Calcium nitrate isn't even used in black powder because of how poorly it performs as an oxidizer.

All that is to say, the OP has nothing to fear from his nitrate heating bath unless he does something incredibly idiotic, and I actually do think it is a good replacement for traditional oil baths.
View user's profile View All Posts By User
AnonGuy
Harmless
*




Posts: 5
Registered: 7-9-2023
Member Is Offline

Mood: No Mood

[*] posted on 3-2-2024 at 23:33


Quote: Originally posted by Deathunter88  
Quote: Originally posted by Rainwater  
Fuel + oxidizer, bad combination.
You'll get lucky 1000s of times, but that one time you dont, you will remimber.


Molten nitrates are more inert than you would expect, and essentially resistant to detonation. Black powder has to be ball milled for hours and hours for intimate contact of the ingredients and even then in the open it is more of a gentle deflagration. Calcium nitrate isn't even used in black powder because of how poorly it performs as an oxidizer.

All that is to say, the OP has nothing to fear from his nitrate heating bath unless he does something incredibly idiotic, and I actually do think it is a good replacement for traditional oil baths.


If anything i think the nitrate salts are much safer then oil baths. Granted i haven't gone to 500C, and have no intentions of doing so, but at 280C pretty much anything aqueous and probably a whole lot of other stuff will cause an oil bath to turn into a volcano(if you could even reach those temps; synthetic oil perhaps?).

Not so much with this stuff. I carefully added some water expecting a violent reaction. Got just a bit of steam. :D

Now I'm sure there are substances that'd cause a violent reaction if mixed with the nitrate salt, but that's a poor argument against the method, since just about everything and anything will cause that same issue with oil baths, at much lower temperatures in fact. Also most oils are quite flammable, so you have the terrible side effect of a fireball being emitted from the spill as well!

I'm not going to tell you i didn't have trepidation when i first melted up some nitrate and plunged in my 5L flask though. :o

Truth be told, I just ordered a very large heating mantle so I probably wont be using this method much longer, but I found it to be superior to anything else I've tried to date.

The only other thing I considered trying is different low mp metal alloys. However from what i can tell they usually have toxic metals as a component(s), are probably more expensive and may also react violently to contaminants.

[Edited on 5-2-2024 by AnonGuy]
View user's profile View All Posts By User

  Go To Top