I need appr 4kg of a low melting salt mixture for a tempering bath. I'd like to get below 200°C, which in it self isn't that hard, the challenge is
availability of chemicals. Basically I have sodium and calcium nitrate, and assuming the reduction with lead works sodium nitrite as well.
I've been searching like mad, but most mixtures uses potassium nitrate and even more exotic salts like lithium. Does anybody have a good source for
useful compositions?
One source claims 145°C for 50/50 NaNO3/NO2 while other sources say 220+, so it's hard to know where to start. DraconicAcid - 12-7-2015 at 08:02
Calcium nitrate tetrahydrate melts at around 40 oC, and loses water at 132 oC.UC235 - 12-7-2015 at 08:29
A LiNO3/NaNO3 eutectic can get you to 195C. KNO3/NaNO3 eutectic will get you to 223C.
LiNO3/KNO3 is very low-melting at 125C.
Of course, LiNO3 is fairly expensive and that website doesn't have nitrites included.Magpie - 12-7-2015 at 09:48
I have used the tin/bismuth eutectic (mp =139°C) but I needed less than a kg.Fulmen - 12-7-2015 at 14:39
To elaborate a bit, I need a annealing/tempering-bath that can operate in the <200-400+°C range for hardening and tempering steel. And as I need
at least 2l (4-5kg in the case of nitrate salts) I need something cheap and available. The Bi/Pb/Sn-alloys are interesting, but the density would make
steel float. And then there's the fact that I would need 20kg...
UC235: Wonderful source, but sadly it does not contain any useful candidates. Unfortunately I am completely out of KNO3, as most mixtures seems to
rely on that. And KNO3 has become increasingly hard to get in recent years. I would prefer to avoid the nitrites as well (suspected carcinogenic and
teratogenic), but compared to the dangers of hot molten salts I'm not sure if that is any real issue. And as I have both sodium nitrate and lead it is
at least something I could make.
Best candidate so far is 46:24:30 K-Na-Ca nitrate with a listed mP of 160 C. UncleJoe1985 - 13-7-2015 at 23:51
I've been searching for low melting NaCl mixtures so I can make sodium metal and came across this excellent compilation of eutectic mixtures:
There's a lot more nitrate mixtures that you could try.
AlCl3 mixtures also have very low melting points but getting the anhydrous salt is pretty hard. Putting Al in hydrochloric acid will produce the
hydrate, which according to Wikipedia, cannot be heated to get the anhydride.
Fulmen - 14-7-2015 at 02:02
Thank you sir, this was exactly what I was looking for.
I'm focusing on nitrates only as I know these are used for heat treatment. And I have been advised against chlorides by a metallurgist, and while he
didn't give any detailed reasons I have no reason to doubt his expertise.
What I was hoping for was a Ca/Na NO3 mix below 200C, but no such luck. At 31 mol% it has a mp of 214C, which isn't that bad really.
Edit: Dang, I thought I found a good one at 154C, but that was with Ca(NO2)2. So 214°C it is, I can live with that as long as I don't have to make
any chemicals.
[Edited on 14-7-15 by Fulmen]Fulmen - 14-7-2015 at 11:20
Huh! I threw together a quick test, but got nowhere. The mix was listed as Ca(NO3)2-NaNO3, 31 mol%, which I assumed was 31 m% NaNO3. Could it be 31%
Ca?Zyklon-A - 14-7-2015 at 18:41
Generally the material with the highest concentration is listed first. So most likely sodium is 31%.franklyn - 21-7-2015 at 17:59
Thank you, I'll have a look and see if there is anything useful there as well.AlbinoMoose308 - 22-7-2015 at 12:34
I took a look at that PDF and it seems the first concentration is for the first of the two components. For example the concentration of #86 is listed
as 8.1-87.6-4.3. You need 31% Ca(NO3)2.aga - 22-7-2015 at 13:36
Much in the same way the other +1, +3, +5 and +7 Oxidation Number chlorine compounds exist: see hypochlorites, chlorates and perchlorates.
[Edited on 23-7-2015 by blogfast25]Fulmen - 23-7-2015 at 09:49
Albino Moose: Logic dictates it has to be either one or the other, right? I'll try the reverse proportions when I feel like working again. Bert - 23-7-2015 at 15:37
Fulmen, what part of the world are you in?
Are you heat treating steel tooling, knives, or ??? Any particular alloys and profiles you could disclose?
There's over 500lb. of Potassium nitrate, plus good quantities of all the other common nitrates on site here, and one of my crew is an amateur
blacksmith.Rosco Bodine - 23-7-2015 at 18:58
Here's a useful table for mixed nitrates eutectics made anhydrous by heating
That Ca/NH4/Na nitrate 18/69/13 eutectic mixture melting @ 107 C. sounds quite interesting for other things than an annealing bath... Given that
pyrotechnic reactions tend to start in earnest at the temperature where the oxidizer becomes molten .
Unfortunately, it would likely be rather hygroscopic.Fulmen - 24-7-2015 at 14:15
This project must be put on hold for now, most of my access to proper tooling is gone so I might not work too much on machining. But I'll keep it
alive on the back burner, scouting for what I need.
[Edited on 24-7-15 by Fulmen]aga - 24-7-2015 at 14:47
Unfortunately, it would likely be rather hygroscopic.
Ancient chinese proverb :-
Make Rocket in Summer.
Fart in tube.
Seal Tube tight.
No more atmosphere any self-respecting chemical want to absorb.Fulmen - 25-7-2015 at 03:25
Eutectic nitrates sounds like a good way to improve casting properties of sugar propellants. The K/HN4-mix is especially interesting if it improves
burn rate over straight NH4, although I have seen tests (20 years ago) that showed signs of reaction with the fuel when molten (liberation of gas).
Don't remember which fuel they tested though, could have been charcoal. deltaH - 25-7-2015 at 03:42
59 wt. KOH and 41 wt. % NaOH eutectic at 170°C. See US 20050072837 A1 patent application for this and others. HIGHLY dangerous of course!MeshPL - 20-8-2015 at 08:01
In my "chemistry tables" book I've found the following compositions, none of them being nitrates:
50% ZnCl2 + 50% KCl m.p=.230C
60% ZnCl2 + 20% NaCl + 20% KCl m.p.=203C
67% AlCl3 + 33% KCl m.p.=128C
And finally unbelievable:
60% AlCl3 + 26% NaCl + 14% KCl m.p.=94C (!)
I assume zinc and aluminium chlorides are not hydrates here.
Note that anhydrous zinc and aluminium chlorides cannot be prepared with aqueous HCl!PHILOU Zrealone - 20-8-2015 at 08:50
@Fulmen,
Just asking:
Is the corrosion of your steel pieces not a problem?
I suspect molten nitrate 200-400°C might be rude to them; so will chlorides... Fulmen - 20-8-2015 at 09:03
Corrosion shouldn't be a problem with nitrates. It will probably oxidize the surface, but it should only form a thin layer. sussyn - 21-8-2015 at 07:29
I have extra KNO2 if you're also interested in nitrite eutectics. Gotta check shipping costs etc, I'm not too experienced with the exept quantities
rules since ORM-D went away, but I'll be happy to learn. There might be some NaNO2 hiding somewhere, too, or I can get some.
Good luck!Fulmen - 21-8-2015 at 11:53
Thank you for the offer, but I think I'll focus on the nitrates for now. This whole project has been delayed as my shop access has been severely
restricted lately. But hopefully that will sort itself out during the winter, it would be nice to have this done by that time...Praxichys - 21-8-2015 at 15:59
Lithium salts aren't that hard to come by. Lithium carbonate can be had for about $12/lb. The carbonate is a great point to start making lithium
salts; all that is needed is to treat it with various acids.
That is a fair point, I'll look into that. The Volatile Chemist - 23-8-2015 at 14:03
I saw the same thing on continentalclay.com. 1lb pack. Not too bad price-wise.
Lithium salts
chloric1 - 4-2-2018 at 04:50
I have been trying to find the patent but no luck. Basically, the premise is if you start with lithium chloride and sodium nitrate( also
bromide,iodide etc), you would mix strong solutions of the two then raise temperature to reduce volume causing NaCl to drop out. You FILTER HOT and
keep reducing volume until another crop of NaCl drops out. Filter hot again. Now you have a strong lithium nitrate solution still contaminated with
sodium chloride and perhaps unreacted lithium chloride and sodium nitrate. No here is where it gets interesting. Lithium salts have an uncanny
ability to dissolve in polar organic solvents like methanol, ethanol, and acetone. So , as long as your lithium chloride is not in excess, you
should be able to add excess alcohol or acetone to salt mix to drop out more sodium chloride as this will shift the equilibrium in favor. Filter
again and evaporate your filtrate. Next to seal the deal, take crystal residue and dissolve in neat acetone or alcohol. This should virtually
eliminate any further sodium from the lithium nitrate.
This is tedious but cost effective as you would not handle nitric acid. Lithium chloride solution is easily generated by adding the pottery grade
lithium carbonate to diluted muriatic acid from home improvement store. Add slight excess of lithium carbonate to remove dissolved metals like iron
from acid solution. Hope this is helpful.byko3y - 4-2-2018 at 17:18
chloric1, dunno why you are thinking to mess with LiCl if you have Li2CO3 as a starting material. Solubility of lithium nitrate is
only slightly higher in alcohol and acetone than solubility of lithium chloride. In this way you will get a mixture of LiCl+LiNO3.S.C. Wack - 5-2-2018 at 13:23
Weird how so many mixtures are supposed to melt at 145C. Fieser says 10 parts KNO3 7 parts NaNO2. Others replace some K with Na: 53:40:7. Or nitrates
of K (65.8) and Ca (34.2). Even more Na for 142C: 44.2% KNO3, 48.9% NaNO2, 6.9% NaNO3 google says.
