Sciencemadness Discussion Board

Making the most dense solution possible - that doesn't react with Cu or Al

RogueRose - 5-4-2019 at 20:04

I'm trying to find some salts that are capable of making a "high density" solution and the ideal solution would not be reactive with copper, aluminum and iron/steel (though steel not as necessary).

I was looking through different salts and it looks like calcium and ammonium nitrate both have a pretty high solubility but I don't know how that would effect the density of the solution.

Anhydrous calcium nitrate - density 2.5g/ml
2710g/L @ 40C

Ammonium nitrate (density of 1.725g/ml) is listed at:
2970g/L @ 40C
4100g/L @ 60C
10240g/L @ 100C

40C is a good temp, Ideally it would be a little lower, closer to room temp, but I can work with 40C

Now comes the part I get confused with and that is calculating density b/c I'm not sure how all this comes together and I'll use the extreme NH4NO3 @ 100C as an example.

Does 10240g/L mean that 10kg of AmNit dissolves into 1L of water, which is what I recall being how that works? It doesn't mean that everything dissolved remains in a liter of space.

10240g / 1.725 (density of dry AmNit) = 5,936ml
1000g = 1000ml water

11,240g / 6,936ml = 1.62g/ml

If the above is correct, then Ca(NO3)2 would be:

2710g / 2.5g = 1,084ml
1000g = 1000ml water

3710g / 2084ml = 1.78g/ml (CalNit tetrahydrate is 1.89g/cc - so that seems possibly correct)

So I'm guessing after seeing these numbers that it's going to be pretty difficult to get a high density solution unless I find a highly soluble salt that has a heavier metal - possibly iron or copper but I thought those might react with the aluminum.

Does anyone know of a solution that can be made that would have a density near 2.7g/ml?

[Edited on 4-6-2019 by RogueRose]

[Edited on 4-6-2019 by RogueRose]

DraconicAcid - 5-4-2019 at 20:33

Does the solution have to be aqueous? Bromoform and tribromoethane have densities in that area, and you could mix the two to get almost exactly the density you want.

If it has to be aqueous, then you'll want heavier atoms in the ions. Something like cesium iodide, for example (but I can't find the density of that particular solution at the moment).

[Edited on 6-4-2019 by DraconicAcid]

RogueRose - 5-4-2019 at 21:21

Quote: Originally posted by DraconicAcid  
Does the solution have to be aqueous? Bromoform and tribromoethane have densities in that area, and you could mix the two to get almost exactly the density you want.

If it has to be aqueous, then you'll want heavier atoms in the ions. Something like cesium iodide, for example (but I can't find the density of that particular solution at the moment).

[Edited on 6-4-2019 by DraconicAcid]


Wow, those are impressive. Thanks. I should have said that it would be best if the solutions were fairly benign, meaning as little vapors, toxicity or flammability as possible. I'm guessing this might be a tall order, but I thought I would see if anything such as this existed.

crystal grower - 5-4-2019 at 22:36

Is the ammonium nitrate really 10g/mL at 100°C? That seems a bit too much to me.

Metacelsus - 5-4-2019 at 23:14

Yes it is. However, that's not 10g/mL solution volume, it's 10g/mL water. So the actual density of the solution will be less than that of solid ammonium nitrate.

crystal grower - 6-4-2019 at 01:35

Oh, of course... I didn't notice it was solubility data, not density.

Tsjerk - 6-4-2019 at 04:43

I sell cesium-chloride. I have about 600 grams left. Goes up to 1850 g/l.

link

Plunkett - 6-4-2019 at 06:58

Why do you need the solution to not react with aluminum? Is there another metal you can use or could you coat the aluminum with something less reactive?

If not reacting with aluminum is a requirement then I can think of three solutions: calcium bromide, caesium formate, and lithium/sodium polytungstate. CaBr2 solutions start out with a specific gravity of 1.7 and can be increased to 1.8 with the addition of CaCl2 (source). I do not know what temperature these densities are quoted at so the solution might be even denser at higher temperatures. Caesium formate would be a lot more expensive/harder to get, but it can get up to a specific gravity of 2.4 (source). Lithium/sodium polytungstate solutions have a specific gravity of ~2.9 at room temperature, but they also have a high viscosity and may be difficult to obtain (source)

If the solution can react with aluminum then you could use Clerici's solution, a mixture of thallium formate and thallium malonate which gets up to 4.25 at 20°C, although this has the drawback of being exceedingly toxic (source). There is also zinc bromide solutions with a SG of 2.5 at 20°C (source). Last, and this is just an idea, is indium (III) bromide. I cannot find much documentation on it, but InBr3 has a solubility of 571 g/100 mL of water at 20°C (source). If you assume volume additivity like you did in your ammonium and calcium nitrate calculations, a saturated InBr3 solution would have a specific gravity of 3.0.

I do not know where you are getting your solubility data from, but Wikipedia has a solubility table which lists the solubility of several different compounds in water at different temperatures in a easy to read format: https://en.wikipedia.org/wiki/Solubility_table

[Edited on 6-4-2019 by Plunkett]

clearly_not_atara - 7-4-2019 at 15:59

Pumukli: I get the impression he's trying to gravimetrically separate aluminium powder from denser contaminants. Possibly, copper.

Caesium tungstate is reported to form a solution that floats diamond. It should be less dangerous than thallium salts.

http://en.wikipedia.org/wiki/Caesium_tungstate

Additionally, Wikipedia reports a stunningly high solubility of 551g / 100 mL for silver perchlorate:

http://en.wikipiedia.org/wiki/Silver_perchlorate

but this will certainly oxidize aluminium, and may cause an explosion.

[Edited on 7-4-2019 by clearly_not_atara]

Fulmen - 7-4-2019 at 22:00

CNA: That's my guess as well, separating chips/turnings. And me thinks he be boned, it's probably going to be either too expensive or too hazardous. Something like lead or bismuth oxide suspended in oil could work for larger objects, but probably not for fine turnings.

I would consider magnetic separation.