Sciencemadness Discussion Board - Percise temperature non-toxic double boiler fluid?

Percise temperature non-toxic double boiler fluid?

freedompyro - 28-1-2012 at 01:44

I want a double boiler liquid that I can get to simmer at about 105C. I have some ethylene glycol that I could use to modify the boiling point of water...

40% H2O/Ethylene Glycol boils at 104C. Propylene glycol would take a while to get shipped.

Could I perhaps use a percentage of sugar in water or something else that is simple? It would be nice to have something non toxic that could give a good range of like 100-150C. It isn't too important that one part boils off before the other because you can just go a couple C higher and use a very light boil and prevent evaporation with aluminum foil.

Edit: I found this randomly on google... But it doesn't specify what concentration of salt!!!
"Water alone boils at 100 C and with salt it boils at about 104 C."

A 20% solution of H2SO4 boils at 105C... Now that's even worse than EG...

[Edited on 28-1-2012 by freedompyro]

Adas - 28-1-2012 at 05:14

When you make very pure water, and use very smooth containers, you can superheat the water up to 250°C, IIRC

But superheated water isn't really something I would mess with.

weiming1998 - 28-1-2012 at 05:23

Quote: Originally posted by Adas

When you make very pure water, and use very smooth containers, you can superheat the water up to 250°C, IIRC

But superheated water isn't really something I would mess with.

You can do that with a microwave, ordinary tap water (it doesn't need to be pure) and a smooth container. But temperature control is not exact. It will also spurt hot boiling water+water vapour when you touch the container. But maybe you might be able to work with it if you use a very long stick to tap the container when finished and wear protective clothes+goggles.

Neil - 28-1-2012 at 05:56

Take a look for phase diagrams of water with different salts. Do you have a thermometer? Start dumping things in water and probing them.

Also search for "boiling point elevation" and try to find a azetrope with safe additives that could give you a constant boiling point despite inevitable evaporation losses.

While I Strongly suggest Not using ammonium nitrate, if you look at its effect on the boiling point of water you would see it does what you want, but without forming an azeotrope (obviously).

Endimion17 - 28-1-2012 at 06:56

Superheated water? No. No and no. Just forget about it, ok?

Take a highschool chemistry book and check the chapter about colligative properties, section about boiling point elevation and depression, ebullioscopic constant.
Constants are easy to find, the equations are simple, easy peasy.

watson.fawkes - 28-1-2012 at 11:37

Quote: Originally posted by freedompyro

I want a double boiler liquid that I can get to simmer at about 105C. I have some ethylene glycol that I could use to modify the boiling point of water...

Your intuition to use what's essentially automobile radiator fluid seems just fine to me. In fact, just go to the auto parts store and use whatever they have. An exact formula isn't important for your application. It's a bit toxic, so don't drink it, but is otherwise rather benign.

freedompyro - 28-1-2012 at 13:57

I was under the impression that inhaling the vapor of it would cause poisoning.

entropy51 - 28-1-2012 at 15:29

Quote: Originally posted by freedompyro

I want a double boiler liquid that I can get to simmer at about 105C.

I have used CaCl2 to raise the boiling point of water baths. It would be relatively easy to get the boiling point to 105 C, but I don't know off the top of my head what concentration you need. Some driveway de-icers are pure CaCl2, Prestone is one brand if I remember correctly. The solutions are corrosive to many metals however.

freedompyro - 28-1-2012 at 18:00

Oh... I have a bunch of CaCl2.

Ill just add some and use a thermometer probe to adjust.

watson.fawkes - 28-1-2012 at 18:16

Quote: Originally posted by freedompyro

I was under the impression that inhaling the vapor of it would cause poisoning.

If you're using it as a double boiler, you shouldn't be getting much free vapor at all. The standard configuration acts much like a reflux boiler. As long as you're not pumping too much heat into the system, you shouldn't be getting much boil-off at all.

If you're trying to use a solution as a thermostat, relying on the physical properties of the medium to regulate temperature, you'll need to capture the vapor and condense it anyway, since any composition is going to drift as water evaporates unless you find a combination whose azeotrope temperature is right at the point you're trying to maintain.