Will food coloring dye liquid nitrogen?

Originally published at: http://boingboing.net/2017/05/26/will-food-coloring-dye-liquid.html

“When he’s underwater does he get wet?
Or does the water get him instead?
Nobody knows, Particle man”


I would guess no.


I suspect you’re right.
Almost all food colourings require polar solvents. Liquid nitrogen is a nonpolar solvent (as it has to be since it is diatomic and contains only one atomic species). Even fat soluble dyes are polar because actual fats normally have one end polar. One would expect the colouring not to dissolve, and if a carrier is present - such as isopropanol - that would freeze.
I’ve never tried it, but it would be interesting to see what colour you get if you dissolve bromine or iodine in liquid nitrogen - if you can.

edit - error fixed


And the fact that the pigment in the food coloring is already dissolved in water would mean that the water would just freeze. One suspects that there ARE pigments that would dissolve in liquid nitrogen, but food coloring isn’t the place to find one. And you probably want to start with a powdered pigment, because pigment already dissolved in a substance that has a melting point higher than the boiling point of nitrogen is not going to work.


Nitrogen is non-polar, as opposed to water. I assume that the food colorants used in this video are all water-soluble, so them not dissolving into the liquid nitrogen seems logical. It’s like trying to mix oil with water. Next time he needs to try to dye liquid nitrogen using oil-based pigments. They might give the liquid some hue. (Surely, Bob Ross would recommend Van Dyke Brown)


Although I can’t think of a counterexample, and there may not be any, I’m tempted to quibble with that second part, because it assumes you need different species to have a nonzero bond dipole moment, which is not strictly true, I mean how would propyne feel to hear you say that.


Corrected. Though I don’t understand the reference to propyne since it has two atomic species.

Honestly, I don’t know what you’re talking about. That’s beyond me.

I was simply thinking that since food coloring is a water-based dye, it would freeze then it touched liquid nitrogen.

I wonder if you could temper it with intermediate liquids first. Dissolve it in alcohol first, then pour that into the nitrogen, kind of thing. Alcohol stays liquid to -114C, LN is -196C. Might need an intermediate stage, something liquid at -114C and -196C.

@Arduenn has explained it above.

Do you need to? If you have the dye as a solid, it may simply dissolve directly. Caffeine, after all, dissolves in liquid carbon dioxide (which is how coffee is decaffeinated).

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It does, but the CH carbon is more “electronegative” than the CH3 carbon. I think you could come up with a pure allotrope of carbon, or maybe boron or sulfur, where some atoms are permanently more “electronegative” than others.

Or to look at it from another angle, if H, N and O all had the same electronegativity, you could still account for why ammonia and water are polar (they have lone electron pairs sticking out on one side). That is, electronegativity is not so much a fundamental property as an empirical aid to account for the complicated stuff that molecular electrons actually get up to.

Anyway, on reflection, a more concise form of my previous post would have read “ozone is polar”.

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HCl begs to differ.

I know. And I still don’t get it.
I was never good at chemistry.

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@Arduenn was responding to my post, in which I eventually wrote
"as it has to be since it is diatomic and contains only one atomic species"

There’s a lot of confusion going on here as a result of my originally missing out “is diatomic and…”

Propyne fails my test because it’s a hydrocarbon; HCl has two elements also. Ozone is triatomic.

Liquid nitrogen, however, which is what we were discussing, is N2 and is nonpolar averaged over any significant time interval and assuming that none of the nitrogen atoms are in some weird quantum state, or some other physical state which I don’t know about. Or shall we say that it’s many times less polar than a water molecule? Or shall we just give up the whole thing and agree that if the dye is dissolved in isopropanol it’s going to freeze on contact and probably only escape, if at all, in a longer time frame than the experimenter can be bothered to sit around watching it unless he or she is the person who set up that experiment in which a lump of pitch slowly flows under gravity thus making watching paint drying look like an exciting, dynamic activity? Or something? His hat, his hat!

Good point. I only skimmed over the posts, as the nature of N2 seemed obvious enough to not warrant a lot of discussion in the first place.

There, removed the diatomic part, not to get ourselves off on a totally irrelevant tangent.

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