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Mixing the Unmixable
markthebrewer writes "From an article in the New Scientist: Conventional wisdom every 15 year-old knows says that you can't mix oil and water without some kind of surfactant. However a team lead by Richard Pashley from the Australian National University in Canberra have done it simply by first removing all dissolved gases from the water. Apart from the obvious potential improvements in salad dressings, it could have an impact on the manufacture of everything from drugs to paint - anywhere an emulsion is required. Apparently, it will also give some insight into the mysterious 'long-range hydrophobic effect' (or why oil droplets coalesce over surprisingly long distances)." Keep in mind the usual scientific caveat: this experiment doesn't seem to have been replicated by other experimenters yet.
What the environmental impact of water based oils will be.
From the article...
An alternative might be to disperse the medicine in degassed water, which is already produced on a large scale by the oil industry.
You're telling me the oil industry itself makes degassed water on a large scale - for some unmentioned reason - and didn't discover this researcher's claims that oil and degassed water spontaneously emulsify? What's up with that?
---If you can't trust a nerd, who can you trust?
how exactly is "mixing" defined? If I put olive oil and tap water in my blender, and crank it on high, it is pretty well mixed, at least temporarily. Is it critical that the "mixture" stay "mixed" over time?
"And this is my boy, Sherman. Speak, Sherman." "Hello." "Good boy."
The oil-water mixture is probably also a metastable state. In the presence of any catalysts (in this case dissolved gases; in the case of biological systems this function could be taken over by proteins, salt ions, I-don't-know-what-else...) the oil molecules would condense and clot together. Oil droplets are thermodynamically stable only above a certain droplet size; the same is true for water droplets in the case of the supercooled gas. Without catalysts, the critical droplet size cannot be achieved.
Geeks note: Brominated vegetable oil is also an ingredient in Mountain Dew, and probably other of your favorite flavors of synthi-caff.
Breakfast served all day!
You folks are missing the key point in the article:
"The mix spontaneously formed a cloudy emulsion".
This is very different from the usual case where you take an oil and water mix and maybe some surfactant and agitate it.
The reason is that the formation of surface area during the dispersion of oil into water normally requires an energy input. Surfactant reduces the energy required and also often stabilizes an emulsion by adding some repulsive forces (either steric or electrostatic) between the droplets. However, with the exception of systems called microemulsions that increased surface area always represents a energy increase. With time (the amount of time depending on the use of suractant etc.) that free energy will cause the emulsion to break and form two homogeneous layers.
Microemulsions are the exeception; they are unusually favorable systems that reduce the energy of formation of surface area to near zero, probably less than the thermal energy kT available. Thus they can spontaneously form emulsions that are stable indefinitely. Microemulsions generally require very specific compositions to form so they are not often seen except in some specialized applications.
The problem with Pashley's work is that he is claiming the spontaneous formation of an emulsion.. This would normally be expected only if the surface energy of his mixture was near zero - and there is nothing in the description of this system to indicate that this is happening, regardless of the side show with air bubbles.
What is more likely is that his oil-water system actually contains some small amount of surfactant as an impurity (quite typical in many oils). If so, the process of lowering temperature will take this mixture through what is known as the phase inversion temperature, where the mixture will achieve a minimum surface tension. This lowered usrface tension will make formation of an emulsion with minimal energy input quite likely.
> It's gut wrenching that we're creating a generation that prides itself on its stupidity.
You should read this article featured on /. lately. It gave me some thoughts about why teens are willing to be stupid.
methodology: I boiled a cup of water in the microwave. I waited for it to cool, and boiled it again. I let it cool and boiled it again. I carefully removed the cup and let a few drops of (extra virgin olive) oil drip onto the surface from about 1cm height to minimize air bubbles.
observations: the oil stayed in a tight slick on the surface for about 10 seconds. Then it spread out, I'm assuming because of the heat of the water.
After a about 45s, a piece of wood was introduced to the water, which caused mild boiling suggesting that the water had indeed been devoid of air.
After more than 30 mnutes, the slick was still on the surface without mixing.
Conclusions: those guys are need to accumulate more data.
Bruce
Bruce Perens.