“Many scientists are going to find this very hard to believe,” says colloid scientist Len Fisher of the University of Bristol in England, “but Pashley has provided very strong proof that oil and water will mix.” Pashley’s observation is bound to cause controversy as the reason it happens is still unclear. Chemists are waiting to see whether the experiment can be repeated. If confirmed, the finding could provide clues to one of chemistry’s most puzzling phenomena. This is the so-called long-range hydrophobic force, which causes oil surfaces to attract one another over what to chemists are remarkably long distances.
The effect prevents oil’s dispersion in water, and means that you can only make oil and water emulsions, such as French dressing for salads, by shaking them and adding stabilising agents. But although countless chemists have measured the force, no one has ever been able to explain how it works. Pashley was studying oil-like hydrophobic surfaces as they were being pulled apart, and spotted microscopic cavities appearing on their surfaces. Water that has been exposed to air contains the equivalent of several teaspoonfuls of dissolved gas per litre, and Pashley suspected that the cavities contained bubbles of gas that had been drawn out of the water, maybe as a consequence of the long-range hydrophobic force. To test his hunch, Pashley removed almost all the gas from a water-oil mixture by repeatedly freezing and thawing it while pumping off the gases as they evaporated out ( Journal of Physical Chemistry B , vol 107, p 1714). The result suggests that dissolved gas may be involved in how the force acts. “He takes the air out and he doesn’t get the long-range hydrophobic force. It doesn’t nail the hydrophobic force down, but now we have something to work on,” says James Quirk, a chemist at the University of Western Australia in Perth, who hopes that studying the spontaneous emulsions may lead to an explanation for the elusive force.
Even more surprisingly, the mixture did not break up even when gas was put back into the water after the emulsion had formed. Pashley suggests that the gas might interfere with the hydrophobic force most effectively only when the oil droplets are extremely close together, such as when they are first separating as the emulsion starts to form. Once the emulsion has formed, hydroxyl groups from the water adsorb onto the surface of the oil droplets, making them similarly charged and thus preventing them from coming close together. If spontaneous emulsions can be made at will, they could have important applications in medicine and the chemical industry. Many injectable medicines are currently only soluble in oil. An alternative might be to disperse the medicine in degassed water, which is already produced on a large scale by the oil industry. Emulsion paints, which currently use chemical stabilisers to stop them separating, could also be made more cheaply if degassed water would do the trick. Our commitment to addressing racism: We're taking steps toward real change. Senior shopping event: Each Tuesday, those age 60 and older can shop the store and Pharmacy one hour before opening. Coronavirus: What we're doing to prioritize your health. Everything you need is available with Walmart Pickup. Everything you need is available with Walmart Pickup. Plan your visit, find store services and get the best values — it’s your helping hand in the store. You will receive an email shortly at: Here at Walmart.com, we are committed to protecting your privacy. Your email address will never be sold or distributed to a third party for any reason. Due to high volume, we can't respond to individual comments. Your feedback helps us make Walmart shopping better for millions of customers. Your feedback helps us make Walmart shopping better for millions of customers. We’re having technical issues, but we’ll be back in a flash. Serving the Carolina's since 1974, Team Charlotte Motorsports is Charlotte's go to powersports dealer and the oldest franchised dealer! With almost 50,000 square feet and over 450 motorcycles, scooters, dirt bikes, side by sides, personal watercraft and ATV’s in stock, we have the selection you are looking for, all built and ready to ride. Looking for a new Honda, Kawasaki, Suzuki, or Yamaha? We are not a catalog dealer, we stock them deep so you have the selection you want.
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