What is/are the properties of a liquid (e.g. viscosity, surface tension) which is conducive to formation of stable bubbles floating in air (not the bubble inside the liquid)? E.g., if soap dissolved water is bubbled through a straw, big-small air bubbles are formed which comes out of the liquid and keep floating in the air.

This Wikipedia page (http://en.wikipedia.org/wiki/Surface_tension#Surfactants) attributes this to low surface tension of the liquid, but I can enumerate several liquids like spirit, petrol which have quite low surface tension, still if you blow through a straw into it, you won't get bubbles.

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    $\begingroup$ There are so many links You will find in the net when You search for "soap bubbles"! $\endgroup$ – Georg Jun 18 '11 at 10:08
  • $\begingroup$ Maybe you misunderstand how surface tension acts. In order to get bubbles you need relatively large surface tension (think of a party balloon for an extreme). The lower the surface tension, the less bubbles, because there will not be enough elasticity to sustain a surface against the internal air pressure. $\endgroup$ – anna v Jun 18 '11 at 18:43
  • $\begingroup$ Water has higher surface tension than soap dissolved in water, yet water doesn't form bubbles, soap solution does. Mercury is a liquid (at room temperature) with very high surface tension, do you think it can form bubbles? $\endgroup$ – pongapundit Jun 19 '11 at 5:06
  • $\begingroup$ Nowhere in the wiki link you give there is mention that low surface tension contributes to the creation of air bubbles. Could you give the quote so I can find it? Searching for "low" does not uncover such a statement. $\endgroup$ – anna v Jun 19 '11 at 5:11
  • $\begingroup$ you are correct that water has higher surface tension than a water-soap solution. See my answer. $\endgroup$ – anna v Jun 19 '11 at 5:20

OK, here is a complicated and clear explanation of what you are asking, which is also new to me: Soap is a complicated chemically molecule it breaks the high surface tension to allow bubbles, and also once in the air part of it protects the bubble from evaporation.

So it is an interplay between two components: surface tension and, as Georg points out,amphiphilic effects . It is not just the lower surface tension that creates bubbles, so for the other liquids you list an additive should be found that would work the same way soap works for water, not allowing evaporation.

  • $\begingroup$ "Soap" is not hydrophobic! Mineral oils/spirits are hydrophobic. Tensides are amphiphilic! $\endgroup$ – Georg Jun 19 '11 at 9:39
  • $\begingroup$ @ Anna , Look here: en.wikipedia.org/wiki/Agnes_Pockels $\endgroup$ – Georg Jun 19 '11 at 10:36
  • $\begingroup$ Thanks Georg, I copied the term from the link sloppily, it says: "At one end of the chain is a configuration of atoms which likes to be in water (hydrophilic). The other end shuns water (hydrophobic) but attaches easily to grease" I will edit. $\endgroup$ – anna v Jun 19 '11 at 17:11

It has to do with the properties of surfactants at interfaces, an internet search for that may shed some light on the solution.

  • $\begingroup$ Down-votes and no comments. Too bad of these users... @lindswait: Hello lindswait... Perhaps, this would be better if it's posted as a comment or just wait until you score 50 so that you could earn the privilege. This answer doesn't add any kind of information to the question..! $\endgroup$ – Waffle's Crazy Peanut Sep 30 '12 at 7:45

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