[tgardner01234]

My entirely random interest came from washing up and noticing that when you put sometimes only the smallest drop of washing up liquid (lets say, Fairy Liquid washing up gel/liquid) and put water on it it foams up to an immensely large degree and continues to foam for a very long time. When you try to rinse the foam out it takes forever - this interested me.

The question I wondered was is ----- how much foam is/can be produced from, lets say, 1 mole of washing up liquid.
After looking up the contents it seems the foaming ingredient is Sodium Laureth Sulphate/Sulfate, and I imagine we would have to write an equation for the reaction between SLS and whatever makes it foam (water and/or oxygen I guess) forming whatever it is exactly that foam is.. I imagine an oxide of SLS or.. I really don't know. Once we do that I imagine (a lot of imagining) that we can calculate a molar relationship between the foam and the SLS.

I would even appreciate just an idea of what you imagine could be theorised to calculate this. It just... came into my mind and massively puzzles and interests me now.
any ideas and help would be hugely appreciated.
(I don't know if all my 'i imagine' information is correct, so please, if in your answer you want to use different information PLEASE do)

All the best - thanks in advance

[jcaron2]

Tgardner, I have very little in the way of information to give you; I just wanted to commend you for being so inquisitive. If not for highly inquisitive people, we'd probably still be stuck in the stone age. :)

I will point out that if you want to figure out how "much" foam you'd get, you may have to collect a volume of foam and weigh it to get the density. Since, macroscopically speaking, it's neither a liquid nor a gas I doubt you'll be able to just look up a value for the density. Also, since it's so light, the mass of the air it displaces will not be negligible. In other words, you'll need to account for its buoyancy when you convert from weight to mass. In any event, you should be able to calculate the mass of foam (assuming you find the appropriate chemical equation) and then calculate the total volume of foam using the density.

I'm guessing that when Jerry (unknown008) wakes up from his island home in the Indian Ocean in a few hours, he'll be able to tell you the exact reaction (and whether it's purely chemical, purely physical, or otherwise).

[DrBob1]

Soaps and detergents are "Surface Active Agents" (surfactants). They are characterized by the presence of both water repelling ("hydrophobic") and water loving ("hydrophlic") segments in the same molecule. They cluster at the surface of immiscible liquid mixtures (oil / water) or gas / liquid boundries. The water/air boundary is a foam. The foam forms because the surfactant greatly lowers the surface tension of the water.
The surfactant can have a highly variable structure: the hydrophobic chain can be longer or shorter, branched or linear, aromatic or aliphatic. Etc; the hydrophilic portion can be cationic, anionic or nonionic. In other words a surfactant can be tailored to optimize a number of desirable characteristics or to minimize undesirable ones. This often depends on the intended use - shampoo wants lots of foam, laundry detergents want much less. (By the way, foam is measured by volume -- put a mixture in a graduated cylinder, shake the snot out of it and see the volume and persistence of the foam.) I would think these characteristics would be measured and graphed rather than calculated from an equation.
I hope this gives you some food for thought.

[jcaron2]

Sorry, I should have mentioned DrBob, as well, since he's the real chemistry guru around these here parts. No disrespect intended!

[tgardner01234]

Thanks both of you for those interesting answers - I very much appreciate those thoughts. I'll be sure to give that experiment a shot!

[Unknown008]

Aww... couldn't rep you DrBob :(