Russell,

On Fri, 12 Mar 2010 04:13:32 +1300, Russell McMahon wrote:

>... 
> The important implication for me is the (utterly obvious now) fact
> that you CANNOT stop a given gas diffusing by "balancing" it with
> anything on the other side.

Indeed, and I've observed this with CO2 dissolved in liquid vs. present in the gas above it (ie a bottle of Coke which isn't full).  You can buy a little pump fitted to a 
lid which you put onto the bottle, and give a number of squeezes, increasing the pressure in the bottle by adding air.  It's sold as preventing part-empty bottles 
losing their fizz, but the result is as expected from what you say above - it's completely useless!  Note that there is no membrane, just the liquid's meniscus, but I 
think the principle at work is the same.

I wonder if I could bring a case under the Trades Descriptions Act, or the Sale of Goods Act, because the the device doesn't do what it's being sold for?

Cheers,


Howard Winter
St.Albans, England


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