> I imagine if someone invented a bottle cap that integrated a little
> CO2 cartridge (perhaps the small ones used for pellet guns) it'd work
> very well at keeping the drink fizzy.

Small pellet gun catridges started life as soda siphon propellant systems :=
-).

> But pressurizing it with room air isn't going to help that much,
> unless you're looking for dissolved nitrogen rather than dissolved
> CO2...

As per my previous comments, ratio of partial pressures will settle
down to ratio of molecular weights. If we assume O2, N2, CO2 are the
only gases present, then the molecular weights are ~=3D 32, 28, 44 for
N2, O2, CO2
SO CO2 will assume a 44/104 ~=3D43% of total pressure partial pressure.

Original pressurisation is probably 50 psi plus - maybe rather more.
1.5 l Bottles start getting dimensionally unstable as you approach 100
psi but are good for 150 psi + before 'self destructing'. =A0At 100 psi
in the bottles gas space and lots of O2 and N2 available the CVO2 will
settle down to ~ 43% x 100 psi =3D 43 psi. That's not TOO bad. The
amount of gas in the liquid will depend on solubilities - I won't go
and look them up but I think CO2 is very substantially more soluble
than the other two. The tendency to corm weak acids with water
(hypochlorous acid?) helps.

So pressurisation at 100 psi with air may well result in OK fizziness reten=
tion.

Small bottles can be pressurised higher safely - about in the inverse
of diameters as wall thickness is about the same in each case - BUT
one cannot be suire about the hoop stresses in the neck area and
attempts to pressurise very small bottles to 300 psi + WILL result in
your mileage varying. Do not do this at home, or, at least, not INSIDE
your home. A 1.5l bottle is very very very loud when this happens -
noticeably so initially if standing within about a metre. Immediately
after that everything may seem extremely quiet for some minutes. Eye
protection is a good idea [tm]. Ear protection can help.

If the bottle survive the fizziness retention treatment opening the
bottle becomes problematic :-).
My preferred method has been to invert the bottle and, having
pre-added fins and a nose cone, release the pressure suddenly.
By this stage the Coke or Pepsi in the bottle has usually been
substituted with water s the black stuff tastes better than water
(some say) and the water makes less mess.

1.5l bottles can leave the vicinity at up[wards of 100g. Try not to
have body parts in the bottle's path - at least until all liquid has
exited. This happens in a few hundredths of a second and an
unconstrained bottle is by then perhaps =A0few metres from the point of
pressure release.

The contents will now be MUCH less fizzy and also extremely spatially
distributed. Drinking them will be difficult although, if standing
nearby, a remarkable proportion seems to end up on ones person.

Slow release may keep the fluid more fizzy but may also result in some
violent results if eg Coke is being used.


=A0 =A0 =A0 =A0 =A0Russell

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