[Babcock_Hall]

Whiting DA and Gill GB, Aldrichimica Acta, Vol. 19, No. 2, 1986
https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/marketing/global/documents/221/758/acta-vol19.pdf

"An inflated balloon can be used to main­ tain an inert atmosphere for a short time. The set-up shown in Fig. 6 is particularly convenient; when attached to the ap­paratus, the two-way Y-neck allows evacuation, balloon inflation and connec­tion of the balloon ballast to the reaction flask. Since the apparatus is pressurized, joints should be held together with spring clips. The inflated balloon gives a false sense of security, since it would appear in­ conceivable for 0₂, CO₂, or H₂O to diffuse into the system against the internal pressure. However, the rates of permeation of thee gases through the ca. 0.013-cm balloon membrane depends upon the difference in their partial pressure on the two sides of the membrane.  The internal pressure exerted by the inert gas is irrelevant.  Simple calculation using standard permeability data(1) will provide an estimate for the extent of intrusion for a given system."

The conclusion that the authors reach is that 5-minute tasks are fine for balloons filled with an inert gas such as nitrogen.  However, contamination of the gas happens within an hour.  Thoughts?

[hollytara]

Anyone use metallized mylar balloons instead?

The better way is always to have a gas line with a bubbler.