| 摘要 |
A flexible plastic bag is suspended from the lid of a rigid cylindrical vessel. In the side wall of the bag, near its top, is an aperture covered by a gas-permeable liquid-impermeable membrane. Suction is applied to space between the vessel and the bag so as to draw liquid into the bag. The membrane shuts off fluid flow therethrough when the liquid drawn into the bag covers the membrane. The lower portion of the vessel closely surrounds and supports the lower portion of the bag, whereas the upper portion of the vessel side wall is enlarged so as to provide clearance outwardly of the membrane.
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