text: A filter tube for a reaction or other fluid vessel is disclosed which maintains the vessel under an inert gas atmosphere and maintains the integrity of the inert gas seal while performing filtered or unfiltered filling or filtered draining operations. The invention uses an air gap between the vessel opening and the top of a filter tube which allows pressure equalization within the vessel during the filling and draining operations. Pressure equalization prevents the loss of liquid during heating operations and permits the use of higher pressure atmosphere within the vessel. The invention can be used for a number of laboratory and clinical operations on a variety of size and shape vessels. A vessel with this filter tube is very well suited for use in laboratory automation systems including automated solid phase chemical synthesis, biological screening and other procedures known to those in the scientific fields.
  When performing solid phase chemical synthesis or other chemistry, clinical or biological fluid handling operations, it is desired to have a fluid containment vessel with the following features: chemically inert, controlled atmosphere and temperature, capability for mixing, inlet port for fluid addition, fritted outlet port for waste and product drainage. The vessel must also be compatible with as many automated systems as possible, as there is a clear trend toward automating as much laboratory work as possible.
  In considering the design of such a vessel, the inlet and outlet ports, used for fluid addition and removal, are critical features. The integrity of the inert atmosphere and solid support retention are dependent upon proper design of these ports.
  In some vessel designs, fluid enters the top of the vessel and drains out the bottom of the vessel through manually operated valves. Solids are maintained inside the vessel by means of a frit at the bottom of the vessel. The frit serves as a filter which allows for the passage of fluid and the retention of solid materials. This type of valving arrangement is suitable for a small number of reaction vessels but is not practical for automatic filling and draining of a larger array of vessels because both a top and a bottom valve are required for each reaction vessel. In addition, every valve added to a system decreases reliability and increases the chance for contamination of the reaction mixture.
  What is needed is a vessel which does not require valves or a u-tube system and which will allow for the delivery of liquids, slurries and gases which can be stirred, mixed, heated, cooled and other wise reacted. Further this vessel must be capable of maintaining an inert or reactive atmosphere and must protect against leakage or spillage of its contents.