Seal-breakers, magnetic

Some items not usually described in elementary glass blowing texts, but frequently useful in vacuum apparatus, are magnetic seal-breakers, universal joints, and metal wire seals. Therefore their construction is described here. 

Fig. 1.2. The construction of a magnetic seal-breaker. A iron core or bundle of nails, B ceramic wool (asbestos substitute). For details see text.

The ampoule A was charged with the crystalline monomer, a phial P of initiator (e g. PFj solution), and a magnetic breaker M and then sealed at B to the rest of the rig which was then evacuated. Methylene chloride was distilled in from a reservoir on the vacuum line to dissolve the monomer and was then pumped off slowly, and evacuation was continued for 8 h, which process produced an efficient final drying. The purpose of the two pumping ducts C and D is to circumvent the evacuation obstacle presented by the sintered filter S. The required volume of solvent was then distilled into A, the rig sealed off from the line at E, and the ampoule A brought to the right... 

Fig. 5.11. Vacuum reactor for chlorination of metals. A Reaction vessel (100 ml) B beryllia crucible containing titanium metal C silica cradle D crucible support also serving as evacuation duct, and finally sealed off at the top at E F capillary tube G duct for breaker H appendix containing liquid chlorine J fragile capillary tip K weighted glass breaker L glass-coated magnetic retainer.

A magnetic breaker is inserted in the side arm B, and the vessel is attached to the vacuum line and evacuated. The lower portion of the apparatus is cooled with liquid nitrogen and the break seal is opened. Because the sudden release of hydrogen pressure into the vacuum line can sometimes propel the breaker upward with considerable speed, it is advisable to cushion the upper surface of the inlet port with glass wool to avoid possible breakage. 

As with other reaction calorimeters, it is sometimes necessary that adiabatic calorimeters should be sealed. Palkin et al, used a rubber membrane in the lid which provided a seal but permitted manipulation of the ampoule breaker attached to it the contents were stirred magnetically. 

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