DURAN® Bell Jar, with glass knob topDURAN Bell Jar, with glass knob top, 185 mm By default, tests are carried out at normal pressure. The conduct of tests under vacuum (negative pressure) can have significant effects on the reaction sequence. In order to be able to observe these effects in the rough and fine vacuum range, a vacuum experiment plate and a bell jar (also called air pump bell) are required. Features and Benefits: The button makes it easy to raise the bell jar Fired on,