Abstract: An improved sight glass for use with sampling systems employed for testing the content of chemical reaction vessels. In addition to incorporating a check valve for preventing contamination of a vacuum source, the device incorporates provision for entrapping and draining sampled fluids in the event of leakage or fracture of the glass components thereof. This is accomplished by providing an inner transparent glass tube, the inner surface of which is chemically inert, and an outer concentric tube of synthetic resinous material which surrounds the inner tube and is less subject to breakage. The cylindrical interstice between the inner and outer tubes forms a drain for retaining leakage caused by fracture of the inner tube. A floating valve cooperates with a valve seat positioned longitudinally medially of the inner and outer tubes.

Abstract: A rapidly demountable structure for supporting electronic probes within a reactor vessel at the inner end of a dip tube element. The structure includes a fixed dip tube element which is permanently positioned in a recess at the inner end of the dip tube, and a probe supporting element selectively engaged with the dip tube element through a bayonet type interconnection. A damaged probe is replaced by first disconnecting the probe supporting element from the dip tube element, and disassembling the probe supporting element to permit removal and replacement of the probe. Means is provided to seal the opening to the reactor vessel during the period in which the probe supporting element is in disengaged condition thus affording safety to service personnel during replacement of the damaged probe.