Abstract: A double tube sealed sampling device adapted to be incorporated into a dip tube for sampling the contents of a chemical reactor on a continuous or intermittent basis. In a preferred form, the device may be maintained in a sealed relationship to the reactor to avoid any contact with the contents of the reactor with the outside environment. In installed condition, the two tubes which are of relatively small diameter are shielded from turbulence within the reactor by the larger diameter hollow cylinder of the dip tube, thereby permitting the smaller diameter tubes to be formed from unreinforced polytetrafluorethylene (PTFE) or similar material.