AN APPARATUS FOR DETECTING SMALL CONCENTRATIONS OF ETHENE IN AIR

摘要

An apparatus for detecting small concentrations of ethene in air, comprising a spherical glass vessel, having a flat bottom with a window portion, and a radiation detector in front of said window with a radiation ineterruptor interposed therebetween. A gas mixing tube extends in said vessel opposite to said bottom towards the centre of said vessel. Near its outer extremity said tube is provided with a constriction for sucking inwards air to be tested and ozone produced in an excess amount by an ozone source, and for mixing said gas flows. An exhaust connection is provided near said mixing tube, and serves to remove gas by maintaining a small negative pressure differential inside said vessel. Inside said mixing tube the mixing of the gases is completed, and a chemoluminescent reaction between the ozone and the ethene in the air to be tested is completed within said vessel before the gas flow leaves said vessel. The radiation produced by said reaction is reflected by a reflecting coating towards said window and is transformed in a pulsating electrical signal corrected for the dark current of of said detector. The correction for the dark current can be improved by using a signal amplifier controlled by a signal with the radiation interruption frequency. Preferably the ozone is produced by an ozonizator comprising coaxial tubes between which a corona discharge is maintained.