GB919759A - Liquid analysis apparatus with closed flow cell - Google Patents

Abstract

<PICT:0919759/III/1> <PICT:0919759/III/2> In the analysis of a flowing liquid in an automatic colorimeter wherein the flowing liquid is segmented by the introduction of air or an inert gas thereby to cleanse the walls and minimize sample contamination, the sosegmented stream is passed through a passageway bearing a suction pipe which removes the gas segments before the liquid passes through the colorimeter cell. In the Figures the liquid to be analysed is introduced by pump tube 38 and the air or inert gas by pump tube 40. The two streams merge at fitting 32 after passage through conduits 34 and 36 respectively, and the segmented stream flows through conduit 42 where it joins a stream of processing liquid or colour reagent flowing in conduit 44, the processing liquid being introduced into the system by way of pump tubes 46 and 48 and conduits 50 and 52 and being mixed in helical mixing coil 56. The treated segmented stream then passes through conduit 58 to helical mixing coil 60 where the liquids in each of the segments L are mixed with each other. The segmented stream passes to separating device 62 (Fig. 2) where the air segments are aspirated through tube 72; the liquid passes on to blender 76 and enters the colorimeter cell 18 at 26 and leaves at 28. The analysis is based on the visible light transmittance of the sample in the cell, the degree of absorption of the light by the liquid being measured by a photo-electric device. Pump 12 may be of any suitable type, it may comprise platen 82 and flexible pump tubes 38, 40, 46, 48 and 72 which are simultaneously compressed progressively along their lengths by the longitudinal movement of transverse pressure rollers 84. The apparatus can be used for the continuous analysis of a series of samples or for the analysis of a continuous liquid stream, e.g. it can be used for determining the chloride content in boiler feed water. The boiler feed water is continuously supplied to 38, air is supplied to 40, a 6% solution of ferric alum to 46 and a saturated solution of mercuric thiocyanate to 48. The colour of the stream is measured in cell 18 and the results recorded on recorder 16. Specifications 774,711, 817,070 and 839,649 are referred to.