Sample monitoring instrument for on-line application

In a chemical analyzer device for determination of a characteristic of a liquid process stream by wet chemical analysis to enable control of the process, said device comprising a sample cell for collection of a predetermined volume of sample to be analyzed and means for performing wet chemical analysis on the sample by progressively adding to the sample a measured flow of liquid reagent to cause progressive reaction with sample while sensing a parameter of the liquid sample as the reaction with the reagent proceeds,

• the improvement wherein said chemical analyzer device further comprises
• a siphon cell having a closed volume that serves as said sample cell,
• sample inlet conduit means for delivery of a flow of process liquid into said cell,
• vent means for flow of vent gas into said cell,
• siphon/drain conduit means having an inlet and an outlet, said conduit means having a first end defining said inlet downwardly disposed within the volume of said cell with said inlet at a predetermined level spaced from the bottom and top of said cell, the partial volume of said cell below said inlet sized to define a predetermined volume of sample to be analyzed, and the partial volume of said cell above the level of the inlet enabling additional liquid to be introduced into said cell during the operation of said device, and said siphon/drain conduit means having a second end defining said outlet downwardly disposed outside said cell with said outlet disposed at a predetermined distance below said inlet,
• means for causing flow of process liquid through said sample inlet conduit means into said cell to collect a sample in said cell and establish a level of liquid in said cell above the inlet of said siphon/drain conduit means, and thereafter, by continued flow of liquid into said cell volume via said sample inlet conduit means, to establish flow of excess process liquid out of said cell volume through said siphon/drain conduit means, to cause said siphon/drain conduit means to fill,
• means for ceasing flow through said sample inlet conduit means after said siphon/drain conduit means, is filled and means for creating siphoning flow through said siphon/drain conduit means to drain excess process liquid from said cell in the manner that siphoning flow ceases automatically when the level of process liquid in said cell volume reaches the level of said inlet of said siphon/drain conduit means, thereby to define, in said cell, a sample of predetermined repeatable volume, and
• said means for performing wet chemical analysis constructed to perform said analysis in situ within said siphon cell by titrating techniques, comprising means for progressively delivering into said siphon cell a measured flow of liquid reagent to cause progressive reaction with sample in situ in said cell, and means for sensing in situ in said siphon cell a parameter of the liquid sample as the reaction with the reagent proceeds.