Abstract: The invention provides a single colorimetric reagent for the measurement of oxidizing agents such as free chlorine in a liquid sample which contains a food dye, whereby the oxidizing agent undergoes a reaction with said food dye. A preferred food dye is Brilliant Blue FCF. There is also provided a control system for regulating the volume of reagent added to a fixed volume of sample according to a control algorithm to give a chosen excess of a reagent compound beyond that required to stoichiometrically react with the target analyte in the sample. Also disclosed are single reagents for colorimetric determination of total alkalinity and calcium hardness.

Abstract: A chemical analyzer analyzes a sample for a target chemical. The sample and reagent are added to a measurement cell until a detectable change is observed. A reference compound, which does not take part in the reaction between the target chemical and reagent, is added to the reagent. By measuring the concentration of the reference compound, the amount of reagent used may be determined. In one embodiment, a mechanism introduces the sample, adds reagent, mixes, cleans, and flushes the measurement cell, which incorporates a longitudinal chamber having inlets for the sample and reagent and an outlet for measured sample/reagent mixtures. A detector located in or adjacent to the chamber between the inlets and outlet and a piston movable in the chamber carries seals such that movement of a piston sequentially opens the inlets and expels the fluid. The analyzer also includes a device that delivers reagent to a measurement cell.

Abstract: The invention provides a single colorimetric reagent for the measurement of oxidising agents such as free chlorine in a liquid sample which contains a food dye, whereby the oxidising agent undergoes a reaction with said food dye. A preferred food dye is Brilliant Blue FCF. There is also provided a control system for regulating the volume of reagent added to a fixed volume of sample according to a control algorithm to give a chosen excess of a reagent compound beyond that required to stoichiometrically react with the target analyte in the sample. Also disclosed are single reagents for colorimetric determination of total alkalinity and calcium hardness.

Abstract: A liquid sample is analysed for a target chemical. A sample solution is added to a measurement cell of known volume and a reagent is incrementally added to the cell until a detectable change is observed. A reference compound, of a known concentration, that does not take part in the reaction between the target chemical and reagent, is added to the reagent and by measuring the concentration of the reference compound the amount of reagent used may be determined. A single mechanism introduces a sample, adds reagent mixes cleans and flushes the measurement cell which incorporates a longitudinal chamber having a number of fluid inlets for sample and reagent and an outlet for measured sample/reagent mixtures, a detector being located in or adjacent to said chamber between the inlets and said outlet and a piston movable in said chamber carrying a series of seals such that movement of the piston sequentially opens the inlets and expels the fluid.