Abstract: A shelf-stable, pre-measured reagent for a chlorine determination test. The reagent includes at least a source of iodide and a pH buffer packaged into a tablet. The tablet is packaged in a plastic-lined metal foil envelope that completely surrounds the tablet, to inhibit air infiltration into the package.

Abstract: Apparatus for calibrating an ion analyzer comprises a calibration cell having defined therein a first volume for measuring an ion concentration of a sample when the instrument is operated in a monitoring and a second volume for measuring the ion concentration when the instrument is operated in a calibration mode. The first volume is included in, and forms part of, the second volume so that the matrix for the calibration measurement is essentially identical to that for the sample measurement. A double known-addition is used during the calibration mode to determine the calibration parameters.

Abstract: An improved flow independent method for electrochemical monitoring of a sample stream for the total concentration of a series of ionic species of the form X.sup.-n, H.sub.m X.sup.-n+m where n varies from 1 to m and X.sup.-n is an anion selected from the group consisting of fluoride ion, F.sup.-, and sulfide ion S.sup.-2. The pH of the sample stream is adjusted to a value below the pk.sub.a of the neutral most protonated species of the series. A first electrode sensitive to the activity of X.sup.-n is placed in the adjusted stream. The electric potential developed thereby is measured. A second electrode sensitive to the activity of hydrogen ion H.sup.+ is also placed in the adjusted stream. The electric potential developed thereby is also measured. The potential difference between the first and second electrode is a measure of the total concentration of the series X.sup.-n, H.sub.m X.sup.-n+m.

Abstract: In a potentiometric system for measuring low levels of ion activity, a method of adjusting the pH in a sample stream by the passive addition of low molecular weight acid or base reagent, without dilution of the sample stream, and without introduction of any interfering, reactive or test ions into the sample stream. A membrane is provided, permeable to the acid or base reagent used to adjust sample stream pH, and impermeable to ionic species. The membrane is placed between a reagent reservoir and the sample stream. Constant flow of the sample stream by the membrane maintains the reagent partial pressure differential between the reservoir and the stream, causing diffusion of reagent through the membrane into said stream.

Abstract: In a potentiometric system for measuring low levels of ion activity, a method of adjusting the pH in a sample stream by the passive addition of low molecular weight acid or base reagent, without dilution of the sample stream, and without introduction of any interfering, reactive or test ions into the sample stream. A membrane is provided, permeable to the acid or base reagent used to adjust sample stream pH, and impermeable to ionic species. The membrane is placed between a reagent reservoir and the sample stream. Constant flow of the sample stream by the membrane maintains the reagent partial pressure differential between the reservoir and the stream, causing diffusion of reagent through the membrane into said stream.

Abstract: A method of monitoring the total residual chlorine in solution. A sample stream is extracted from the solution and mixed with a reagent stream containing a dissociated complex of alkali metal ion and iodide ion, and an excess amount of iodide ion. Iodide ion reacts with all the residual chlorine in the sample stream and is converted to iodine. The activity of iodine is then measured in the resultant mixed stream with a first and second electrochemical potentiometric electrode, the first electrode having a noble metal oxidation-reduction element, and the second having an iodide sensitive membrane element. The total residual chlorine is determined from the activity of the iodine.