SU947026A1 - Method for potentiometrically detecting chloride ions in water - Google Patents

Description

 one

The invention relates to the determination of the physicochemical properties of substances in an aqueous medium and can be used in various industries to control the quality of desalinated water by chloride ion.

, as a near-electrode solution of a membrane indicator electrode, OD was used. NaCE l solution. The disadvantage of the method is the low sensitivity of the membrane ion-selective electrode (AtjCP, Acgij S), therefore the concentration of chloride ions can not be determined with the use of an EM-C1-01 membrane electrode, commercially available. 20 more than 3.5 pCB. The purpose of the invention is to increase the sensitivity and expansion of the range of measurement of the membrane chlor-selective elect. A potentiometric method for the determination of chlorides in natural waters is known, in which the concentration element is used:

Aqjm

Hdc

AY: KNOj

Hac.kce of the genus (AcjCE,) in the region of small values of chloride ion concentration (up to 35.5 µg / kg). This goal is achieved by introducing ethyl alcohol (hydrolytic, distilled or edible) in an amount of 20-30 ml / kg into the analyzed and calibration solutions, and dilute 0, OO1 N solution is used as the pre-ectrod membrane membrane indicator electrode solution. sodium chloride with the addition of ethyl alcohol in an amount of 2-30 ml / kg, comparative measurements

The indicator electrode was held at a temperature of 12–14 ° relative to a silver-chloride reference electrode in a saturated solution of potassium chloride.

In addition to the main electrolytic key, in order to increase the stability of the measurements, a constant pressure and flow of a 1O% sodium soda solution are used to prevent the diffusion of chloride ions from the reference electrode.

A decrease in the concentration of sodium chloride in the near-electrode solution reduces the diffusion potential at the boundaries of the near-electrode solution — the membrane and membrane — the analyzed solution, and the introduction of the background electrolyte in the near-electrode and measured solutions in the form of ethyl alcohol indicated suppresses the solubility of silver chloride from the chlorine-silver electrode. (, AoS) and electrode half cell (A AcjCE). As a result, the change in the potential of the indicator electrode (sensitivity) increases with variations in the microconcentration of the chloride ions in the measured solution.

The introduction of the background electrolyte into the measured and near-electrode solutions in the form of ethanol suppresses the solubility of silver chloride from the chlorine-silver electrode membrane (AtjCP, Aqf-S), reducing the concentration of sodium chloride in the electrode solution by 1OO times reduces the diffusion potential during measurements in the region low concentrations of chloride ions. The use of a 10% sodium nitrate solution in an intermediate electrolytic key reduces the ingress of chloride ions with sodium nitrate. As a result, the change in the potential of the indicator electrode (sensitivity) increases when the microconcentrations of chloride ions in the measured solution fluctuate. At 12-14 ° C, the inertia of the chlorine selective membrane electrode remains sufficient for practical use and does not exceed 3 minutes.

Example. The determination of the concentration of chloride ions in demineralized water is carried out by direct potentiometric method in which the concentration element is used:

After calibrating the ZM-C1-O electrode using standard solutions of sodium chloride in bleach-free water with ethanol added to standard rabbi & up to O.OOl n NaCE and electrolytic solutions, direct potentiometric measurements of the concentration of chloride ions in the analyzed solution are carried out. To do this, ethyl alcohol is added to it and comparative measurements of the potential of the indicator membrane electrode are carried out at 12-14 6 relative to the silver chloride electrode in a saturated solution of potassium chloride.

In order to increase the stability of the measurements, an intermediate electrolytic key is used in addition to the baseline, in which a constant pressure and flow of 10% sodium nitrate solution is created, which prevents the diffusion of chloride ions from the reference electrode.

As a recording device, a KSP-2 type instrument with a scale of 2O mV, complete with a P-2O1 high-impedance transducer, or a pH meter of pH-262 type with a scale of 25 mV, is used. The measurement error of five EM-C1-O1 electrodes in the concentration range up to 6.0 pCP units does not exceed 0,022 mg / kg.

Thus, the proposed method increases the sensitivity of the membrane ion-selective electrode (AqCP,) and broadens the range. measurements in the region of small values of chloride ion concentrations (up to 35.5 µg / kg). It can be widely used in various industries and for monitoring the quality of desalted water by chloride ion.

Instructions have been developed for direct potentiometric determination of chloride ions. And the validity of the proposed method on standard solutions and desalted 2O production was confirmed.

In tab. 2 - dependence of measurement error in the proposed method on

35.5

15 Regarding the choice of the composition of the near-electrode solution, it should be avenged that the amount of alcohol in the latter, in order to avoid creating additional diffusion potential due to concentration differences, is set the same for the analyzed solution and the calibration solution, therefore, no justification or evidence is required. With regard to the use of dilute solutions of sodium chloride (0, OO1 n.) In the near electrode solution of the indicator electrode, in contrast to the use in the prototype of a more concentrated solution of sodium chloride (OD n.), It should be noted that this difference leads to a decrease in measurement errors when achieved in the proposed method of sensitivity. Thus, the experimental data presented show that we propose the 1st method of potentiometric measurement of chloride ions in water in comparison with the prototype, it possesses a higher sensitivity and sufficient reproduction.

waters of various types for the concentration range {G. to pcr 6.0 units.

In tab. 1 shows the dependence of the sensitivity of the method on the concentration of alcohol introduced into the analyzed and calibration solutions at different temperatures.

Table 1

the concentration of sodium chloride in the pre-electrode solution of the indicator electrode.

Claims (1)

Table2 35.5-355 OO270 0, O357 O, O-102 4.O2 2.08x -0.0304 4.82 "G.8b S.bv 3.2x xl6-1x1O- x10-2x10-chO-5 by readability and can be used in determining microgram concentrations of chloride ions, for example, in demineralized water, demineralized condensate, and water-cooled nuclear installations, nuclear and nuclear power plants, as well as in other areas of science and technology where such determinations are required. The invention of the method of potentiometric determination of chloride ions in water, based on direct measurement of the dependence of the potential of the indicator electrode on the concentration of chloride ions using chloride as a electrode solution, characterized in that, in order to increase the sensitivity of the chlorine selective membrane electrode (, and the measured chloride ion concentration (up to 35.5 µg / kg), in 79470 analyzed in calibration solutions are introduced ethyl alcohol in the amount of 2OJO MP / kg, and as An electrode solution of the membrane indicator electro is used for O, OO1, a solution of sodium chloride with the addition of ethyl alcohol in the amount of ml / kg, and the measurement of the potential of the indicator electrode is carried out at 12-14 ° C. 268 Information sources taken into account during the examination I. Zainalov E .A. And Sen WinMM Application of ion-selective electrodes for the determination of (} p-eridus, chlorides and iodides in natural waters. - ЖАХ, 1975 т. 30, № 11 p. 2207-2212