RU1827617C - Device for coulometric titration of liquids by electrically generated iodine - Google Patents

Abstract

Usage: biochemistry, forensics, industrial hygiene, analytical chemistry. The inventive device is made in the form of a glass, the bottom of which is an indicator glass-carbon electrode, the peripheral part of which is coated with a film of a chemically resistant dielectric. The diameter of the working part of the electrode is not more than the diameter of the glass. The wall of the glass is a fluoroplastic cylinder with an annular groove at the bottom, along the perimeter of which the other three electrodes are located above. The glass stopper has an opening for introducing a microsyringe needle directly into the solution layer. The surface of the turntable of the magnetic stirrer is roughened, and its size does not exceed the diameter of the working part of the electrode. Detection limit 2 three. 2 ill. mole of thiosulfate per

Description

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The invention relates to instrumental methods of analysis and may find application in the chemical industry, industrial hygiene, biochemistry and other industries.

The object of the invention is to increase the sensitivity of measurements.

Figure 1 shows the described device, figure 2 is a section aa in figure 1.

The device is made in the form of a cup, the bottom of which is a flat carbon-carbon disk that serves as the main indicator electrode 1, and the wall is a fluoroplastic cylinder 2 with platinum generator 3, 4 and auxiliary indicator 5 electrodes mounted in it. The body and bottom are secured with screws 6. On top, the glass is closed with a fluoroplastic stopper 7 with an opening; 8 - pinwheel of a magnetic stirrer; 9-working solution; 10

- an insulating film of a chemically resistant dielectric.

The main indicator electrode 1 is a glass-carbon disk with a diameter of 40 mm. A film of phenol-formaldehyde polymerized resin with a thickness of 20-30 μm is deposited on its periphery in the form of a ring with an inner diameter of 14 mm. Pieces of platinum wire 100 μm with a visible surface of 2 mm2 were used as generator 3.4 and indicator 5 electrodes. The outer diameter of the housing is 40 mm, the inner diameter is 15 mm. In the lower part of it is made an annular protrusion, providing better sealing. The pinwheel is made in the form of a steel wire enclosed in an 8 polyethylene ampoule with an outer diameter of 0.6 mm and a length of 13.5 mm.

The device operates as follows.

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A solution of potassium iodide is poured into the cell, closed with a stopper 7 and the stirrer is turned on. At the same time, the generator electrodes are connected to an electronic galvanostat, and the indicator electrodes are connected to a recording nanoammeter, and a polarizing voltage is applied to the electrodes. A blank experiment is carried out, for which, simultaneously with the registration of the indicator current, the generator current source is switched on, a constant current of a predetermined value is passed through the generator electrodes, and the time interval until the current appears in the indicator circuit is recorded. The generation current is turned off, and after the indicator current is established in time with a chromatographic syringe, a portion of the analyzed solution is introduced. The titration operation is carried out similarly. The duration of the titration is determined by the distance on the chart tape traversed by the pen of the recorder from the moment of input to the appearance of the indicator signal. Having thus determined the amount of electricity, go

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According to the Farada law, the mass of the analyte is found for titration with allowance for the blank experiment. Detection Threshold 2 10 mol.

Claims (1)

SUMMARY OF THE INVENTION A device for coulometric titration of liquids with electro-generated iodine, including a housing made in the form of a fluoroplastic cylinder, the bottom of which is made of glassy carbon and is connected by a current supply and provided with a perimeter with an annular groove, and a generator and auxiliary electrodes, a plug with a hole for inputting samples, are placed in the wall magnetic stirrer, characterized in that, in order to increase the sensitivity, the peripheral part of the glass carbon electrode indicator is coated with a film chemically stable dielectric, while the diameter of the working part of the electrode is not more than the diameter of the glass, and the size of the turntable of the magnetic stirrer does not exceed the diameter of the working part.