JPH03295460A - Rotary electrode and concentration measuring method - Google Patents

Abstract

PURPOSE:To easily measure the concentration of a material to be electrolyzed with high accuracy by providing a pair of a cathode and an anode to a rotary terminal in parallel at an interval of <=1mm and connecting them to a power source and a measurement part. CONSTITUTION:The pair of the cathode 1 and anode 2 which are provided in parallel at the interval of <=1mm are fixed to the rotary terminal and only their tip parts are exposed. Further, the electrode consists of an insulation part 3A which is insulated from other constitution parts, a current collection brush 5 which connects the cathode 1 and anode 2 to the power source and measurement part, and an electric feeding ring 4. When the interval between the electrodes 1 and 2 is set to <=1mm, the measurement accuracy is improved. When the interval is set to 0.5 - 0.3mm, the influence of dust, etc., in the sample is eliminated and noise generation is prevented. Then the concentration of the material to be measured in a slurry, a high-viscosity solution, a colloid solution, etc., which are hardly obtained in a uniform diffusion tank can continuously be measured with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a rotating electrode and a concentration measuring method, and more specifically to measuring the concentration of an electrolyte contained in a slurry, colloidal solution, high viscosity solution, etc. This invention relates to a suitable rotating electrode and a concentration measurement method using the same.

[Prior Art] A rotating electrode is one in which the electrode is connected to a rotation drive device and rotated in a liquid to be measured to generate an electrolytic current in the liquid to be measured between a working electrode and a counter electrode. The method of measuring solute concentration in a solution using a rotating electrode equalizes the thickness of the diffusion layer of the analyte in the solution and obtains a stable electrolytic current (limiting diffusion current) proportional to the concentration of the analyte. Therefore, it occupies an important position in electrochemical analysis.

As this rotating electrode, a rotating wire electrode, a rotating disk electrode, a rotating ring/disk electrode, etc. are known.

FIG. 6 is an explanatory diagram of a conventional quantitative method using a rotating electrode, which requires a fixed electrode 21 as a counter electrode in addition to a rotating electrode 20 with either a cathode or an anode as a single pole (working electrode). be. For example, as shown in FIG. 6A, a rotating ring-disk electrode has a disk pole 24 at the center of a rotating pole 20 and a ring pole 23 concentrically therewith as a working pole.
The electrolytic solution 22 flows from the disk electrode to the outer ring electrode by the rotation of the disk electrode 24, and the electrochemically active substance electrolytically produced at the disk electrode 24 is captured and detected by the ring electrode 23.

In addition, ultra-fine electrodes such as micro-comb electrodes are used as electrodes that can diffuse the electrolyte in a nearly three-dimensional state without rotating the electrode or moving the solution7 to obtain a steady diffusion current. Are known.

However, with the above-mentioned rotating electrodes and ultra-microelectrodes, it is necessary to obtain a uniform diffusion layer of the measured @lj quality, which limits the measurement of samples in which a diffusion layer is easy to obtain. There has been a problem in that the concentration of a substance to be measured contained in a viscous solution, colloidal solution, etc. cannot be accurately measured.

[Problems to be Solved by the Invention] An object of the present invention is to solve the problems of the prior art described above, and to measure the concentration of an electrolyte contained in slurry, high viscosity solution, colloidal solution, etc. with high precision using a simple device. An object of the present invention is to provide a rotating electrode capable of measuring concentration and a concentration measuring method using the same.

[Means for Solving the Problems] The present invention is characterized in that at least one pair of cathodes and anodes connected to a power source and a measuring section, respectively, are provided on a rotating terminal in parallel with an interval of 11 or less. The present invention relates to a rotating electrode, and a concentration measuring method in which the rotating electrode is immersed in or in contact with a sample and rotated to measure the concentration of an electrolyte in the sample.

[Function] By arranging the cathode and anode parallel to each other at a spacing of less than 1 meter on the rotating terminal, it is possible to spread the light in the sample without installing a fixed pole in the sample, and without being limited to samples where it is easy to obtain a diffusion layer. The concentration of the electrolyte can be measured with high accuracy.

FIG. 1 is a perspective view of a rotating electrode showing an example of the present invention. In the figure, the rotating electrode 3 includes a pair of cathode 1 and anode 2 that are arranged in parallel with an interval of one threshold or less, and the cathode 1 and anode 2 are fixed, with only their tips exposed, and the other The current collecting brush 5 and the power feeding ring 4 connect the cathode 1 and the anode 2 to a power source and a measuring section, respectively. Precious metals such as platinum are used as the material constituting the cathode 1 and the anode 2, and copper, SUS, etc. can also be used for the cathode.

The exposed position of the cathode 1 and the anode 2 may be at the bottom of the rotating electrode 3 or at the side as shown in FIG. 1A. Also, the insulation part 3
For A, resins such as epoxy resin, vinyl chloride resin, and phenol resin, ceramics, and the like can be used.

The above-mentioned cathode 1 and anode 2 are selected from III[1] in terms of measurement accuracy.
It is necessary to provide them in parallel with an interval of 1 or less. The narrower the spacing between the electrodes, the better the measurement accuracy, but it is less susceptible to the effects of dust in the sample and the noise generation rate increases.
It is preferably about 75 mm to 0.1 mm, more preferably about 0.5 mm to 0.3 mm. For homogeneous samples with few contaminants, it is possible to perform more accurate measurements by using electrodes with narrower spacing. Although at least one pair of cathode and anode is sufficient, the cathode and anode may be arranged alternately and used as a comb-shaped electrode (see FIG. 1B). The greater the number of electrodes, the higher the measurement accuracy, but if there are too many, some of the electrodes may protrude from the sample.
Requires a viewing window for handling. Further, the length of the electrode is preferably short from the viewpoint of measurement accuracy, and is preferably 20 plates to 10 mm or less, and more preferably about 5 plates.

FIG. 2 is a diagram showing an example of a concentration measuring device using a rotating electrode of the present invention.

In the figure, a synchronous motor 9 is placed on the lower part of the pedestal 12, and a support 8 is provided below the pedestal 13 via a spring 14, and a container containing a sample 6 is placed on the pedestal 8. 7 is placed on the container 7, and the rotating electrode 3 installed on the rotating shaft of the motor 9 is inserted into the sample 6 in the container 7.

After the sample 6 is placed in the container 7 on the support stand 8, the electrode 1.2 of the rotating electrode 3 is immersed in or in contact with the sample, and the rotating electrode 3 is rotated by the synchronous motor 9. The rotation speed is usually 100 to 3000 rpm. A power supply ring 4 provided above the rotating electrode 3 contacts a current collecting brush 5 connected to a constant voltage power source 10 and a recorder 11, respectively, to supply voltage to the electrode 1.2. By applying a voltage, electrode 1.
The electrolytic current generated in step 2 is input to the recorder 114 via the power supply ring 4 and the current collector brush 5, and from this electrolytic current value, the concentration of the electrolyte is calculated based on the calibration curve input in advance to the recorder 6. be done. During calculation, it is preferable to perform temperature correction in order to eliminate the influence of temperature and improve measurement accuracy.

The electrolytic current can also be measured continuously by immersing the rotating electrode 3 in a sample moving at a relatively constant speed, for example on a heald conveyor. In this case, since a sample moving at a constant speed is measured, there is almost no precipitation of metals or metal hydroxides at the cathode, which does not interfere with continuous measurement.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1.2 and Comparative Example 1.2 The water content of dehydrated sludge was adjusted to four levels, and the water content in this dehydrated sludge was measured using the apparatus shown in FIG. 2 using the rotating electrodes shown in FIGS. 1 and 1A. Quantitative properties were examined by comparing these values with those measured by dry weighing. A platinum plate electrode with a thickness of 0.5 mm and a length of 5 mm was used as the rotating electrode, and the electrode was rotated at a rotation speed of 600 rpm, and a voltage of 4 mm was applied at room temperature. The results are shown in FIG. 3, and it was found that good quantitative properties were exhibited.

Further, as Comparative Examples 1 and 2, the water content of dehydrated sludge was measured in the same manner as above using a conventional rotating disk electrode and a rotating wire electrode, but no quantitative results were observed.

Example 3.4 Vitamin C (reduced form!-ascorbic acid) was added to starch slurry, and the concentration of vitamin C was measured using the apparatus shown in FIG. 2 using the rotating electrodes shown in FIGS. 1 and 1B, respectively. We examined its quantitative nature.

The same electrode as in Example 1 was used as the rotating electrode in FIG.
The comb-shaped electrode in Figure 1B is 3III11×3ffI
A comb-shaped electrode was used in which four rows of cathodes and three rows of anodes were alternately arranged in an area of I11. Further, it was rotated at a rotational speed of 120 rpm, and a voltage of 2 μ was applied at room temperature. The results are shown in FIG. 4, and it was found that good quantitative properties were exhibited.

Example 5 The electrolytic current when 100μβ of water was added to isopropanol 100Id was measured using the rotating electrode shown in Fig. 1.
Continuous measurements were taken using the equipment shown in the figure. The results are shown in FIG. 5, and it was found that an electrolytic current proportional to the water content could be obtained.

Example 6.7 The rotating electrodes shown in Fig. 1 were prepared with platinum plate electrode lengths of 7 mm and 5 mm, and the water content in the dehydrated sludge on the heald conveyor was determined at a rotation speed of 6.0 Orpm and an applied voltage of 4. Measured continuously. The measurement accuracy at this time is 0.5 to 2% for the 7-electrode and 0.0 to 1.0 for the 5M electrode.
% range.

The measurement accuracy was calculated as follows.

〔Effect of the invention〕

According to the rotating electrode of the present invention, the concentration of the substance to be measured contained in slurry, highly viscous solution, colloidal solution, etc. in which it is difficult to obtain a uniform diffusion tank, such as the water content in dehydrated sludge, can be continuously increased using a simple device. Can be measured with precision.

[Brief explanation of drawings]

1, 1A, and 1B are perspective views of a rotating electrode showing an example of the present invention, FIG. 2 is a diagram showing an example of a concentration measuring device using the rotating electrode of the present invention, and FIG. Figure 4 shows the relationship between the water content in dehydrated sludge and electrolytic current measured using the rotating electrode of the present invention, and Figure 4 shows the relationship between the vitamin C content and electrolytic current measured using the rotating electrode of the present invention. Figure 5 is a diagram showing the relationship between the water content in isopropanol and the electrolytic current measured using the rotating electrode of the present invention, and Figure 6 is a diagram showing the relationship between the electrolytic current and the water content in isopropanol measured using the rotating electrode of the present invention. Illustration, No. 6A
The figure shows the structure of a rotating ring-disk electrode. 1... Cathode, 2... Anode, 3... Rotating electrode, 3A
... Insulation section, 4 ... Power supply ring, 5 ... Current collection brush, 6 ... Sample, 7 ... Container, 8 ... Support stand, 9 ... Synchronous motor , 10... Constant voltage power supply, 11... Recorder, 20... Rotating pole, 21...
Fixed electrode, 22... Electrolyte, 23... Ring electrode, 24
...Disc pole.

Claims (2)

[Claims] (1) A rotating electrode characterized in that at least one pair of a cathode and an anode, each connected to a power source and a measuring section, are provided on a rotating terminal in parallel with an interval of 1 mm or less. (2) A concentration measuring method in which the rotating electrode according to claim (1) is immersed in or in contact with a sample and rotated to measure the concentration of an electrolyte in the sample.