JPH0311733Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a reference electrode used for measuring pH and various ion concentrations.

Recently, pure water has been widely used in various industries, and the PH
Values are determined and controlled. Also, 0.1μs/
It has become possible to produce highly purified water on the order of cm, and it is now required to be able to stably measure its PH value.

PH measurement of pure water with extremely low ion concentration uses various PH methods.
It is one of the most difficult measurements. This is because, in addition to the non-relaxation nature of the liquid itself, the liquid junction of the reference electrode comes into contact with the low ion concentration liquid, resulting in a difference in potential between liquids and a flowing potential, causing fluctuations in measured values and errors.

In order to prevent this, the liquid junction may be always covered with a liquid having a high ion concentration (for example, a potassium chloride solution) so that a solution having a low ion concentration does not come into direct contact with the liquid junction.

For this purpose, as shown in FIG. 1, a depression 6 is provided in the measurement chamber 5 in which the measurement electrode (glass electrode) 1, the comparison electrode 2 and the temperature compensation electrode 3 are installed, and the liquid junction part 8 of the comparison electrode 2 is placed in the depression 6. so that the liquid junction 8 is always in the stationary liquid, and the internal liquid (saturated potassium chloride solution) flowing out from the liquid junction 8 becomes a solution with high ion concentration near the liquid junction 8. The liquid to be measured 4 is being measured. However, in recent years, as ultrapure water of 0.1μs/cm or less has been used, slight changes in flow rate can cause the liquid junction to
Even if the stationary liquid near is slightly disturbed, the measured value will become unstable.

In addition, as shown in FIG. 2, if the liquid junction part 8 is placed inside the cover 7 having an opening 7a at the bottom so as to be as little affected as possible by changes in flow rate, the gap between the measuring electrode 1 and the reference electrode 2 can be Disadvantages occurred in that the distance was long and the solution resistance between the measurement electrode 1 and the comparison electrode 2 increased due to the low ion concentration solution, increasing the impedance of the measurement system and making it susceptible to external induction.

FIG. 3 is a cross-sectional view of a double junction type reference electrode used in the conventional PH measurement of pure water. A liquid junction part 8 consisting of a porous substance 8a that adjusts the outflow amount of the internal liquid 10 to a constant level and a hollow plug 8b that holds this is attached to the support tube 9, and the internal liquid (saturated chloride) flowing out from the porous substance 8a is attached to the support tube 9. The structure is such that the potassium solution (10) directly contacts the liquid to be measured. For this reason, the ion concentration near the porous material 8a is disturbed by the flow of the liquid to be measured, resulting in a drawback that the measured value becomes unstable. An inner electrode (silver-silver chloride electrode) 11 is immersed in the internal liquid 10 to generate a certain amount of superpower. 12 is a supply port for the internal liquid 10;
3 is a cap, and 14 is a lead wire.

The present invention was devised to eliminate the above-mentioned drawbacks inherent in the conventional technology. Therefore, the purpose of the present invention is to ensure that the liquid junction is always in contact with a solution with a high ion concentration, and that there is little influence from changes in flow rate. The object of the present invention is to provide a novel comparison electrode that can obtain a stable liquid junction potential difference without increasing the impedance of the measurement system.

The above object of the present invention is to provide a reference electrode used for measuring pH or various ion concentrations, in which the liquid junction is composed of a porous material that regulates the flow rate of the internal liquid to a constant level, and a continuous electrode that is hydrophilic and has a water retention capacity. This is achieved by a reference electrode which is composed of a spongy material with pores and is characterized in that the porous material and then the spongy material are arranged in this order in the direction in which the internal liquid flows out.

Next, preferred embodiments of the present invention will be explained in detail with reference to the drawings.

FIG. 4 is a sectional view of essential parts showing an embodiment of the present invention. In the figures, the same reference numbers as in Figure 3 refer to
Shows the same elements as in the figure. Liquid junction 8 is internal liquid 1
A porous material 8a that adjusts the outflow amount of water to a constant level, and a spongy material 8 with continuous pores that is hydrophilic and has a water retention capacity.
c and a support tube 9 and a removable plug 8b.

For example, porous ceramic or specially processed tetrafluoride resin is used as the porous material 8a.
Spongy material 8c with continuous pores has a porosity of 70 to 90%.
PVF (polyvinyl formal) resin is used, but other foams, sponges, or cotton may also be used as long as they are hydrophilic, open-pore, and spongy materials with water-holding capacity. For example, a hollow tapered elastic body is used for the plug 8b.
In the other embodiment of the figures, a hollow plastic with a tapered external thread on the side, indicated by reference numeral 8d, is likewise used, which is connected in a gas-tight manner to the support tube 9 and is also of removable construction.

The bonding state between the porous material 8a and the spongy material 8c is as follows.

Porous material 8a in the direction of outflow of the internal liquid;
be arranged in the order of spongy material 8c;

The porous material 8a and the spongy material 8c only need to be in physical contact with each other, and do not need to be integrated by adhesive or other means.

During manufacturing, the porous material 8a is press-fitted from the end surface of the plug 8b (or 8d) in contact with the support tube 9 in FIGS. 4 and 5, and then the spongy material 8c is press-fitted from the opposite end surface, Next, a spongy substance 8c is press-fitted from the opposite end face.

The internal liquid flows out from the porous 8a due to gravity,
It soaks into the spongy substance 8c. Moreover, since the spongy substance 8c absorbs the test liquid when it comes into contact with it, a gradual concentration gradient of the potassium chloride solution occurs inside the spongy substance 8c.

By configuring as described above, the internal liquid (saturated potassium chloride solution) 10 flowing out from the porous material 8a is mixed in contact with the low ionic concentration solution inside the spongy material 8c having continuous pores, resulting in a gradual concentration. The high concentration internal solution does not come into direct contact with the low ion concentration solution.

As explained above, according to the present invention, since the liquid junction is always in contact with the high ion concentration solution,
A stable liquid junction potential difference can be maintained, and since the liquid junction itself has a structure with a cover that is open at the bottom, it is less susceptible to changes in flow rate, and the impedance of the measurement system does not increase.
It has the advantage of being resistant to external guidance.

Although the present invention has been described above with respect to its preferred embodiments, these are merely illustrative, and the present invention is not limited only by the embodiments described herein, and does not depart from its scope. It is easy to make various modifications and changes without any trouble. for example,
This reference electrode can be used not only to measure the pH of pure water, but also to measure the ORP (oxidation-reduction potential) of pure water and the concentration of various ions in pure water. Naturally, it can also be used to measure things other than pure water, in which case it is less susceptible to the influence of dynamic pressure due to flow velocity (generation of streaming potential), and also has the effect of acting as a filter to prevent clogging of porous materials due to dirt. . Furthermore, as shown in Figures 4 and 5, it goes without saying that the porous material and spongy material can be attached directly to the support tube without using a plug to hold the porous material and spongy material. do not have.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the structure of a measurement chamber, Figure 2 is a sectional view showing the structure of a measurement chamber with a cover attached to the liquid junction, and Figure 3 is a cross-sectional view of a conventional double junction type reference electrode. 4 is a cross-sectional view of the liquid junction portion showing one embodiment of the reference electrode according to the present invention; FIG. 5 is a cross-sectional view of the liquid junction portion showing another embodiment of the present invention. . DESCRIPTION OF SYMBOLS 1... Measuring electrode, 2... Comparison electrode, 3... Temperature compensation electrode, 4... Liquid to be measured, 5... Measuring chamber, 6... Recess, 7... Cover, 7a... Opening, 8, 8'...liquid junction, 8a...porous material,
8b... Hollow plug, 8c... Spongy substance, 9
... Support tube, 10 ... Internal liquid, 11 ... Inner pole, 1
2... Supply port, 13... Cap, 14... Lead wire.

Claims (1)

[Scope of utility model registration request] In reference electrodes used for pH or various ion concentration measurements, the liquid junction is made of a porous material that regulates the outflow of internal liquid to a constant level, and a spongy material with continuous pores that is hydrophilic and has a water-retaining ability. 1. A comparison electrode, characterized in that the porous material and then the spongy material are arranged in this order in the direction in which the internal liquid flows out.