JP2015179056A - Moisture measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic cathode capable of preventing breakage and being maintained easily when removing foreign matters adhered to a conductive part, because a unilocular electrolytic electrode (S) is a minute electrode, and there are problems for example, in a unilocular electrolytic method applying a Karl Fischer coulometric titration, the unilocular electrolytic electrode (S) is an important superficial area, and has a structure in which a platinum wire having about 0.3 mm of diameter is sealed to a glass which is heated and melted in consideration of chemical resistance, and the conductive part is projected from a glass face by about 0.5-1 mm, but the heated and melted glass face has an irregularity, and it is extremely hard to make projection length of the conductive part uniform.SOLUTION: A surface of a support body 7 of a platinum wire is polished after sealing of the platinum wire 8 for forming a plane, thereby thickness of the platinum wire and a polishing angle can be adjusted for easily setting a superficial area of a unilocular electrolytic electrode (S) 96 to a target value.

Description

  The present invention relates to an electrolytic cathode of a moisture measuring device using Karl Fischer coulometric titration.

Moisture measurement using the Karl Fischer coulometric titration method is widely used in the field of quality control analysis of liquid samples, solid samples, and gas samples because it has the feature of accurately measuring trace moisture (μg order). Has been.
The Karl Fischer coulometric titration method includes a measurement method using a two-chamber electrolysis cell (for example, an electrolysis cell shown in Non-Patent Document 1) or a single-chamber electrolysis cell (for example, Patent Document 1) in the structure of the electrolysis cell. is there. Compared to the method using a two-chamber electrolysis cell (hereinafter abbreviated as two-chamber electrolysis), the measurement method using a one-chamber electrolysis cell (hereinafter abbreviated as “one-chamber electrolysis”) does not use an electrolytic diaphragm. In addition to the fact that no liquid is required and the surface area of the electrolysis cathode can be reduced, the electrolysis cell can be miniaturized, and the manufacturing cost of electrolysis cathode using expensive platinum can be greatly reduced. Yes.

JP 2010-60535 A Japanese Industrial Standard JIS K 2275

Although the importance of the electrolytic cathode and current density of the one-chamber electrolysis method is clarified in Patent Document 1, there is no discussion on maintainability. In order to increase the measurement accuracy, it is necessary to control an electrolysis current on the order of several microamperes, but in order to keep the current density with respect to the electrolysis cathode within a predetermined range, it is necessary to use a very small electrode. In Patent Document 1, a platinum wire having an outer diameter of 0.3 mm and a length of 0.5 mm is proposed as an electrolytic cathode (S) for a minute electrolysis current. At the time of adhesion of cations or viscous samples by electrolysis There was a risk of damaging the electrolytic cathode (S) unless careful care was taken to remove it. In addition, Karl Fischer coulometric titration electrodes are often used by enclosing them in glass tubes in consideration of chemical resistance. However, if the above-mentioned minute platinum wires are encapsulated, they must be manufactured to the specified dimensions. It was difficult. In order to encapsulate platinum wire in glass, the glass is heated to a melting point or higher, inserted there, and cooled to room temperature, so the glass surface around the platinum wire has irregularities and projections of minute platinum wires. This is because it is very difficult to finish the length to a specified dimension in units of 0.1 mm. Further, the unevenness of the glass surface tends to be in a state where hydrogen gas generated on the surface of the one-chamber electrolytic cathode (S) by electrolysis adheres to the platinum wire and the depression of the glass, and as a result, the surface area of the electrolytic cathode (S) is likely to change. (Fig. 3).
An object of the present invention is to solve the above-mentioned problems, improve maintainability, and improve manufacturing yield.

  In order to achieve the above object, the surface of the support of the platinum wire can be achieved by encapsulating the platinum wire and polishing it to make a flat surface (FIG. 2). Further, the surface area of the one-chamber electrolytic cathode (S) can be easily set to a target value by adjusting the thickness of the platinum wire and the polishing angle (FIG. 1).

  According to the single-chamber electrolytic cathode (S) of the present invention, damage during maintenance such as cleaning of electrode deposits can be prevented, and the quality during electrode production can be kept constant, enabling stable moisture analysis. .

The front-end | tip part enlarged view 1 of the one-chamber electrolytic cathode (S) for moisture measuring apparatuses of this invention. The front-end | tip part enlarged view 2 of the one-chamber electrolytic cathode (S) for moisture measuring apparatuses of this invention. A one-chamber electrolytic cathode (S) whose [Effect of the invention] is shown in [Patent Document 1]. The block diagram of the measuring apparatus by the one-chamber electrolysis method which shows one Example of this invention.

  In this example, the structure of the one-chamber electrolytic cathode (S) was polished so that the platinum wire tip sealed in the glass electrolytic cathode support was flush with the electrolytic cathode support (FIG. 1). ) And (FIG. 2) and the conventional one-chamber electrolytic cathode (S) (FIG. 3) were measured as shown below, and it was confirmed that there was no problem in measuring moisture. .

表１の結果より、バックグラウンド値は特許文献１で発明の効果を説明した図３の一室電解陰極（Ｓ）と、図１および図２の一室電解陰極（Ｓ）は同一となり、同じ効果があることが判る。また、図４で示した測定装置で一室電解陰極（Ｓ）
に流す必要がある最大電流値は、バックグラウンド値として１分間に９９マイクログラムの水分に相当する電解電流で、その値はファラデーの法則により１７．７ｍＡで、図１〜図３の一室電解陰極（Ｓ）は全て要件を満たしている。When the diameter of the platinum wire of the conventionally used single-chamber electrolytic cathode (S) shown in FIG. 3 is 0.3 mm and the length L1 is 0.8 mm, the surface area is 1.0 square mm. When the diameter D1 and the polishing angle θ of the platinum wire in FIG. 1 are calculated from the formula of the elliptical area so as to have the same surface area as this one-chamber electrolytic cathode (S), the polishing angle is obtained when D1 is 0.8 mm. θ can be calculated as 60 °. The surface area of the one-chamber electrolytic cathode (S) manufactured to this specification is 1.0 square mm. Moreover, although the diameter D2 of the platinum wire of FIG. 2 is 1.1 mm in diameter according to the formula of the area of the circle, it is manufactured with a practically available 1.2 mm. The surface area of the single-chamber electrolytic cathode (S) manufactured to this specification is 1.1 square mm.
About the manufactured three one-chamber electrolysis cathodes (S), the measurement result shown in FIG. 4 is used, and the measurement result of the background value in the state in which nitrogen gas is vented as in the measurement in Patent Document 1, and the maximum current that can flow. The results of comparing the values are shown in Table 1.

From the results in Table 1, the background value is the same for the one-chamber electrolysis cathode (S) in FIG. 3 and the one-chamber electrolysis cathode (S) in FIG. It turns out that there is an effect. In addition, the measurement device shown in FIG.
The maximum current value that needs to be passed through is an electrolysis current equivalent to 99 micrograms of water per minute as a background value, which is 17.7 mA according to Faraday's law. All cathodes (S) meet the requirements.

1. Drying tube 2, indicator electrode 3, electrolytic cell 4, electrolytic solution 5, magnetic piece 6, electrolytic anode 7, electrolytic cathode support 8, single chamber electrolytic cathode (L)
9. One-chamber electrolytic cathode (S)
9a, conventional single-chamber electrolytic cathode (S)
9b, improved one-chamber electrolytic cathode (S)
9c, improved one-chamber electrolytic cathode (S)
10, input amplifier 11, microcomputer 12, electrolytic power supply 13, display 14, keyboard 15, printers 16 and 17, lead wires

Claims (2)

An electrolytic cell for containing an electrolytic solution, an electrolytic anode provided in the electrolytic cell for electrolyzing the electrolytic solution, a single-chamber electrolytic cathode (L), a single-chamber electrolytic cathode (S), and a state of the electrolytic solution In a moisture measuring apparatus comprising an indicator electrode and a microcomputer for controlling electrolysis according to a signal from the indicator electrode, the conductive portion of the one-chamber electrolytic cathode (S) and the surface of the conductive portion support are polished. A moisture measuring device provided with a one-chamber electrolytic cathode (S). A single-chamber electrolytic cathode (S) characterized in that the polishing surface of the single-chamber electrolytic cathode (S) of the moisture measuring device is polished at an angle of 0 to 85 degrees with respect to the conductive portion and the conductive portion support. Moisture measuring device.

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