JPH07103867A - Method for supplying sample to moisture measuring equipment - Google Patents

Abstract

PURPOSE:To enhance accuracy in the measurement of moisture by drying the carrier gas using an electrolytically regenerative phosphorus pentoxide dehydrator thereby dehydrating the carrier gas reliably for a long term. CONSTITUTION:Phosphorus pentoxide(P2O5) absorbs water(H2O) to produce metaphosphoric acid(2HPO3) which returns back to phosphorus pentoxide through electrolysis upon application of voltage (2HPO3 H2+1/202+P2O5). When a flow rate of gas in the range of 100-500ml/min is required, two platinum wires and two copper wires having diameter in the range of 0.1-1mm are wound alternately around a copper pipe of 1.2-2.0mm. It is then inserted into a glass pipe and secured to the inner wall thereof by heating and then copper is dissolved into a nitric acid solution thus leaving only platinum. Two platinum wires, spaced apart from each other, are employed as anode 32 and cathode 33 which are fed with P2O2 solution and dried. A voltage of 5-90V is then applied to cause electrolysis for forming a thin film of P2O5 between the electrodes 32, 33 thus providing a regenerative dehydrator. This constitution allows easy removal of moisture from carrier gas for a long term.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moisture measuring method in which moisture in a sample is vaporized by heating, introduced into a measuring container of a moisture measuring device by a carrier gas, and titrated there.
In particular, it relates to a method of supplying a sample to a measurement container.

[0002]

The Karl Fischer titration method is widely used for measuring the water content of various samples. The Karl Fischer titration method uses the following Karl Fischer reaction

[0003]

[Equation 1] SO ₂ + I ₂ + H ₂ O + 3Base + CH ₃ O
H → 2 BaseH ・ I + BaseH ・ SO ₄ CH ₃

This is a titration method utilizing the method, and there are a volumetric analysis method and a coulometric titration method. Then, a Karl Fischer reagent suitable for each method is used for titration. Although a liquid sample having good fluidity can be directly introduced into a titration cell to measure water content, a method of directly introducing it into a titration cell is rarely used for water content measurement of a solid sample or a viscous liquid sample.

This is because the sample is not dissolved in the solvent, so that the extraction of water is not sufficient and the measurement becomes inaccurate. In such cases, depending on the sample, dozens of degrees Celsius to 1000 degrees Celsius
The moisture is vaporized from the sample using a heating vaporizer that holds a heating furnace that can variably heat up to, and is expelled by a carrier gas, and the moisture is introduced into the titration cell for measurement.
Nitrogen gas or air, and sometimes argon gas is usually used as the carrier gas, and the carrier gas contains several tens of ppm (V / V) of water. Therefore, the water content in the sample cannot be distinguished from the water content in the carrier gas, so that the water content in the low concentration range cannot be measured unless the carrier gas is dehydrated.

Conventionally, for the dehydration of carrier gas, commercially available reagents such as phosphorus pentoxide, molecular sieves and silica gel have been used alone or in combination.

[0007]

However, in the conventional desiccant as described above, the time when the dehydration effect disappears is unknown from the appearance, and when the dehydration effect disappears, it is necessary to replace it with a new one. There was a drawback that was. Further, although molecular sieves and silica gel are easy to handle, it is difficult to understand the state of deterioration of water removal capacity, and the water removal capacity is lower than that of phosphorus pentoxide. Further, in the case of the reagent phosphorus pentoxide, it is difficult to handle since it has a high water removal capacity but tends to absorb moisture, and when it is discarded, it reacts violently with water, which is dangerous. As described above, the conventional heating vaporization device has a problem in the method of dehydrating the carrier gas.

[0008]

Means for Solving the Problems As a result of intensive studies to overcome the above-mentioned problems, the present inventors found that the carrier gas was dried sufficiently by using an electrolytic regeneration phosphorus pentoxide dehydrator. It is possible to supply a sample to a moisture measuring container using a carrier gas, and it is possible to remove moisture over a long period of time, which makes it easy to handle,
The present invention has been reached.

That is, the object of the present invention is to provide a sample supply method in a water content measuring device for vaporizing water in a solid or liquid sample by heating and supplying the vaporized water into a measurement container by a carrier gas. Has already passed through the electrolytic regeneration type phosphorus pentoxide dehydrator in advance, which is easily achieved by the sample supply method in the water content measuring device.

The present invention will be described in detail below. Figure 1
It is a schematic diagram of an example of a heating vaporization unit used in the method of the present invention,
FIG. 2 is a schematic diagram showing a moisture measuring method to which the method of the present invention is applied, and FIG. 3 is a schematic diagram of an electrolytic regeneration phosphorus pentoxide dehydrator used in the present invention. In the sample supply method of the present invention, first, moisture in the solid and liquid samples is vaporized by heating.

The vaporization method is not particularly limited,
For example, as shown in FIG.
The sample 13 to be measured enclosed in the heat-resistant heating container 12 is heated as expected to vaporize water. Next, as schematically shown in FIG. 2, using a carrier gas that has been passed through an electrolytic regeneration phosphorus pentoxide dehydrator 21 and sufficiently dried, it is vaporized from a heating vaporization section 22 containing the heating container 12. The water contained in the sample is discharged and introduced into a measurement container provided in the water measuring unit 23. As described above, nitrogen, argon, oxygen or the like is generally used as the carrier gas.

Further, as a method of discharging the vaporized water,
Although not particularly limited, for example, as shown in FIG. 1, a carrier gas is introduced from a carrier gas introducing pipe 14 communicated with the heating container 12 to cause the water inside the heating container 12 to be purged so as to contain the water after the treatment. The carrier gas is discharged from the carrier gas discharge pipe 15.

The discharged carrier gas is introduced into a measuring container (not shown) provided in the moisture measuring section, and the amount of moisture contained in the sample is measured. The principle of the electrolytic regeneration type phosphorus pentoxide dehydrator constituting the present invention is described in US Pat.
A detector having the same principle as the detector of the moisture meter shown in the specification of 0,945 is used. The principle is that phosphorus pentoxide absorbs water to become metaphosphoric acid, but this metaphosphoric acid is electrolyzed at the electrode to which a voltage is applied and returns to the original phosphorus pentoxide.

[0014]

[Equation 2] H ₂ O + P ₂ O ₅ → 2HPO ₃ (1) 2HPO ₃ → H ₂ + 1 / 2O ₂ + P ₂ O ₅ (2)

An example of the manufacturing method of the dehydrator will be described with reference to FIG. Two platinum wires and two copper wires each having a diameter of 0.1 to 1 mm are alternately wound on a copper pipe having an appropriate thickness, for example, 0.5 to 2 mm. The coiled platinum wire or copper wire inserted into a glass tube 31 having a diameter slightly larger than that of the coiled wire is heated on the inner wall of the glass tube 31 to shrink and fix the glass tube 31. After this, the nitric acid solution dissolves copper to leave only platinum. This leaves two platinum wires that do not touch each other alternately, so that the anode 32 and the cathode 3 respectively.
Set to 3. The dehydration pipe may be used in a straight line, and U
You may make it a character shape. Further, after flowing a phosphoric acid solution, it is dried, and a voltage of preferably 5 to 90 V is applied to both electrodes to electrolyze phosphoric acid. By this electrolysis, a thin coating of phosphorus pentoxide is formed between the electrodes, and the electrode can be used as a dehydrator.

The phosphorus pentoxide moisture detector that has been used already has an extremely small inner diameter as described in the above-mentioned manufacturing method, and a quantitative reaction did not occur unless the gas flow rate was 100 ml / min or less. In the heating vaporizer of the present invention, a gas flow rate of 100 to 500 ml / min is usually required. Therefore, the inner diameter of the phosphorus pentoxide dehydration tube is preferably 1.0 to 2.0.
mm. By making it thicker, quantitative dehydration is possible even at a large flow rate. Since a voltage is constantly applied to both electrodes of this dehydration tube, the reactions of the above formulas (1) and (2) are always performed. Therefore, the water removal ability of the dehydration pipe is maintained for a long period of time unless the dehydration pipe is contaminated by foreign matter or the like. If a filter or the like is installed in front of the dehydration pipe in order to prevent dust or the like in the carrier gas from being contaminated, the water removal capability can be maintained for a longer period of time. Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples without departing from the gist thereof.

[0017]

【Example】

Example-1 A dehydrator having a configuration schematically shown in FIG. 3 (outer diameter 3.0 mm,
Inner diameter 1.0 mm, cathode and anode platinum wire diameter 0.2 m
m, length about 1 m) was attached in front of the heating vaporizer to measure water content. For water content measurement, Karl Fischer titrator "CA-06", a micro water content analyzer (Mitsubishi Kasei Co., Ltd.)
Manufactured) was used. About 10 to 30 pp for carrier gas
Nitrogen gas containing m (V / V) of water was used, but using this dehydrator with 30 V applied, half a year has passed (integrated nitrogen gas aeration time of about 1200 hours). There is no deterioration. The background (moisture-converted electrolysis amount per second when water from the sample did not enter) was always 0.03 μg water / sec or less. The background when the dehydrator was removed from this apparatus was 0.23 μg water / sec or more.

Comparative Example-1 A commercially available heating vaporizer "VA-0" using "Shikapent" (manufactured by Merck & Co., Inc.) as a drying agent as a carrier gas dehydrator.
6 "(manufactured by Mitsubishi Kasei Co., Ltd.), the dehydrating effect will be lost and the background will be zero unless the desiccant is replaced once every one month (total nitrogen gas aeration time is about 200 hours). At more than 20 μg water / sec, the dehydration of the carrier gas was insufficient, and accurate water content measurement in the trace amount area was impossible.

[0019]

By using the sample supply method in the water content measuring device of the present invention, it becomes possible to easily remove the water content in the carrier gas for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of a heating vaporization section used in the method of the present invention.

FIG. 2 is a schematic diagram showing a moisture measuring method to which the method of the present invention is applied.

FIG. 3 is a schematic diagram of an electrolytic regeneration type phosphorus pentoxide dehydrator used in the present invention.

[Explanation of symbols]

 Reference Signs List 11 heating coil 12 heat-resistant heating container 13 sample to be measured 14 carrier gas introduction pipe 15 carrier gas discharge pipe 21 electrolytic regeneration type phosphorus pentoxide dehydrator 22 heating vaporization section 23 moisture measurement section 31 glass tube 32 anode 33 cathode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G01N 31/00 Y

Claims (2)

[Claims] 1. A sample supply method in a water content measuring device in which moisture in a solid or liquid sample is vaporized by heating and the vaporized moisture is supplied as carrier gas into a measurement container, wherein the carrier gas is electrolytically regenerated pentoxide. A sample supply method in a moisture measuring apparatus, which is characterized in that the sample is passing through a phosphorus dehydrator. 2. The water according to claim 1, wherein the electrolytic regenerated phosphorus pentoxide dehydrator is composed of a metal electrode and phosphorus pentoxide, and a voltage applied between the electrodes is 5 to 90V. Sample supply method in measuring device.