JPH0420139B2 - - Google Patents
Info
- Publication number
- JPH0420139B2 JPH0420139B2 JP10250684A JP10250684A JPH0420139B2 JP H0420139 B2 JPH0420139 B2 JP H0420139B2 JP 10250684 A JP10250684 A JP 10250684A JP 10250684 A JP10250684 A JP 10250684A JP H0420139 B2 JPH0420139 B2 JP H0420139B2
- Authority
- JP
- Japan
- Prior art keywords
- carbon
- electrode
- solution
- graphite
- liquid junction
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 57
- 229910052799 carbon Inorganic materials 0.000 claims description 42
- 238000000034 method Methods 0.000 claims description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 229910002804 graphite Inorganic materials 0.000 claims description 8
- 239000010439 graphite Substances 0.000 claims description 8
- 239000000460 chlorine Substances 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 6
- 238000005259 measurement Methods 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 claims description 6
- 239000000843 powder Substances 0.000 claims description 6
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 claims description 6
- 239000007789 gas Substances 0.000 claims description 5
- 150000002500 ions Chemical class 0.000 claims description 5
- 239000004033 plastic Substances 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 4
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 3
- 239000002253 acid Substances 0.000 claims description 3
- 230000004913 activation Effects 0.000 claims description 3
- 229910052801 chlorine Inorganic materials 0.000 claims description 3
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 229910017604 nitric acid Inorganic materials 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 238000001816 cooling Methods 0.000 claims 1
- 239000000243 solution Substances 0.000 description 45
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 38
- 239000007788 liquid Substances 0.000 description 24
- 235000011164 potassium chloride Nutrition 0.000 description 19
- 239000001103 potassium chloride Substances 0.000 description 19
- 239000011521 glass Substances 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 7
- 239000012086 standard solution Substances 0.000 description 6
- XNGIFLGASWRNHJ-UHFFFAOYSA-N phthalic acid Chemical compound OC(=O)C1=CC=CC=C1C(O)=O XNGIFLGASWRNHJ-UHFFFAOYSA-N 0.000 description 4
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 2
- GTKRFUAGOKINCA-UHFFFAOYSA-M chlorosilver;silver Chemical compound [Ag].[Ag]Cl GTKRFUAGOKINCA-UHFFFAOYSA-M 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 2
- 229910052753 mercury Inorganic materials 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- BHWBMOFUXJUDJW-UHFFFAOYSA-N prop-1-ene hexahydrofluoride Chemical group CC=C.F.F.F.F.F.F BHWBMOFUXJUDJW-UHFFFAOYSA-N 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/301—Reference electrodes
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Physics & Mathematics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Molecular Biology (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Electrodes For Compound Or Non-Metal Manufacture (AREA)
Description
（産業上の利用分野）
本発明はPHおよび各種イオン濃度測定等に使用
する比較電極用のカーボン電極の製造方法に関す
るものである。
（発明の背景）
従来、PHおよびイオン濃度測定は、ガラス電極
と塩化加里（Ｋ Cl）の溶液を流出させる液絡部
を持つた比較電極を用いているが、この比較電極
には次のような欠点があつて、正確に測定ができ
なかつた。即ち、
(1) 液絡部より塩化加里溶液が流出しながら測定
するため、それが被測定溶液に混入し、そのPH
値に変化を起すこともあり、また化学反応を起
すこともある。
(2) 塩化加里溶液が液絡部を通じて被測定溶液に
接触する部分において液絡部電位差が生じる。
もともと比較電極としては液絡部電位差が無い
こと、或は被測定溶液の濃度の変化に対して
も、液絡部電位差が変化しないことが望しい。
しかし被測定溶液の濃度が上る（例えば酸性度
が強くなる）と、液絡部の電位差が大きくなる
傾向がある。例えば一般に25℃において中性標
準液6.865PHとフタル酸標準液4.008PHにて標準
較正を行い、修酸塩標準液1.679PHを測定した
場合、およそ0.04〜0.06PH以上の起電力誤差が
出てくる。
(3) 液絡部から塩化加里溶液が被測定溶液中に流
出するため、液絡部電位の安定に時間がかか
る。
(4) 一般に測定時において塩化加里溶液の補充孔
を開ける必要があり、一気圧で測定しなければ
ならない。そのため圧力の高い（又は低い）溶
液をそのまま測定すれば、被測定溶液が液絡部
を通じて塩化加里溶液中に逆流する。それによ
り液絡部電位差が変動することはいうまでもな
く、また圧力が低ければ塩化加里溶液の流出が
非常に早くなる。
(5) 最近は公害の理由で内部電極に水銀を用いる
甘汞電極の代りに、銀−塩化銀（Ag−Ag Cl）
電極を用いるようになつたが、銀−塩化銀は塩
化加里溶液、即ち高濃度の塩素イオン溶液によ
り溶出し、液絡部を詰まらせ、そのため当然な
がら液絡部の電位差が変動する。
(6) 塩化加里溶液が流出するため、当然補充を要
する。補充を怠ると塩化加里溶液だけが流出し
てなくなり、液絡部の液間電位差が変動した
り、又溶液全体が流出し、被測定溶液が液絡部
を通じて逆流する。従つて液間電位差が変動す
ることはいうまでもない。これは特に工業用の
時に多く起る。
以上の通り塩化加里溶液と液絡部とにより成る
比較電極は欠点が多にのにもかかわらず、それに
代わるべき新規な比較電極が提供されていなかつ
た。
（発明が解決しようとする問題点）
本発明は上記観点よりなされたもので、従来の
塩化加里溶液を液絡部より流出させるタイプのも
のと異なり、活性化処理を施したカーボン電極を
使用して、塩化加里溶液を流出させることなく、
PHおよびイオン濃度の測定ができる比較電極に使
用するカーボン電極の製造方法を提供することを
目的とする。
（発明の構成）
上記の目的を達成するため、本発明は次のよう
に構成されている。
すなわち、本発明は過塩素酸と硝酸と水との混
酸でグラフアイトを煮沸し、水洗い後泥状グラフ
アイトとし、更にこの泥状グラフアイトに四塩化
炭素を加え、塩素と窒素よりなる混合ガスを通過
させつつ加熱して後、窒素ガスのみを用いて更に
加熱後冷却してカーボン微粉末を得る第１工程
と、第１工程によつて得られたカーボン微粉末に
フツ素樹脂またはプラスチツク粉末を混合し、こ
の混合物をロールプレスし、または型に圧入して
所定の厚さに成型後冷却してカーボンシートまた
はカーボン棒を得る第２工程と、第２工程によつ
て得られたカーボンシート２枚またはカーボン棒
２本を各々極として稀硫酸溶液中で電解すること
により活性化処理を施してカーボン電極を得る第
３工程とにより製造されることを特徴として構成
されている。
（実施例）
本発明の好ましい実施例に就いて詳細に説明す
る。
比較電極に使用するカーボン電極を製造するた
めの第１工程としては先ずグラホイル等の市販グ
ラフアイトを、過塩素酸を１、硝酸（HNO3）を
３、水を３の割合とした混酸と共に、特に限定す
る必要はないが好ましくは２〜３時間煮沸させた
後、充分撹拌、水洗いして泥状にする。次にこの
泥状グラフアイトに等容量の四塩化炭素（Ｃ
Cl4）を加え、石英ボートに入れ、塩素（Cl2）ガ
ス１と窒素（N2）ガス10の容量の割合の混合ガ
スを通過させながら、グラフアイトを特に限定す
る必要はないが、好ましくは500℃位で凡そ２〜
３時間加熱する。この加熱後、窒素ガスのみを通
過させ、更に加熱温度を上げ、特に限定する必要
はないが好ましくは700〜900℃で５〜20分間加熱
した後冷却してカーボン微粉末を得て第１工程を
完了する。
次に第２工程としては第１工程によつて得られ
たカーボン微粉末フツ素を含むオレフインの重合
で得られる合成樹脂であるフツ素樹脂（例えば商
品名テフロン「デユポン社の登録商標」等）の粉
末又は六弗化プロピレン等の耐化学性、耐熱性、
防水性のあるプラスチツク粉末を、特に限定する
必要はないが好ましくは５〜10％混合して、この
混合物を常温〜300℃の温度でロールプレスをし、
または型に圧入して所定の厚さに成型後冷却して
カーボンシートまたはカーボン棒を得る。これに
よつて第２工程を完了する。
第３工程は、第２工程によつて得られたカーボ
ンシート又は棒を比較電極用カーボン電極に形成
する工程である。すなわち、前記第２工程によつ
て得られたカーボンシート２枚またはカーボン棒
２本を各々極として、１〜1.5Nの稀硫酸
（H2SO4）中で、特に限定する必要はないが好ま
しくは100μA〜２ｍＡ／cm2で直流電解を行い、５
〜10分毎に極性を切換えて、同様の条件で直流電
解を２〜10回繰返し、然る後水洗いして表面の洗
浄と活性化を行い、比較電極用カーボン電極を形
成するのである。
そして、前記本発明方法によつて得られたカー
ボン電極のうち膜状のものを使用して第１図に示
すような比較電極を形成した。すなわち、第１図
に示す比較電極は、薄いガラスまたはプラスチツ
ク製の支持管１の下方側に開口部２を穿設し、且
該開口部２に前記方法により製造されたカーボン
電極３を熱圧縮性チユーブ４により固着し内部溶
液５がもれないようにすると共に、カーボン電極
３の内部溶液５及び内部電極６に接触できるよう
にして形成されている。なお、図中７は内部電極
６の支持部であつて支持管１に固定されており、
また８はリード線であつて内部電極６に接続さ
れ、キヤツプ９を経て外部へ起電力を取り出すも
のである。
また、第２図に示すものは比較電極の他の実施
例であり、前記本発明方法によつて得られたカー
ボン電極のうち棒状のものを使用して作られた比
較電極である。すなわち、第２図に示す比較電極
は、薄いガラスまたはプラスチツク製の支持管１
の下方側に開口部２を穿設し、且該開口部２に前
記方法により製造された短かいカーボン電極３′
を接着剤４′により固着して形成され、その他の
構成は第１図のものと全く同一である。
ここで前記カーボン電極３，３′を使用した各
比較電極と従来タイプの比較電極（塩化加里溶液
と液絡部とにより成るもの）とを特性面に於いて
対比してみる。
従来測定せんとする溶液のPH値はガラス電極と
従来タイプの比較電極（塩化加里溶液と液絡部と
よりなるもの）間において起電力E1は理論的に
E1＝（PHｉ−PHｘ）α＋Eas＋Ej＋ΔEr ……(1)
で表されている。
PHｉ…ガラス電極の内部溶液のPH値、一般にPH
7.00である。
PHｘ…被測定溶液のPH値
α…0.1983T（ｍＶ／PH）、αはNernstの係数、Ｔ
は絶対温度である。
Eas…ガラス電極の真の不斉電位差
Ej…比較電極と被測定溶液間の液間電位差
ΔEr…ガラス電極の内部電極と比較電極の内部電
極間の電位差
(1)式で明らかな様にガラス電極の起電力は、Ej
がなければ、Nernstの係数に近い電位勾配（ｍ
Ｖ／PH）を示すものである。
これに対して、本発明方法により製造されたカ
ーボン電極を使用する第１図または第２図に示さ
れた比較電極とガラス電極間の起電力E2は
E2＝（PHｉ−PHｘ）α＋Eas−｛（PHi′
−PHｘ）β＋Eas′−ΔEr′｝ ……(2)
で表わされる。
PHｉ…ガラス電極の内部溶液のPH値、一般にPH
7.00である
PHｘ…被測定溶液のPH値
α…0.1983T（ｍＶ／PH）、αはNernstの係数、Ｔ
は絶対温度である
Eas…ガラス電極の真の不斉電位差
PHi′…カーボン電極をもつた比較電極の内部溶液
のPH値、一般にPH7.00でガラス電極の内部溶液
と同じものが望しい。
β…カーボン電極の起電力（ｍＶ／PH）で各PH値
において殆んど０に近いものである。
Eas′…カーボン電極をもつた比較電極の真の不斉
電位差
ΔEr′…カーボン電極をもつた比較電極の内部電
極とガラス電極の内部電極との電位差
今不斉電位差EasとEas′は極めて少いものであ
り、又当然変化も少い。また、ガラス電極の内部
溶液PHとカーボン電極をもつた比較電極の内部溶
液PH′は同様なものを用いるので、これによる電
位差は殆んどない。更にガラス電極とカーボン電
極をもつた比較電極の内部電極との電位差
ΔEr′も極めて少ないものである。即ち、内部溶
液と内部電極とも同様なものを用いるのであるか
ら少ない上に更に打消しになるためである。
以上の通りであるから、ガラス電極とカーボン
電極をもつた比較電極間の起電力E2はE2＝（PHｉ
−PHｘ）α…と考えてよくNernstの係数に近い
理想的な電極の組合せとなる。
次に各PH値を25℃において前記第１図に示すカ
ーボン電極をもつた比較電極を用いて測定した結
果は、第１表に示す如くであつて極めて安定なよ
い結果を与えている。
(Industrial Application Field) The present invention relates to a method for manufacturing a carbon electrode for a reference electrode used for measuring pH and various ion concentrations. (Background of the Invention) Conventionally, PH and ion concentration measurements have used a reference electrode that has a glass electrode and a liquid junction that allows a solution of potassium chloride (K Cl) to flow out. There were some shortcomings that made it impossible to measure accurately. That is, (1) Since the measurement is performed while the potassium chloride solution flows out from the liquid junction, it may mix into the solution to be measured and its pH may change.
It may cause a change in value, or it may cause a chemical reaction. (2) A potential difference occurs at the liquid junction where the potassium chloride solution contacts the solution to be measured through the liquid junction.
Originally, it is desirable for a reference electrode to have no potential difference at the liquid junction, or for the potential difference at the liquid junction to not change even when the concentration of the solution to be measured changes.
However, as the concentration of the solution to be measured increases (for example, the acidity increases), the potential difference at the liquid junction tends to increase. For example, if standard calibration is generally performed at 25°C with a neutral standard solution of 6.865PH and a phthalic acid standard solution of 4.008PH, and an oxalate standard solution of 1.679PH is measured, an electromotive force error of approximately 0.04 to 0.06PH or more will occur. come. (3) Since the potassium chloride solution flows out from the liquid junction into the measured solution, it takes time for the liquid junction potential to stabilize. (4) Generally, it is necessary to open a replenishment hole for potassium chloride solution during measurement, and measurements must be made at one atmosphere. Therefore, if a high (or low) pressure solution is directly measured, the solution to be measured flows back into the potassium chloride solution through the liquid junction. Needless to say, this causes a fluctuation in the potential difference at the liquid junction, and if the pressure is low, the potassium chloride solution will flow out very quickly. (5) Recently, silver-silver chloride (Ag-Ag Cl) has been used instead of the mercury electrode, which uses mercury as the internal electrode for pollution reasons.
Although electrodes have been used, silver-silver chloride is eluted by a potassium chloride solution, that is, a highly concentrated chlorine ion solution, and clogs the liquid junction, which naturally causes the potential difference across the liquid junction to fluctuate. (6) Potassium chloride solution will leak out, so it will naturally need to be replenished. If replenishment is neglected, only the potassium chloride solution will flow out and disappear, causing the liquid junction potential difference to fluctuate, or the entire solution will flow out, causing the solution to be measured to flow back through the liquid junction. Therefore, it goes without saying that the liquid junction potential difference varies. This often occurs especially in industrial applications. As described above, although the reference electrode composed of a potassium chloride solution and a liquid junction has many drawbacks, no new reference electrode has been provided to replace it. (Problems to be Solved by the Invention) The present invention has been made from the above viewpoint, and unlike the conventional type in which the potassium chloride solution flows out from the liquid junction, the present invention uses a carbon electrode subjected to an activation treatment. without spilling the potassium chloride solution.
The purpose of the present invention is to provide a method for manufacturing a carbon electrode used as a reference electrode capable of measuring pH and ion concentration. (Configuration of the Invention) In order to achieve the above object, the present invention is configured as follows. That is, in the present invention, graphite is boiled in a mixed acid of perchloric acid, nitric acid, and water, and after washing with water, it is made into muddy graphite, carbon tetrachloride is added to this muddy graphite, and a mixed gas consisting of chlorine and nitrogen is added. The first step is to heat the carbon powder while passing through it, then further heat and cool it using only nitrogen gas to obtain fine carbon powder, and add fluorine resin or plastic powder to the fine carbon powder obtained in the first step. a second step in which the mixture is roll-pressed or press-fitted into a mold to form a predetermined thickness and then cooled to obtain a carbon sheet or carbon rod; and a carbon sheet obtained in the second step. It is characterized in that it is manufactured by a third step of obtaining a carbon electrode by performing an activation treatment by electrolyzing two sheets or two carbon rods as electrodes in a dilute sulfuric acid solution. (Example) Preferred examples of the present invention will be described in detail. The first step for producing a carbon electrode used as a reference electrode is to first mix commercially available graphite such as graphoil with a mixed acid containing 1 part perchloric acid, 3 parts nitric acid (HNO 3 ), and 3 parts water. Although there is no particular limitation, it is preferable to boil for 2 to 3 hours, then thoroughly stir and wash with water to form a slurry. Next, an equal volume of carbon tetrachloride (C
Cl 4 ), placed in a quartz boat, and passing a mixed gas of 1 volume of chlorine (Cl 2 ) gas and 10 volumes of nitrogen (N 2 ) gas through the graphite, although it is not necessary to specifically limit it, it is preferable. is about 2~ at around 500℃
Heat for 3 hours. After this heating, only nitrogen gas is passed through, and the heating temperature is further raised, preferably at 700 to 900°C for 5 to 20 minutes, although there is no particular limitation, and then cooled to obtain carbon fine powder, which is the first step. complete. Next, as a second step, a fluororesin is a synthetic resin obtained by polymerizing the carbon fine powder obtained in the first step and an olefin containing fluorine (for example, trade name: Teflon "registered trademark of DuPont", etc.) Chemical resistance, heat resistance, such as powder or hexafluoride propylene,
Waterproof plastic powder is mixed, preferably 5 to 10%, though not particularly limited, and this mixture is roll pressed at a temperature of room temperature to 300°C,
Alternatively, it is press-fitted into a mold, molded to a predetermined thickness, and then cooled to obtain a carbon sheet or carbon rod. This completes the second step. The third step is a step of forming the carbon sheet or rod obtained in the second step into a carbon electrode for comparison electrode. That is, two carbon sheets or two carbon rods obtained in the second step are used as electrodes, and are preferably heated in dilute sulfuric acid (H 2 SO 4 ) of 1 to 1.5 N, although there is no need to specifically limit it. Perform direct current electrolysis at 100 μA to 2 mA/cm 2 , and
The polarity is switched every ~10 minutes and DC electrolysis is repeated 2 to 10 times under the same conditions, followed by washing with water to clean and activate the surface to form a carbon electrode for comparison. Then, a comparative electrode as shown in FIG. 1 was formed using a film-like carbon electrode obtained by the method of the present invention. That is, the reference electrode shown in FIG. 1 has an opening 2 formed at the lower side of a support tube 1 made of thin glass or plastic, and a carbon electrode 3 manufactured by the above method is placed in the opening 2 by heat compression. The inner solution 5 is fixed by the inner tube 4 to prevent the inner solution 5 from leaking, and is formed so as to be able to contact the inner solution 5 of the carbon electrode 3 and the inner electrode 6. In addition, 7 in the figure is a support part of the internal electrode 6, which is fixed to the support tube 1.
A lead wire 8 is connected to the internal electrode 6 and extracts the electromotive force to the outside through the cap 9. Moreover, what is shown in FIG. 2 is another example of a comparative electrode, which is a comparative electrode made using a rod-shaped carbon electrode obtained by the method of the present invention. That is, the reference electrode shown in FIG. 2 consists of a support tube 1 made of thin glass or plastic.
An opening 2 is formed in the lower side of the carbon electrode 3', and a short carbon electrode 3' manufactured by the above method is inserted into the opening 2.
The other structure is exactly the same as that shown in FIG. 1. Here, comparison electrodes using the carbon electrodes 3 and 3' will be compared with a conventional type comparison electrode (consisting of a potassium chloride solution and a liquid junction) in terms of characteristics. The PH value of the solution to be conventionally measured is the electromotive force E 1 between the glass electrode and the conventional comparison electrode (consisting of a potassium chloride solution and a liquid junction). Theoretically, E 1 = (PHi - PHx) α + Eas + Ej + ΔEr ...It is expressed as (1). PHi...PH value of the internal solution of the glass electrode, generally PH
It is 7.00. PHx...PH value of the solution to be measured α...0.1983T (mV/PH), α is Nernst's coefficient, T
is the absolute temperature. Eas...True asymmetric potential difference of the glass electrode Ej...Liquid junction potential difference between the reference electrode and the measured solution ΔEr...Potential difference between the internal electrode of the glass electrode and the internal electrode of the reference electrode As is clear from equation (1), the glass electrode The electromotive force is Ej
Otherwise, the potential gradient (m
V/PH). On the other hand, the electromotive force E 2 between the comparative electrode and the glass electrode shown in FIG. 1 or 2 using the carbon electrode manufactured by the method of the present invention is E 2 = (PHi−PHx)α+Eas− It is expressed as {(PHi′ −PHx)β+Eas′−ΔEr′} (2). PHi...PH value of the internal solution of the glass electrode, generally PH
PHx which is 7.00...PH value of the measured solution α...0.1983T (mV/PH), α is Nernst's coefficient, T
is the absolute temperature Eas...the true asymmetric potential difference of the glass electrode PHi'...the PH value of the internal solution of the reference electrode with a carbon electrode, generally PH7.00, which is preferably the same as the internal solution of the glass electrode. β... Electromotive force (mV/PH) of the carbon electrode, which is almost 0 at each PH value. Eas'...True asymmetric potential difference ΔEr' of the reference electrode with a carbon electrode...Potential difference between the internal electrode of the reference electrode with a carbon electrode and the internal electrode of the glass electrode.The asymmetric potential differences Eas and Eas' are extremely small. Of course, there are also few changes. Further, since the internal solution PH of the glass electrode and the internal solution PH' of the reference electrode having a carbon electrode are the same, there is almost no potential difference due to this. Furthermore, the potential difference ΔEr' between the internal electrode of the comparison electrode having a glass electrode and a carbon electrode is extremely small. That is, since the same internal solution and internal electrode are used, the amount is small and is further canceled out. As above, the electromotive force E 2 between the comparison electrode having a glass electrode and a carbon electrode is E 2 = (PHi
-PHx)α... This is an ideal combination of electrodes close to Nernst's coefficient. Next, each PH value was measured at 25° C. using a comparative electrode having a carbon electrode as shown in FIG. 1, and the results are as shown in Table 1, giving extremely stable and good results.
【表】
第１表中、
は25℃における標準液のPH値
は中性標準液6.865PHとフタル酸標準液4.008
PHとで標準較正をを行い、これを0.000PHとし
（実測では6.865PHと4.008間の起電力は１PHに
つき58.62ｍＶであつた）、各PH値における差を
示す。
上述のように本発明方法によつて得られた活性
化されたカーボン電極を使用した比較電極は、PH
およびイオン溶液濃度に対してその起電力がほと
んど変化がなく、また膜抵抗は数10Ω以下であ
る。従つて、従来タイプの塩化加里溶液と液絡部
を有する比較電極の液絡部抵抗は１〜10kΩであ
るため、この従来タイプの比較電極に代えて、本
発明方法によつて得られたカーボン電極を使用し
た比較電極を使用できることが裏付けられた。
（発明の効果）
本発明は上述のようであるから、従来タイプの
比較電極に代えて、本発明方法によつて得られた
カーボン電極を比較電極に用いることができるの
で、塩化加里溶液が流出することなく、その結果
塩化加里溶液が被測定液に混入せず、PH値に変化
を起すこともなく、また塩化加里溶液の補充が不
要で、極めて正確にPHおよびイオン濃度の測定が
可能である。[Table] In Table 1, indicates the PH value of the standard solution at 25℃. The neutral standard solution is 6.865PH and the phthalic acid standard solution is 4.008.
A standard calibration was performed with PH, and this was set to 0.000PH (in actual measurement, the electromotive force between 6.865PH and 4.008 was 58.62 mV per 1PH), and the difference in each PH value is shown. As described above, the reference electrode using the activated carbon electrode obtained by the method of the present invention has a PH
The electromotive force hardly changes with the ionic solution concentration, and the membrane resistance is several tens of ohms or less. Therefore, since the liquid junction resistance of a conventional type comparison electrode having a potassium chloride solution and a liquid junction is 1 to 10 kΩ, the carbon obtained by the method of the present invention should be used in place of this conventional type comparison electrode. It was confirmed that a comparison electrode using electrodes can be used. (Effects of the Invention) Since the present invention is as described above, the carbon electrode obtained by the method of the present invention can be used as a reference electrode instead of the conventional type of reference electrode, so that potassium chloride solution does not flow out. As a result, the potassium chloride solution does not mix with the liquid to be measured, there is no change in the PH value, and there is no need to replenish the potassium chloride solution, making it possible to measure PH and ion concentration extremely accurately. be.
第１図は本発明方法によつて得られた膜状のカ
ーボン電極を使用した比較電極の断面図、第２図
は同棒状のカーボン電極を使用した比較電極の断
面図である。
FIG. 1 is a cross-sectional view of a comparative electrode using a film-like carbon electrode obtained by the method of the present invention, and FIG. 2 is a cross-sectional view of a comparative electrode using the same rod-like carbon electrode.
Claims (1)
を煮沸し、水洗い後泥状グラフアイトとし、更に
この泥状グラフアイトに四塩化炭素を加え、塩素
と窒素よりなる混合ガスを通過させつつ加熱して
後、窒素ガスのみを用いて更に加熱後冷却してカ
ーボン微粉末を得る第１工程と、第１工程によつ
て得られたカーボン微粉末にフツ素樹脂またはプ
ラスチツク粉末を混合し、この混合物をロールプ
レスし、または型に圧入して所定の厚さに成型後
冷却してカーボンシートまたはカーボン棒を得る
第２工程と、第２工程によつて得られたカーボン
シート２枚またはカーボン棒２本を各々極として
稀硫酸溶液中で電解することにより活性化処理を
施してカーボン電極を得る第３工程とにより製造
されることを特徴とするPHおよびイオン濃度測定
に使用する比較電極用カーボン電極の製造方法。1. Graphite is boiled in a mixed acid of perchloric acid, nitric acid, and water, and after washing with water, it becomes muddy graphite. Furthermore, carbon tetrachloride is added to this muddy graphite, and a mixed gas consisting of chlorine and nitrogen is passed through it. A first step of heating and then heating and cooling using only nitrogen gas to obtain fine carbon powder; mixing fluororesin or plastic powder with the fine carbon powder obtained in the first step; A second step in which this mixture is roll-pressed or press-fitted into a mold to form a predetermined thickness and then cooled to obtain a carbon sheet or carbon rod; and two carbon sheets or carbon rods obtained in the second step. A reference electrode for use in pH and ion concentration measurements, characterized in that it is manufactured by a third step of obtaining a carbon electrode by performing an activation treatment by electrolyzing in a dilute sulfuric acid solution using two rods as electrodes. Method for manufacturing carbon electrodes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10250684A JPS60247150A (en) | 1984-05-23 | 1984-05-23 | Preparation of carbon electrode for reference electrode used in measurement of ph and ion concentration |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10250684A JPS60247150A (en) | 1984-05-23 | 1984-05-23 | Preparation of carbon electrode for reference electrode used in measurement of ph and ion concentration |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60247150A JPS60247150A (en) | 1985-12-06 |
| JPH0420139B2 true JPH0420139B2 (en) | 1992-03-31 |
Family
ID=14329282
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10250684A Granted JPS60247150A (en) | 1984-05-23 | 1984-05-23 | Preparation of carbon electrode for reference electrode used in measurement of ph and ion concentration |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS60247150A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ES2167258B2 (en) * | 2000-07-28 | 2003-03-01 | Univ Madrid Complutense | COMPOSITE AMPEROMETRIC BIOSENSOR FOR THE DETERMINATION OF CHOLESTEROL IN FOOD. |
-
1984
- 1984-05-23 JP JP10250684A patent/JPS60247150A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60247150A (en) | 1985-12-06 |
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