CA1058490A - Method of making an ion-selective electrode - Google Patents
Method of making an ion-selective electrodeInfo
- Publication number
- CA1058490A CA1058490A CA207,163A CA207163A CA1058490A CA 1058490 A CA1058490 A CA 1058490A CA 207163 A CA207163 A CA 207163A CA 1058490 A CA1058490 A CA 1058490A
- Authority
- CA
- Canada
- Prior art keywords
- solution
- ion
- membrane
- granules
- ag2s
- 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
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- 239000012528 membrane Substances 0.000 claims abstract description 50
- 150000002500 ions Chemical class 0.000 claims abstract description 38
- 239000008187 granular material Substances 0.000 claims abstract description 37
- 229910052946 acanthite Inorganic materials 0.000 claims abstract description 30
- FSJWWSXPIWGYKC-UHFFFAOYSA-M silver;silver;sulfanide Chemical compound [SH-].[Ag].[Ag+] FSJWWSXPIWGYKC-UHFFFAOYSA-M 0.000 claims abstract description 30
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 claims abstract description 21
- 229910052979 sodium sulfide Inorganic materials 0.000 claims abstract description 16
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims abstract description 16
- 229910052709 silver Inorganic materials 0.000 claims abstract description 14
- 239000004332 silver Substances 0.000 claims abstract description 14
- -1 silver halide Chemical class 0.000 claims abstract description 14
- 229910021607 Silver chloride Inorganic materials 0.000 claims abstract description 12
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 claims abstract description 12
- 238000000576 coating method Methods 0.000 claims abstract description 9
- 239000011248 coating agent Substances 0.000 claims abstract description 7
- ADZWSOLPGZMUMY-UHFFFAOYSA-M silver bromide Chemical compound [Ag]Br ADZWSOLPGZMUMY-UHFFFAOYSA-M 0.000 claims abstract description 7
- 238000006243 chemical reaction Methods 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 12
- 238000005530 etching Methods 0.000 claims description 5
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 claims description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 3
- XMBWDFGMSWQBCA-UHFFFAOYSA-N hydrogen iodide Chemical compound I XMBWDFGMSWQBCA-UHFFFAOYSA-N 0.000 claims description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims 1
- 229940006460 bromide ion Drugs 0.000 claims 1
- 229910017604 nitric acid Inorganic materials 0.000 claims 1
- 238000001556 precipitation Methods 0.000 claims 1
- 150000004820 halides Chemical class 0.000 abstract description 5
- 239000000243 solution Substances 0.000 description 40
- 239000000843 powder Substances 0.000 description 16
- 230000000694 effects Effects 0.000 description 7
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 6
- 239000012488 sample solution Substances 0.000 description 5
- 239000000460 chlorine Substances 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 229910004874 Na2S 9H2O Inorganic materials 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 229910052794 bromium Inorganic materials 0.000 description 3
- 229910052801 chlorine Inorganic materials 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000011780 sodium chloride Substances 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 238000000975 co-precipitation Methods 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 239000003822 epoxy resin Substances 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 229910052740 iodine Inorganic materials 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 1
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical class Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 239000011630 iodine Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 235000010333 potassium nitrate Nutrition 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 229910000679 solder Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
- 238000005406 washing Methods 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
- G01N27/333—Ion-selective electrodes or membranes
-
- 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
- G01N27/40—Semi-permeable membranes or partitions
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Biochemistry (AREA)
- General Physics & Mathematics (AREA)
- Electrochemistry (AREA)
- Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- Molecular Biology (AREA)
- General Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)
- Measuring Oxygen Concentration In Cells (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
- Electrodes For Compound Or Non-Metal Manufacture (AREA)
- Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method of making an ion-selective membrane of an ion-selective electrode, comprising the steps of coating surfaces of granules of a silver halide selected from the group consisting of AgCl, AgBr or AgI with an Ag2S layer by chemical reaction in Na2S solution and compressing the resultant granules to form a membrane. Fine granules of silver halide are formed by dropping AgNO3 solution into the solution of a halide of K or Na which is agitated strongly, for example, by a stirrer. The character-istics of the electrode are improved by using the granules coated with an Ag2S layer prepared by dropping the Na2S solution into the solution containing granules of strongly agitated silver halide.
A method of making an ion-selective membrane of an ion-selective electrode, comprising the steps of coating surfaces of granules of a silver halide selected from the group consisting of AgCl, AgBr or AgI with an Ag2S layer by chemical reaction in Na2S solution and compressing the resultant granules to form a membrane. Fine granules of silver halide are formed by dropping AgNO3 solution into the solution of a halide of K or Na which is agitated strongly, for example, by a stirrer. The character-istics of the electrode are improved by using the granules coated with an Ag2S layer prepared by dropping the Na2S solution into the solution containing granules of strongly agitated silver halide.
Description
~051~4~0 Method of Making an Ion-Selective Elec-trode This invention relates to a method of making`an ion-selective electrode, and more particularly to a method of making an ion-selective electrode for measuring ion activities such as Cl-, Br~ or I in solution Recently there have been developed some devices for measuring the ion activities using an ion-selective electrode, for example as disclosed in U.S. Patent No. 3,563,874.
Such an ion-selective electrode comprises a solid state electrode membrane. In the conventional art, the solid state electrode membrane is made by the co-precipitation method.
For example, for the ion-selective electrode for measuring the ion activities of Cl , Br or I , solution of Na2S 9H2O and halide of Na or K selected from the group of NaCl, ~Br and KI are mixed in the desired ratio, and the mixed solution is added to AgNO3 solution. Then there is formed a precipitated mixture of Ag2S and AgX (X is Cl, Br or I). The resultant mixed ~powder is compressed to form a tablet under high pressure, and the solid state membrane is provided. It is required, for these membranes to operate as means for measuring the ion activities in solution, that the granules of Ag2S and AgX are to be as fine as possible and to react with each other, to improve the characteristics of the ion-selective electrode. Also, presence of free ion and metal in the membrane should be avoided because it causes degradation of the characteristics of the ion-selective electrode, i.e. decrease of detecting sensitivity and delay of response time.
The conventional membrane of an ion-selective electrode is not completely desirable for this requirement.
For example, in the co-precipitation method, although the granules are very fine, all the granules are not reacted with ~ ' . .
.
each other because the probability that Ag2S is formed in-dependently is not zero.
Therefore, an object of the present invention is to provide a novel and improved method of making an ion-selective electrode membrane which is free from the con-ventional defects as described above.
A further object of the invention is to provide a method of making an ion-selective electrode having improved characteristics such as higher detecting sensitivity and faster response time.
A further object of the invention is to provide an improved method of making an ion-selective electrode easily by simple means and with low cost.
These objects are achieved by providing a method of making an ion-selective electrode according to the in-vention comprising the steps of: adding an AgNO3 solution to a solution of a chloride,bromide or iodide of Na or K which is kept agitated strongly so as to provide finer granules of a silver halide selected from the group consisting of AgC1, AgBr and AgI; coating the surface of said granules with a layer of Ag2S by chemical reaction in Na2S solution;
and compressing the resultant granules to form a membrane.
~ - 2 -These and other objects and the features of the invention will be apparent upon consideration of the following detailed description taken together with accompanying drawings, in which:
Fig. 1 is a schematic side-elevational, cross-sectional simplified view of the electrode made by the method of the invention; and Fig. 2 is a schematic side-elevational view of a cell employing the electrode of Fig. 1 for measurement of ion-activities in a sample solution.
Referring now to Fig. 1, the ion-selective elec-trode made by the method of the invention contains a solid state membrane designated by reference numeral 1. One surface of ., , .,, ~'.,.
.
:i - 2a -, ~ .
.:
. .
105~49~
the membrane 1 is coated with a conductive film 2 such as gold, silver, copper or nickel by the vacuum deposition method. A
metal plate 3, such as copper, is adhered on the conduction film 2 with conductive adhesive 4, and further the usual eoa~ial cable 5 is soldered to the copper plate 3 by solder 6. A
combination of the membrane 1 and the coaxial cable 5 is en-closed in an elogated hollow tubular eontainer 7, which is made by epoxy resin and open at both sides, at the lower open end thereof and adhered thereto with epoxy resin 8. An annular cap 10 is fitted with the other open end of the eontainer 7.
The cap 10 has an aperture through which the coaxial cable 5 is mounted. The outer surfaee 9 of the membrane 1, which contacts the sample solution, is polished with alumina powder of neàrly 0.05~ in particle size and washed by an ultrasonic cleaner in aleohol solution.
The membrane 1 of the eleetrode aecording to the present invention eonsist-of a powder of a silver halide seleeted from the group consisting of AgCl, AgBr and AgI according to the desired response of the eleetrode, the surfaee of the powder being eoated with layer of Ag2S whieh is formed in Na2S solution.
The powder eonsisting of Ag2S and silver halide is pressed so as to form the membrane 1. Further, the eharaeter-isties of the electrode ean be improved by etehing the surfaee of Ag2S layer inthe etehing solution sueh as ~iNO3 so as to aetivate the powder and then by erushin,gthe powder into finer granules.
Then the layer of Ag2S is formed on the surfaces of the granules by substitution reaetion in the solution of Na2S, and the resultant granules are pressed to form the membrane 1.
In the method of the present invention, silver halide is formed by putting AgNO3 solution into a solution of a halide of K or Na, and it is important that the solution of halide of .
- ---.. - , .. , ,~ , 10584gO
K or Na is kept agitated strongly so as to provide finer granules of silver halide.
The characteristics of the electrode membrane made by the method of the invention are dependent upon various factors such as the weight percentage ratio of Ag2S to the silver halide, etching condition of the powder, concentration and temperature of the solutions of I~NO3, AgNO3 and halide of K
or Na and coating time of the layer of Ag2S in Na2S solution.
The following are examples of the preparation of the membranes according to the invention, and the response of electrodes using such membranes.
Where the response is noted as being Nerns~an, it is intended to indicate that the ion-selective membrane responds substantially in accordance with well-known Nernst equation in a stable and reproducible manner.
The ion-selective electrode according to the invention responds stably as being Nernstian to lower ion activity in sample solution, and the response time is superior in the point of reproducibility.
Example 1.
0.1 mol/liter AgNO3 solution was dropped into a stoichiometric excess of 0.1 mol/liter NaCl solution which was strongly agitated by a stirrer, and the fine granules of AgCl of 10 gram were formed by chemical reaction.
Next, 0.1 mol/liter Na2S 9H2O solution was dropped into the solution containing these fine granules of AgCl which was agitated by a stirrer, and the surfaces of these granules of AgCl were coated with Ag2S layer in the solution according to the following chemical reaction:
2AgC14S) + Na2S(l) ~ Ag2S(S) + 2NaCl(l) At this time Na2S solution was added to the solution containing E~ .
105~3490 the granules of AgCl so as to get a ratio of Ag2S : AgCl = 50:
50 in wei~ht percentage. The resultant AgCl powders coated with ~g2S layer were washed in fresh distilled water about twenty times, and after washing they were dried ~L~r about one hour at a temperature of 80C to 100C in inert gas. The dried powders were crushed into fine granules by a usual crushing means.
Then the crushed powders weighin~ 10 grams were put into solution of 0.1 mol/liter Na2S 9H2O which was agitated by the stirrer, and the solution was kept agitated for ten minutes so that the surface of the crushed powders were again coated with an Ag2S layer. At this time the Na2S solution was used of a volume sufficient to get the ratio of Ag2S:AgCl = 60:40 in weight percentage. The resultant AgCl powders coated with Ag2S
layer were etched in 0.1 mol/liter Hi~03 solution for about two minutes, and after being washed in fresh distilled water, they were dried at a temperature of 80C to 100C in inert gas.
These final powders contained substantially no free metal and no free metal ions such as Ag. Then the final powder was pressed, for example under 10 tons/cm2 in a die having a diameter of 10 mm, for several minutes at room tem-perature in air to form a tablet or a membrane.
Using the membrane made as described above, the ion-selective electrode as shown in Fig. 1 was constructed. Fig. 2 shows a schematic diagram of a device for measuring the ion-activities in a solution by using the electrode 11 of Fi~. 1.
The electrode 11 is placed in a sample solution 13 under test so that the outer surface 9 of the membrane 1 contacts the solution 13. A standard reference electrode, such as a saturated calomel electrode, is also placed in contact with 30 the solution 13. The two electrodes 11 and 12 are connected to a voltmeter 14, by which the potential developed by the electrode 11 in the sample solution is measured, together with the reference electrode 12. The potential En is developed according to the well known Nernst equation:
RT
En = Eo + ~ ln C
nF
where Eo, R, T and F are the usual well-known values, and C represents the ion activities. Usually, the term RT/nF is called Nernst's constant, and its value is 59.2 mV for a univalent ion such as Cl-. The membrane is made according to the method as described hereinbefore.
With the ion-selective electrode using the membrane, ~ -ion activities of chlorine in a number of aqueous solutions of KCl having different concentrations diluted precisely and serially were measured, respectively.
Then, ion-strength in these solution were adgusted by 0.1 mol/liter KNO3 solution, respectively. The measured potentials with this electrode areshown in the following Table 1 for each RCl solution of the different concentrations.
Table 1 , .~ . .. _ . _ ; Conc. of Cl in ml/liter ~ 10 10 10 4 10 5 10 6 . . .
Potentials (mV) 15 74 133192 239 254 . . _ . ._ The dynamic response time of the electrode was as shown in Table 2, where the concentration of solutions were hastily changed from low concentration to high concentration, and the solution was kept agitated for measuring the dynamic response time.
Ta~le 2 ¦Change of Conc. (mol~llter) ¦10-5 ~ 10-~¦10 4 ~ 10 . ~ _ _ Dynamic Response time (Sec) 1 ~ 0.5 . . _ ._ _ J
.
. . .
~OS8490 Examplc 2 A membrane was made by a slmilar method as described in Example 1, except that KBr solution was used instead of the NaCl solution, and that the powders of AgBr coated with Ag2S layer at the first coating process were put into 0.05 mol~
liter Na2S solution at the second coating process. Similarly to Example 1, the ion-activities of bromine in a number of aqueous solution of KBr of different concentrations were measured.
Table 3 shows the measured potentials developed by the electrodes containing the membrane made as described above, which consist of the granules of AgBr having surface coated with Ag2S.
Table 3 _ ~
Conc. of Br in /liter 10 10 10 10 10 10 10 Potentials (mV) 2 61 121 180 239 291 310 , ,,, ,,~
Example 3 ; A membrane was made by a similar method as described in Example 2, except that KI solution was used instead of the KBr solution.
Similarly to ~xample 1, tlle ion-activities o~ iodine in a number of aqueous solution of KI of different concentrations were measured.
` Table 4 shows the measured potentials developed by the electrodes containing the membrane made as described above, which consist of the granules of AgI having surfaces coated with Ag2S
Table 4 . ._ ._ Conc. of I in mVlite _ _ _ _ Potentials (mV) -48 11 70 129 139 247 307 353 :: .
Such an ion-selective electrode comprises a solid state electrode membrane. In the conventional art, the solid state electrode membrane is made by the co-precipitation method.
For example, for the ion-selective electrode for measuring the ion activities of Cl , Br or I , solution of Na2S 9H2O and halide of Na or K selected from the group of NaCl, ~Br and KI are mixed in the desired ratio, and the mixed solution is added to AgNO3 solution. Then there is formed a precipitated mixture of Ag2S and AgX (X is Cl, Br or I). The resultant mixed ~powder is compressed to form a tablet under high pressure, and the solid state membrane is provided. It is required, for these membranes to operate as means for measuring the ion activities in solution, that the granules of Ag2S and AgX are to be as fine as possible and to react with each other, to improve the characteristics of the ion-selective electrode. Also, presence of free ion and metal in the membrane should be avoided because it causes degradation of the characteristics of the ion-selective electrode, i.e. decrease of detecting sensitivity and delay of response time.
The conventional membrane of an ion-selective electrode is not completely desirable for this requirement.
For example, in the co-precipitation method, although the granules are very fine, all the granules are not reacted with ~ ' . .
.
each other because the probability that Ag2S is formed in-dependently is not zero.
Therefore, an object of the present invention is to provide a novel and improved method of making an ion-selective electrode membrane which is free from the con-ventional defects as described above.
A further object of the invention is to provide a method of making an ion-selective electrode having improved characteristics such as higher detecting sensitivity and faster response time.
A further object of the invention is to provide an improved method of making an ion-selective electrode easily by simple means and with low cost.
These objects are achieved by providing a method of making an ion-selective electrode according to the in-vention comprising the steps of: adding an AgNO3 solution to a solution of a chloride,bromide or iodide of Na or K which is kept agitated strongly so as to provide finer granules of a silver halide selected from the group consisting of AgC1, AgBr and AgI; coating the surface of said granules with a layer of Ag2S by chemical reaction in Na2S solution;
and compressing the resultant granules to form a membrane.
~ - 2 -These and other objects and the features of the invention will be apparent upon consideration of the following detailed description taken together with accompanying drawings, in which:
Fig. 1 is a schematic side-elevational, cross-sectional simplified view of the electrode made by the method of the invention; and Fig. 2 is a schematic side-elevational view of a cell employing the electrode of Fig. 1 for measurement of ion-activities in a sample solution.
Referring now to Fig. 1, the ion-selective elec-trode made by the method of the invention contains a solid state membrane designated by reference numeral 1. One surface of ., , .,, ~'.,.
.
:i - 2a -, ~ .
.:
. .
105~49~
the membrane 1 is coated with a conductive film 2 such as gold, silver, copper or nickel by the vacuum deposition method. A
metal plate 3, such as copper, is adhered on the conduction film 2 with conductive adhesive 4, and further the usual eoa~ial cable 5 is soldered to the copper plate 3 by solder 6. A
combination of the membrane 1 and the coaxial cable 5 is en-closed in an elogated hollow tubular eontainer 7, which is made by epoxy resin and open at both sides, at the lower open end thereof and adhered thereto with epoxy resin 8. An annular cap 10 is fitted with the other open end of the eontainer 7.
The cap 10 has an aperture through which the coaxial cable 5 is mounted. The outer surfaee 9 of the membrane 1, which contacts the sample solution, is polished with alumina powder of neàrly 0.05~ in particle size and washed by an ultrasonic cleaner in aleohol solution.
The membrane 1 of the eleetrode aecording to the present invention eonsist-of a powder of a silver halide seleeted from the group consisting of AgCl, AgBr and AgI according to the desired response of the eleetrode, the surfaee of the powder being eoated with layer of Ag2S whieh is formed in Na2S solution.
The powder eonsisting of Ag2S and silver halide is pressed so as to form the membrane 1. Further, the eharaeter-isties of the electrode ean be improved by etehing the surfaee of Ag2S layer inthe etehing solution sueh as ~iNO3 so as to aetivate the powder and then by erushin,gthe powder into finer granules.
Then the layer of Ag2S is formed on the surfaces of the granules by substitution reaetion in the solution of Na2S, and the resultant granules are pressed to form the membrane 1.
In the method of the present invention, silver halide is formed by putting AgNO3 solution into a solution of a halide of K or Na, and it is important that the solution of halide of .
- ---.. - , .. , ,~ , 10584gO
K or Na is kept agitated strongly so as to provide finer granules of silver halide.
The characteristics of the electrode membrane made by the method of the invention are dependent upon various factors such as the weight percentage ratio of Ag2S to the silver halide, etching condition of the powder, concentration and temperature of the solutions of I~NO3, AgNO3 and halide of K
or Na and coating time of the layer of Ag2S in Na2S solution.
The following are examples of the preparation of the membranes according to the invention, and the response of electrodes using such membranes.
Where the response is noted as being Nerns~an, it is intended to indicate that the ion-selective membrane responds substantially in accordance with well-known Nernst equation in a stable and reproducible manner.
The ion-selective electrode according to the invention responds stably as being Nernstian to lower ion activity in sample solution, and the response time is superior in the point of reproducibility.
Example 1.
0.1 mol/liter AgNO3 solution was dropped into a stoichiometric excess of 0.1 mol/liter NaCl solution which was strongly agitated by a stirrer, and the fine granules of AgCl of 10 gram were formed by chemical reaction.
Next, 0.1 mol/liter Na2S 9H2O solution was dropped into the solution containing these fine granules of AgCl which was agitated by a stirrer, and the surfaces of these granules of AgCl were coated with Ag2S layer in the solution according to the following chemical reaction:
2AgC14S) + Na2S(l) ~ Ag2S(S) + 2NaCl(l) At this time Na2S solution was added to the solution containing E~ .
105~3490 the granules of AgCl so as to get a ratio of Ag2S : AgCl = 50:
50 in wei~ht percentage. The resultant AgCl powders coated with ~g2S layer were washed in fresh distilled water about twenty times, and after washing they were dried ~L~r about one hour at a temperature of 80C to 100C in inert gas. The dried powders were crushed into fine granules by a usual crushing means.
Then the crushed powders weighin~ 10 grams were put into solution of 0.1 mol/liter Na2S 9H2O which was agitated by the stirrer, and the solution was kept agitated for ten minutes so that the surface of the crushed powders were again coated with an Ag2S layer. At this time the Na2S solution was used of a volume sufficient to get the ratio of Ag2S:AgCl = 60:40 in weight percentage. The resultant AgCl powders coated with Ag2S
layer were etched in 0.1 mol/liter Hi~03 solution for about two minutes, and after being washed in fresh distilled water, they were dried at a temperature of 80C to 100C in inert gas.
These final powders contained substantially no free metal and no free metal ions such as Ag. Then the final powder was pressed, for example under 10 tons/cm2 in a die having a diameter of 10 mm, for several minutes at room tem-perature in air to form a tablet or a membrane.
Using the membrane made as described above, the ion-selective electrode as shown in Fig. 1 was constructed. Fig. 2 shows a schematic diagram of a device for measuring the ion-activities in a solution by using the electrode 11 of Fi~. 1.
The electrode 11 is placed in a sample solution 13 under test so that the outer surface 9 of the membrane 1 contacts the solution 13. A standard reference electrode, such as a saturated calomel electrode, is also placed in contact with 30 the solution 13. The two electrodes 11 and 12 are connected to a voltmeter 14, by which the potential developed by the electrode 11 in the sample solution is measured, together with the reference electrode 12. The potential En is developed according to the well known Nernst equation:
RT
En = Eo + ~ ln C
nF
where Eo, R, T and F are the usual well-known values, and C represents the ion activities. Usually, the term RT/nF is called Nernst's constant, and its value is 59.2 mV for a univalent ion such as Cl-. The membrane is made according to the method as described hereinbefore.
With the ion-selective electrode using the membrane, ~ -ion activities of chlorine in a number of aqueous solutions of KCl having different concentrations diluted precisely and serially were measured, respectively.
Then, ion-strength in these solution were adgusted by 0.1 mol/liter KNO3 solution, respectively. The measured potentials with this electrode areshown in the following Table 1 for each RCl solution of the different concentrations.
Table 1 , .~ . .. _ . _ ; Conc. of Cl in ml/liter ~ 10 10 10 4 10 5 10 6 . . .
Potentials (mV) 15 74 133192 239 254 . . _ . ._ The dynamic response time of the electrode was as shown in Table 2, where the concentration of solutions were hastily changed from low concentration to high concentration, and the solution was kept agitated for measuring the dynamic response time.
Ta~le 2 ¦Change of Conc. (mol~llter) ¦10-5 ~ 10-~¦10 4 ~ 10 . ~ _ _ Dynamic Response time (Sec) 1 ~ 0.5 . . _ ._ _ J
.
. . .
~OS8490 Examplc 2 A membrane was made by a slmilar method as described in Example 1, except that KBr solution was used instead of the NaCl solution, and that the powders of AgBr coated with Ag2S layer at the first coating process were put into 0.05 mol~
liter Na2S solution at the second coating process. Similarly to Example 1, the ion-activities of bromine in a number of aqueous solution of KBr of different concentrations were measured.
Table 3 shows the measured potentials developed by the electrodes containing the membrane made as described above, which consist of the granules of AgBr having surface coated with Ag2S.
Table 3 _ ~
Conc. of Br in /liter 10 10 10 10 10 10 10 Potentials (mV) 2 61 121 180 239 291 310 , ,,, ,,~
Example 3 ; A membrane was made by a similar method as described in Example 2, except that KI solution was used instead of the KBr solution.
Similarly to ~xample 1, tlle ion-activities o~ iodine in a number of aqueous solution of KI of different concentrations were measured.
` Table 4 shows the measured potentials developed by the electrodes containing the membrane made as described above, which consist of the granules of AgI having surfaces coated with Ag2S
Table 4 . ._ ._ Conc. of I in mVlite _ _ _ _ Potentials (mV) -48 11 70 129 139 247 307 353 :: .
Claims (10)
1. A method of making an ion-selective membrane of an ion-selective electrode, comprising the steps of:
adding an AgNO3 solution to a solution of a chloride, bromide or iodide of Na or K which is kept agitated strongly so as to provide finer granules of a silver halide selected from the group consisting of AgCl, AgBr and AgI; coating the surface of said granules with a layer of Ag2S by chemical reaction in Na2S solution; and compressing the resultant granules to form a membrane.
adding an AgNO3 solution to a solution of a chloride, bromide or iodide of Na or K which is kept agitated strongly so as to provide finer granules of a silver halide selected from the group consisting of AgCl, AgBr and AgI; coating the surface of said granules with a layer of Ag2S by chemical reaction in Na2S solution; and compressing the resultant granules to form a membrane.
2. A method of making an ion-selective membrane as claimed in claim 1, wherein said membrane is made by coating the surface of AgCl granules with an Ag2S layer in Na2S solution and compressing the resultant granules to form a membrane, said membrane being responsive to chloride ions in solution.
3. A method of making an ion-selective membrane as claimed in claim 1, wherein said membrane is made by coating the surface of AgBr granules with an Ag2S layer in Na2S solution and compressing the resultant granules to form a membrane, said membrane being responsive to bromide ion in solution.
4. A method of making an ion-selective membrane as claimed in claim 1, wherein said membrane is made by coating the surface of AgI granules with an Ag2S layer in Na2S solution and compressing the resultant granules to form a membrane, said membrane being responsive to iodide ions in solution.
5. A method of making an ion-selective membrane as claimed in claim 1, wherein said granules of silver halide are made by the precipitation method and are coated with an Ag2S layer by dropping the Na2S solution into the solution containing said granules of the silver halide.
6. A method of making an ion-selective membrane as claimed in claim 1, wherein before said compressing step, said silver halide coated with Ag2S layer is crushed into finer granules, and the thus made finer granules are further coated with a further Ag2S layer by further chemical reaction in Na2S solution.
7. A method of making an ion-selective membrane as claimed in claim 6, wherein said finer granules coated with said further Ag2S layer are etched in an etching solution before said compressing step.
8. A method of making an ion-selective membrane as claimed in claim 7, wherein said etching solution is HNO3 solution.
9. A method of making an ion-selective membrane as claimed in claim 1, wherein said granules coated with said layer of Ag2S are etched in an etching solution before said compressing step.
10. A method of making an ion-selective membrane as claimed in claim 9, wherein said etching solution is NHO3 solution.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13848973A JPS547478B2 (en) | 1973-12-10 | 1973-12-10 | |
| JP13848873A JPS5419279B2 (en) | 1973-12-10 | 1973-12-10 | |
| JP13849273A JPS547479B2 (en) | 1973-12-10 | 1973-12-10 | |
| JP13849173A JPS5419280B2 (en) | 1973-12-10 | 1973-12-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1058490A true CA1058490A (en) | 1979-07-17 |
Family
ID=27472144
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA207,163A Expired CA1058490A (en) | 1973-12-10 | 1974-08-16 | Method of making an ion-selective electrode |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1058490A (en) |
| FR (1) | FR2253847B1 (en) |
| GB (1) | GB1474716A (en) |
| IT (1) | IT1032155B (en) |
| SE (1) | SE418906B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103308581A (en) * | 2013-06-04 | 2013-09-18 | 郑静雨 | Method for preparing iodine ion selective electrode crystal film by employing high-temperature melting method |
-
1974
- 1974-08-16 CA CA207,163A patent/CA1058490A/en not_active Expired
- 1974-09-12 FR FR7430926A patent/FR2253847B1/fr not_active Expired
- 1974-12-06 IT IT54393/74A patent/IT1032155B/en active
- 1974-12-09 SE SE7415384A patent/SE418906B/en not_active IP Right Cessation
- 1974-12-10 GB GB5343474A patent/GB1474716A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| SE418906B (en) | 1981-06-29 |
| FR2253847A1 (en) | 1975-07-04 |
| SE7415384L (en) | 1975-06-11 |
| DE2431288B2 (en) | 1976-01-22 |
| DE2431288A1 (en) | 1975-06-19 |
| IT1032155B (en) | 1979-05-30 |
| GB1474716A (en) | 1977-05-25 |
| FR2253847B1 (en) | 1976-10-22 |
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