US3223609A - Hygrometer - Google Patents
Hygrometer Download PDFInfo
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- US3223609A US3223609A US148442A US14844261A US3223609A US 3223609 A US3223609 A US 3223609A US 148442 A US148442 A US 148442A US 14844261 A US14844261 A US 14844261A US 3223609 A US3223609 A US 3223609A
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- rhodium
- cell
- electrodes
- hygrometer
- electrolytic
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- 239000010948 rhodium Substances 0.000 claims description 48
- 229910052703 rhodium Inorganic materials 0.000 claims description 47
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 47
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 32
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 23
- 239000001257 hydrogen Substances 0.000 description 23
- 229910052739 hydrogen Inorganic materials 0.000 description 23
- 229910052697 platinum Inorganic materials 0.000 description 16
- 239000004020 conductor Substances 0.000 description 13
- 230000006798 recombination Effects 0.000 description 11
- 238000005215 recombination Methods 0.000 description 11
- 239000000126 substance Substances 0.000 description 11
- 239000011810 insulating material Substances 0.000 description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 238000000034 method Methods 0.000 description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- 239000010408 film Substances 0.000 description 4
- 238000007747 plating Methods 0.000 description 4
- 229910000629 Rh alloy Inorganic materials 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 230000005923 long-lasting effect Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- -1 polychlorotrifluoroethylene Polymers 0.000 description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 description 3
- 229940058401 polytetrafluoroethylene Drugs 0.000 description 3
- 229910001260 Pt alloy Inorganic materials 0.000 description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 2
- YWEUIGNSBFLMFL-UHFFFAOYSA-N diphosphonate Chemical compound O=P(=O)OP(=O)=O YWEUIGNSBFLMFL-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- DLYUQMMRRRQYAE-UHFFFAOYSA-N phosphorus pentoxide Inorganic materials O1P(O2)(=O)OP3(=O)OP1(=O)OP2(=O)O3 DLYUQMMRRRQYAE-UHFFFAOYSA-N 0.000 description 2
- 150000003058 platinum compounds Chemical class 0.000 description 2
- 238000004382 potting Methods 0.000 description 2
- 229910000679 solder Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 229920001169 thermoplastic Polymers 0.000 description 2
- 239000004416 thermosoftening plastic Substances 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910000575 Ir alloy Inorganic materials 0.000 description 1
- LVDRREOUMKACNJ-BKMJKUGQSA-N N-[(2R,3S)-2-(4-chlorophenyl)-1-(1,4-dimethyl-2-oxoquinolin-7-yl)-6-oxopiperidin-3-yl]-2-methylpropane-1-sulfonamide Chemical compound CC(C)CS(=O)(=O)N[C@H]1CCC(=O)N([C@@H]1c1ccc(Cl)cc1)c1ccc2c(C)cc(=O)n(C)c2c1 LVDRREOUMKACNJ-BKMJKUGQSA-N 0.000 description 1
- 244000273256 Phragmites communis Species 0.000 description 1
- 235000014676 Phragmites communis Nutrition 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229940045985 antineoplastic platinum compound Drugs 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- PXXKQOPKNFECSZ-UHFFFAOYSA-N platinum rhodium Chemical compound [Rh].[Pt] PXXKQOPKNFECSZ-UHFFFAOYSA-N 0.000 description 1
- 229920002493 poly(chlorotrifluoroethylene) Polymers 0.000 description 1
- 239000005023 polychlorotrifluoroethylene (PCTFE) polymer Substances 0.000 description 1
- 150000003283 rhodium Chemical class 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
Images
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
- G01N27/416—Systems
- G01N27/42—Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte
- G01N27/423—Coulometry
Definitions
- Electrolytic hygrometers have been widely used for determining the moisture content of fluid streams in industrial processes in which the presence of even minute percentages of moisture is of great significance.
- This type of hygrometer has numerous advantages over other moisture determining devices, particularly when used in conjunction with continuous process streams, as it is quite selective to water, has a rapid speed of response, and is completely quantitative over wide ranges of moisture concentration, thereby eliminating the need for frequent calibration and standard samples.
- Electrolytic hygrometers depend for their operation on the relationship between the amount of water present in a hygroscopic substance and the amount of current necessary to electrolyze it.
- the active elements of the most commonly available hygrometers comprise a pair of helical platinum conductors partially embedded in a supporting tubular jacket, the interior of which is coated with a hygroscopic substance which bridges the spaces between adjacent turns of the helixes.
- the gas or vapor to be tested is passed over the hygroscopic substance which absorbs the moisture present in the gas or vapor and becomes conductive.
- An electric current is then passed between the adjacent turns of the two platinum conductors and the water is electrolyzed to hydrogen and oxygen.
- the amount of current necessary to completely electrolyze the water is, of course, a measure of the moisture content of the fluid beihg tested.
- an electrolitic hygrometer cell may be provided that has an extremely long life expectancy and which may be used with equal facility on streams containing any percentage of hydrogen.
- the important advantage of long life expectancy may be obtained by providing the cell with at least one rhodium electrode which serves as the anode when the cell is operatively connected in an appropriate electrical circuit.
- the anode should be rhodium and the cathode should be a conductor which does not catalyze the recombination of hydrogen and oxygen. Both electrodes may be rhodium for this application.
- FIG. 1 is a sectional view of one type of active element of an electrolytic hygrometer cell incorporating the teachings of the present invention
- FIG. 2 is a view partly in section of a portion of an electrolytic hygrometer cell according to the present invention
- FIG. 3 is a view partly in section of an electrolytic hygrometer cell according to the present invention.
- FIG. 4 is a sectional view of another form of active element of an electrolytic hygrometer cell incorporating the teachings of the present invention.
- FIG. 5 is a schematic showing of an electrical circuit used to form an electrolytic hygrometer cell in accordance with one aspect of the present invention.
- FIG. 6 is a sectional view of a portion of another form of active element of an electrolytic hygrometer cell incorporating the teachings of the present invention.
- an active element which comprises a pair of helically wound, substantially pure rhodium electrodes 12 and 14 partially embedded in a jacket 16 of a suitable insulating material, "for example, a thermoplastic resin such as polychlorotrifluoroethylene. If desired, this jacket may be constructed of glass or another suitable material.
- a suitable insulating material for example, a thermoplastic resin such as polychlorotrifluoroethylene. If desired, this jacket may be constructed of glass or another suitable material.
- the unembedded or active portions of the rhodium electrodes 12 and 14 make up a portion of the surface of an interior annular passageway 18 extending through the thermoplastic jacket 16.
- the electrodes 12 and 14 terminate in a pair of conductors 20 and 22 which protrude outwardly from the end of the thermoplastic jacket 16 so that the electrodes may be connected into a suitable electrical circuit.
- the annular surface of the interior passageway 18 through the jacket 16 is coated with a thin film of a suitable hygroscopic substance, for example, phosphorus pentoxide, so that each segment of insulating material separating alternate active portions of the rhodium electrodes 12 and 14 is bridged by a material which may become conductive.
- the active element just described is preferably made in accordance with the teachings of U.S. application Serial No. 134,506, filed August 28, 1961, by Douglas B. Gardner and assigned to the assignee of the present application. Briefly, this element is made by spacewinding the electrodes 12 and 14 on a stainless steel mandrel, extruding the jacket 16 over the mandrel and the electrodes, removing the mandrel, peeling the jacket back to expose the ends of the electrodes, and passing a slurry of phosphoric acid through the annular passageway previously occupied by the mandrel to form the bridging film of phosphorus pentoxide.
- rhodium as the electrode material vastly extends the useful life of an electrolytic cell. Tests indicate that the life expectancy of an electrolytic cell utilizing rhodium electrodes is well over 500,000 part per millionhours in contrast with the aforementioned 40,000 part per million-hours for cells utilizing platinum electrodes. It has been found that when substantially pure rhodium electrodes are used, the inter-electrode deposits previously referred to are completely or nearly completely eliminated.
- rhodium electrodes into an electrolytic cell enables it to be used to accurately measure the moisture content of gas or vapor streams, regardless of their hydrogen content.
- the rhodium electrodes themselves do not appear to catalyze the recombination of liberated oxygen and hydrogen as do platinum electrodes when they are employed in a similar environment and, moreover, no interelectrode deposits are formed which might act as a catalyst for this reaction.
- the recombination, if any, that takes place is insignificant, and the only water electrolyzed is that which enters the cell in the gas or vapor stream.
- the electrodes need not be of substantially pure rhodium but may be composed of an alloy of rhodium. These alloys, however, do not extend the life of a cell as greatly as does substantially pure rhodium. For example, an alloy of 60 percent platinum and 40 percent rhodium was found to increase the life of a cell by approximately a factor of over a cell having platinum electrodes. This example is, of course, strictly illustrative, as any alloy having a rhodium content not substantially less than 40 percent will be useful, for example, alloys of rhodium and iridium or osmium as well as other alloys of platinum and rhodium will appreciably increase cell life.
- the electrode which serves as the anode in the electrolysis need be of rhodium to prevent the deposition of inter-electrode deposits.
- the use of a pair of rhodium electrodes is, however, preferred because the use of a single electrode requires that one terminal of the cell be always positive, thus decreasing its convenience and adaptability in use;
- the presence of the platinum electrode would somewhat increase the recombination rate of liberated oxygen and hydrogen if the cell were used on a hydrogen stream, thus making it less attractive for this use.
- the presence of platinum in a rhodium-platinum alloy would also have this effect on a hydrogen stream.
- FIGS. 2 and 3 there is shown a complete electrolytic cell incorporating an active element similar to that shown in FIG. 1.
- the conductors 20 and 22 protrude from the end of the element 10 and are bent back over the jacket at an angle of 180 and held snugly against the jacket by means of a sleeve 26, preferably of polytetrafiuoroethylene.
- the extremeties of the rhodium conductors 20 and 22 are joined to a pair of copper conductors 28 and 30, in any suitable fashion, for example, by means of solder 32.
- thermofitting plastic tube 34 which, together with the polytetrafluor oethylene sleeve 26, prevents movement of the somewhat delicate rhodium conductors 20 and 22 and thereby protects them from being broken during the assembly and use of the cell.
- a suitable length of active element 10 is coiled in any desired manner, for instance,
- the casing 36 is provided with a pair of ports 38 and 40 which are sealed by a pair of insulating members 42 and 44 made of any suitable material. As shown, these members take the form of commercial metal to glass hermetic feed-through termirials.
- the insulators 42 and 44 are provided with annular passageways 46 and 48 for the passage of conductors 28 and 30 therethrough from the active element in the interior of the casing 36 to the point where they may be connected into an appropriate indicating circuit.
- one end of the casing 36 is closed by means of a steel washer 52 that rests upon a shoulder 54 provided on the inner surface of the casing 36.
- a polytetrafiuoroethylene plug 56 having a slightly tapered interior passageway is then inserted into the end and seated on the washer 52 and the seal is then completed by passing a polytetrafluoroethylene sleeve 58 over the end of the active element 10 and forcing it against the taper of the passageway in the plug 56 until it is firmly seated.
- the interior of the casing 36 is then filled with a suitable potting compound 60, care being taken that none of the potting compound blocks the open end of the element 10.
- the resulting structure is a durable, long-lasting electrolytic hygrometer cell that can be used with equal effect on streams having high or low hydrogen contents.
- FIG. 4 there is shown another type of active element that may incorporate the teachings of the present invention.
- This type element is made by wrapping a pair of rhodium electrodes separated by a pair of copper spacer windings around a mandrel and extruding a suitable jacket e.g., of polytetrafluoroethylene over the wires and the mandrel. The mandrel is then removed and the copper spacer windings etched away. The surface of the annular passageway formed by the removal of the mandrel is then coated with a thin film of a suitable hygroscopic substance.
- This type element can be incorporated into the cells shown in FIG. 3 in place of the element 10.
- the use of rhodium in place of platinum for the electrodes in this type of cell element also increases its life in the same fashion as previously described.
- FIG. 5 A circuit suitable for such a process is shown in FIG. 5.
- a suitable cell 70 is shown from which extends a pair of conductors 72 and 74 through a pair of insulating members 76 and 78.
- the active element of the cell in this figure is constructed with platinum electrodes and may be formed in the manner shown in FIGS. 1 or 4 or in any other suitable fashion.
- the conductors 72 and 74 are connected in a series circuit with a suitable source of voltage 80, a variable resistor 82, an ammeter 84, and a switch 86.
- a commercial rhodium plating solution is then introduced into the active element through a conduit 88 and the switch 86 closed.
- the resulting voltage across the two cell electrodes causes the electrode connected as the cathode to be plated with rhodium.
- the cell element is then rinsed and filled with phosphoric acid solution in the usual manner.
- An electrolytic hygrometer cell having at least one electrode composed of rhodium.
- An electrolytic hygrometer cell having at least one electrode whose active portion contains rhodium.
- An electrolytic hygrometer cell having a pair of spaced electrodes, said electrodes consisting of substantially pure rhodium.
- An electrolytic hygrometer capable of operation in a hydrogen atmosphere Without substantial hydrogen recombination comprising: an inner jacket of insulating material having a passage therethrough; a pair of spaced electrodes supported in said jacket and having at least a portion thereof adjoining said passage; 21 hygroscopic substance bridging the space between said electrodes; means to apply a potential between said electrodes; at least one of said electrodes being composed of rhodium.
- An electrolytic hygrometer capable of operation in a hydrogen atmosphere Without substantial hydrogen recombination comprising: an inner jacket of insulating material having a passage therethrough; a pair of spaced electrodes supported in said jacket and having at least a portion thereof adjoining said passage; a hygroscopic substance bridging the space between said electrodes; means to apply a potential between said electrodes; said electrodes composed of rhodium.
Description
Dec. 14, 1965 J. w. REEDS, JR 3,223,609
HYGROMETER Filed Oct. 50, 1961 s Sheets-Sheet 1 A IO FIG. 1
NTo JOHN w. REEDs Dec. 14, 1965 J. w. REEDS, JR
HYGROMETER 3 Sheets-Sheet 2 Filed Oct. 30, 1961 mmv NJ wm mm llrll INVENTOR.
J 1 S WG D E L w H N H 0 V Y B ATTORNEY Dec. 14, 1965 J. w. REEDS, JR 3,223,609
HYGROMETER Filed Oct. 30, 1961 5 Sheets-Sheet 3 RHODIUM P NG SOLUTIO [72 g so INVENTOR.
BY JOHN W. REEDS, JR.
ATTORNEY United States Patent 3,223,609 HYGROMETER John W. Reeds, In, La Habra, Califi, assignor to Beckman Instruments, Inc, a corporation of California Filed Oct. 30, 1961, Ser. No. 148,442 9 Claims. (Cl. 204-495) This invention relates to hygrometers and more particularly relates to an improved electrolytic hygrometer cell.
Electrolytic hygrometers have been widely used for determining the moisture content of fluid streams in industrial processes in which the presence of even minute percentages of moisture is of great significance. This type of hygrometer has numerous advantages over other moisture determining devices, particularly when used in conjunction with continuous process streams, as it is quite selective to water, has a rapid speed of response, and is completely quantitative over wide ranges of moisture concentration, thereby eliminating the need for frequent calibration and standard samples.
Electrolytic hygrometers depend for their operation on the relationship between the amount of water present in a hygroscopic substance and the amount of current necessary to electrolyze it. The active elements of the most commonly available hygrometers comprise a pair of helical platinum conductors partially embedded in a supporting tubular jacket, the interior of which is coated with a hygroscopic substance which bridges the spaces between adjacent turns of the helixes. The gas or vapor to be tested is passed over the hygroscopic substance which absorbs the moisture present in the gas or vapor and becomes conductive. An electric current is then passed between the adjacent turns of the two platinum conductors and the water is electrolyzed to hydrogen and oxygen. The amount of current necessary to completely electrolyze the water is, of course, a measure of the moisture content of the fluid beihg tested.
Although the cells described are satisfactory for most applications, their useful life is short, averaging only about 40,000 part per million-hours when used at a sample flow rate of 100 cubic centimeters/minute. Thus, in a process stream in which the moisture content is 1,000 parts per million, the average cell will fail in 40 hours. This short lifetime results in great inconvenience in all applications, and in those applications where it is desired to continuously monitor a process stream whose moisture content is highly critical, that is, in the very applications wherein the cells are most effective, the usefulness of the electrolytic hygrometer is severely limited.
It has been noted that after a period of use a black deposit, apparently platinum or a platinum compound, appears between the platinum electrodes. The formation of this deposit occurs most rapidly at the entrance and exit portions of the cell, but takes place to some degree throughout its entire length. The deposit eventually builds up to a point where it forms a metallic bridge between adjacent turns of the electrodes and being electrically conductive, causes a short circuit between them, resulting in cell failure.
It has also been found that the presently available cells must be modified for use with gas streams comprising more than 50 percent hydrogen and that even when modified, cell accuracy is extremely sensitive to changes in gas condition. It is believed that the inaccuracy of the cell when used with a hydrogen stream is due primarily to recombination of the oxygen liberated by the electrolysis with the hydrogen stream, thus creating additional water which is again electrolyzed, possibly several times. The recombination of hydrogen and oxygen is apparently catalyzed by the presence of platinum or platinum compounds in the cell, both the electrodes themselves and the de- 3,223,609 Patented Dec. 14, 1965 posits between them having an eflect on the rate of recombination.
According to the present invention, it has now been found that an electrolitic hygrometer cell may be provided that has an extremely long life expectancy and which may be used with equal facility on streams containing any percentage of hydrogen. The important advantage of long life expectancy may be obtained by providing the cell with at least one rhodium electrode which serves as the anode when the cell is operatively connected in an appropriate electrical circuit. For use on hydrogen streams, the anode should be rhodium and the cathode should be a conductor which does not catalyze the recombination of hydrogen and oxygen. Both electrodes may be rhodium for this application.
It is therefore a primary object of the present invention to provide an electrolytic hygrometer cell which has a life expectancy far in excess of any cell heretofore known.
It is another object of the present invention to provide an electrolytic hygrometer cell which may be used on a fluid stream regardless of its hydrogen content.
It is a further object of the present invention to provide an electrolytic hygrometer cell whose active element has at least one rhodium electrode.
It is a still further object of the present invention to provide a rhodium electrode for an electrolytic hygrometer cell.
These and further objects and advantages of the invention will become more apparent upon reference to the following specification and claims and appended drawings wherein:
FIG. 1 is a sectional view of one type of active element of an electrolytic hygrometer cell incorporating the teachings of the present invention;
FIG. 2 is a view partly in section of a portion of an electrolytic hygrometer cell according to the present invention;
FIG. 3 is a view partly in section of an electrolytic hygrometer cell according to the present invention;
FIG. 4 is a sectional view of another form of active element of an electrolytic hygrometer cell incorporating the teachings of the present invention;
FIG. 5 is a schematic showing of an electrical circuit used to form an electrolytic hygrometer cell in accordance with one aspect of the present invention; and
FIG. 6 is a sectional view of a portion of another form of active element of an electrolytic hygrometer cell incorporating the teachings of the present invention.
Referring now to FIG. 1, there is shown for use in electrolytic hygrometers an active element, generally indicated at 10, which comprises a pair of helically wound, substantially pure rhodium electrodes 12 and 14 partially embedded in a jacket 16 of a suitable insulating material, "for example, a thermoplastic resin such as polychlorotrifluoroethylene. If desired, this jacket may be constructed of glass or another suitable material. The unembedded or active portions of the rhodium electrodes 12 and 14 make up a portion of the surface of an interior annular passageway 18 extending through the thermoplastic jacket 16. The electrodes 12 and 14 terminate in a pair of conductors 20 and 22 which protrude outwardly from the end of the thermoplastic jacket 16 so that the electrodes may be connected into a suitable electrical circuit. The annular surface of the interior passageway 18 through the jacket 16 is coated with a thin film of a suitable hygroscopic substance, for example, phosphorus pentoxide, so that each segment of insulating material separating alternate active portions of the rhodium electrodes 12 and 14 is bridged by a material which may become conductive.
The active element just described is preferably made in accordance with the teachings of U.S. application Serial No. 134,506, filed August 28, 1961, by Douglas B. Gardner and assigned to the assignee of the present application. Briefly, this element is made by spacewinding the electrodes 12 and 14 on a stainless steel mandrel, extruding the jacket 16 over the mandrel and the electrodes, removing the mandrel, peeling the jacket back to expose the ends of the electrodes, and passing a slurry of phosphoric acid through the annular passageway previously occupied by the mandrel to form the bridging film of phosphorus pentoxide.
The use of rhodium as the electrode material vastly extends the useful life of an electrolytic cell. Tests indicate that the life expectancy of an electrolytic cell utilizing rhodium electrodes is well over 500,000 part per millionhours in contrast with the aforementioned 40,000 part per million-hours for cells utilizing platinum electrodes. It has been found that when substantially pure rhodium electrodes are used, the inter-electrode deposits previously referred to are completely or nearly completely eliminated.
It has also been discovered that the incorporation of rhodium electrodes into an electrolytic cell enables it to be used to accurately measure the moisture content of gas or vapor streams, regardless of their hydrogen content. The rhodium electrodes themselves do not appear to catalyze the recombination of liberated oxygen and hydrogen as do platinum electrodes when they are employed in a similar environment and, moreover, no interelectrode deposits are formed which might act as a catalyst for this reaction. As a result, the recombination, if any, that takes place is insignificant, and the only water electrolyzed is that which enters the cell in the gas or vapor stream.
In order to improve cell performance markedly, the electrodes need not be of substantially pure rhodium but may be composed of an alloy of rhodium. These alloys, however, do not extend the life of a cell as greatly as does substantially pure rhodium. For example, an alloy of 60 percent platinum and 40 percent rhodium was found to increase the life of a cell by approximately a factor of over a cell having platinum electrodes. This example is, of course, strictly illustrative, as any alloy having a rhodium content not substantially less than 40 percent will be useful, for example, alloys of rhodium and iridium or osmium as well as other alloys of platinum and rhodium will appreciably increase cell life.
Furthermore, it has been found that only the electrode which serves as the anode in the electrolysis need be of rhodium to prevent the deposition of inter-electrode deposits. The use of a pair of rhodium electrodes is, however, preferred because the use of a single electrode requires that one terminal of the cell be always positive, thus decreasing its convenience and adaptability in use; In addition, the presence of the platinum electrode would somewhat increase the recombination rate of liberated oxygen and hydrogen if the cell were used on a hydrogen stream, thus making it less attractive for this use. The presence of platinum in a rhodium-platinum alloy would also have this effect on a hydrogen stream.
Referring now to FIGS. 2 and 3, there is shown a complete electrolytic cell incorporating an active element similar to that shown in FIG. 1. As may be seen in FIG. 2, the conductors 20 and 22 protrude from the end of the element 10 and are bent back over the jacket at an angle of 180 and held snugly against the jacket by means of a sleeve 26, preferably of polytetrafiuoroethylene. The extremeties of the rhodium conductors 20 and 22 are joined to a pair of copper conductors 28 and 30, in any suitable fashion, for example, by means of solder 32. This junction is protected by a thermofitting plastic tube 34 which, together with the polytetrafluor oethylene sleeve 26, prevents movement of the somewhat delicate rhodium conductors 20 and 22 and thereby protects them from being broken during the assembly and use of the cell.
' The complete cell is assembled as shown in FIG. 3.
In the construction of this cell, a suitable length of active element 10 is coiled in any desired manner, for instance,
' it may be heated and wrapped around a mandrel of suitable diameter. When the element cools, it will remain in the shape of a helix and may be easily introduced into a stainless steel casing 36. The casing 36 is provided with a pair of ports 38 and 40 which are sealed by a pair of insulating members 42 and 44 made of any suitable material. As shown, these members take the form of commercial metal to glass hermetic feed-through termirials. The insulators 42 and 44 are provided with annular passageways 46 and 48 for the passage of conductors 28 and 30 therethrough from the active element in the interior of the casing 36 to the point where they may be connected into an appropriate indicating circuit.
After the conductors 28 and 30 have been drawn through the passageways 46 and 48, these passageways are sealed closed by any suitable means, for example by solder 50.
After the active element 10 has been inserted into the casing 36 and the conductors 28 and 30 drawn through the insulating members 42 and 44, one end of the casing 36 is closed by means of a steel washer 52 that rests upon a shoulder 54 provided on the inner surface of the casing 36. A polytetrafiuoroethylene plug 56 having a slightly tapered interior passageway is then inserted into the end and seated on the washer 52 and the seal is then completed by passing a polytetrafluoroethylene sleeve 58 over the end of the active element 10 and forcing it against the taper of the passageway in the plug 56 until it is firmly seated. The interior of the casing 36 is then filled with a suitable potting compound 60, care being taken that none of the potting compound blocks the open end of the element 10. The resulting structure is a durable, long-lasting electrolytic hygrometer cell that can be used with equal effect on streams having high or low hydrogen contents.
Referring now to FIG. 4 there is shown another type of active element that may incorporate the teachings of the present invention. This type element is made by wrapping a pair of rhodium electrodes separated by a pair of copper spacer windings around a mandrel and extruding a suitable jacket e.g., of polytetrafluoroethylene over the wires and the mandrel. The mandrel is then removed and the copper spacer windings etched away. The surface of the annular passageway formed by the removal of the mandrel is then coated with a thin film of a suitable hygroscopic substance. This type element can be incorporated into the cells shown in FIG. 3 in place of the element 10. The use of rhodium in place of platinum for the electrodes in this type of cell element also increases its life in the same fashion as previously described.
Since it is only necessary that the active portions of the anode electrode be of rhodium, long-lasting cells may be produced by plating the active or unembedded portions of one or both platinum electrodes with a film of rhodium. A circuit suitable for such a process is shown in FIG. 5. In this figure, a suitable cell 70 is shown from which extends a pair of conductors 72 and 74 through a pair of insulating members 76 and 78. The active element of the cell in this figure is constructed with platinum electrodes and may be formed in the manner shown in FIGS. 1 or 4 or in any other suitable fashion.
The conductors 72 and 74 are connected in a series circuit with a suitable source of voltage 80, a variable resistor 82, an ammeter 84, and a switch 86. A commercial rhodium plating solution is then introduced into the active element through a conduit 88 and the switch 86 closed. The resulting voltage across the two cell electrodes causes the electrode connected as the cathode to be plated with rhodium. The cell element is then rinsed and filled with phosphoric acid solution in the usual manner.
FIG. 6 shows a portion of an active element produced by the process of FIG. 5. The active element used in the plating process was one similar to that shown in FIG. 4. The active elements comprise a suitable jacket 90 in which are embedded a pair of of platinum electrodes 92 and 94. After the electroplating, a film of rhodium, shown in greatly exaggerated fashion at 96, covers the active or exposed, portions of the electrode 94. These exposed portions are the only electrically active portions of the electrodes, as the remaining portions of the electrodes are completely embedded in insulating material. After the rhodium is plated onto the active portion of the electrode 94, a film of a hygroscopic substance 98 is coated on the entire surface, as described previously. When this cell is operated with the positive electrolyzing voltage applied to the rhodium plated electrode, the cell has an extremely long life compared with any presently known. Cells made in this fashion, however, have the same disadvantages as previously mentioned for cells having only one rhodium electrode.
From the foregoing, it can be seen that an electrolytic hygrometer cell is provided that is far more useful and long-lasting than any others heretofore proposed. These salutary results are achieved by using at least one electrode having an active surface containing rhodium. This rhodium-containing surface can be obtained by making either or both of the electrodes of substantially pure rhodium, an alloy containing rhodium, or by plating rhodium on the active surface of a platinum electrode.
The invention may be embodied in other specific forms not departing from the spirit or essential characteristics thereof, other forms of electrolytic hygrometer cells being equally improved by the use of the present invention as those described herein. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come Within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
I claim:
1. An electrolytic hygrometer cell having at least one electrode composed of rhodium.
2. An electrolytic hygrometer cell having at least one electrode whose active portion contains rhodium.
3. An electrolytic hygrometer cell having at least one electrode consisting of substantially pure rhodium.
4. An electrolytic hygrometer cell having a pair of spaced electrodes, said electrodes consisting of substantially pure rhodium.
5. In an electrolytic hygrometer, the improvement of providing at least one electrode with an active portion containing rhodium.
6. An electrolytic hygrometer capable of operation in a hydrogen atmosphere Without substantial hydrogen recombination comprising: an inner jacket of insulating material having a passage therethrough; a pair of spaced electrodes supported in said jacket and having at least a portion thereof adjoining said passage; 21 hygroscopic substance bridging the space between said electrodes; means to apply a potential between said electrodes; at least one of said electrodes being composed of rhodium.
7. An electrolytic hygrometer capable of operation in a hydrogen atmosphere without substantial hydrogen recombination comprising: an inner jacket of insulating material having a passage therethrough; a pair of spaced electrodes supported in said jacket and having at least a portion thereof adjoining said passage; a hygroscopic substance bridging the space between said electrodes; means to apply a potential between said electrodes; at least one of said electrodes having an active portion composed of rhodium.
8. An electrolytic hygrometer capable of operation in a hydrogen atmosphere Without substantial hydrogen recombination comprising: an inner jacket of insulating material having a passage therethrough; a pair of spaced electrodes supported in said jacket and having at least a portion thereof adjoining said passage; a hygroscopic substance bridging the space between said electrodes; means to apply a potential between said electrodes; said electrodes composed of rhodium.
9. An electrolytic hygrometer capable of operation in a hydrogen atmosphere without substantial hydrogen recombination comprising: an inner jacket of insulating material having a passage therethrough; a pair of spaced electrodes supported in said jacket and having at least a portion thereof adjoining said passage; a hygroscopic substance bridging the space between said electrodes; means to apply a potential between said electrodes; said electrodes consisting of substantially pure rhodium.
References Cited by the Examiner UNITED STATES PATENTS 2,719,797 l0/ 1955 Rosenblatt 204290 2,830,945 4/1958 Keidel 204 2,863,729 12/1958 McDuffie et al. 23204 2,934,693 4/1960 Reinecke et a1. 204195 3,021,482 2/1962 Estes 204195 3,023,085 2/ 1962 McBride 23204 FOREIGN PATENTS 759,288 10/1956 Great Britain.
OTHER REFERENCES Babor et al.: General College Chemistry, 1940, pages 146 and 147.
The Condensed Chemical Dictionary, Reinhold Publishing Corporation, August 1961, page 810.
JOHN H. MACK, Primary Examiner.
JOHN R. SPECK, Examiner.
MURRAY TILLMAN, T. TUNG, Assistant Examiners.
Claims (1)
1. AN ELECTROLYTIC HYGROMETER CELL HAVING AT LEAST ONE ELECTRODE COMPOSED OF RHODIUM.
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US148442A US3223609A (en) | 1961-10-30 | 1961-10-30 | Hygrometer |
GB30901/62A GB1018192A (en) | 1961-10-30 | 1962-08-13 | Electrolytic hygrometer cell |
FR910654A FR1334757A (en) | 1961-10-30 | 1962-09-27 | Hygrometer |
DEB69345A DE1191136B (en) | 1961-10-30 | 1962-10-23 | Hygrometer cell |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US148442A US3223609A (en) | 1961-10-30 | 1961-10-30 | Hygrometer |
Publications (1)
Publication Number | Publication Date |
---|---|
US3223609A true US3223609A (en) | 1965-12-14 |
Family
ID=22525790
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US148442A Expired - Lifetime US3223609A (en) | 1961-10-30 | 1961-10-30 | Hygrometer |
Country Status (3)
Country | Link |
---|---|
US (1) | US3223609A (en) |
DE (1) | DE1191136B (en) |
GB (1) | GB1018192A (en) |
Cited By (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3325378A (en) * | 1964-04-10 | 1967-06-13 | Beckman Instruments Inc | Electrochemical method and apparatus for measuring hydrogen content |
US3449231A (en) * | 1966-06-22 | 1969-06-10 | Beckman Instruments Inc | Oxygen sensor with rhodium cathode |
US3450619A (en) * | 1966-05-24 | 1969-06-17 | Cambridge Instr Co Inc | Oxygen detector |
US3954590A (en) * | 1972-08-18 | 1976-05-04 | E. I. Du Pont De Nemours And Company | Iridium thin ribbon electrodes for electrochemical cells |
US4076596A (en) * | 1976-10-07 | 1978-02-28 | Leeds & Northrup Company | Apparatus for electrolytically determining a species in a fluid and method of use |
US4140990A (en) * | 1976-02-18 | 1979-02-20 | U.S. Philips Corporation | Probe for selectively detecting vapors, water vapor in particular |
DE2924694A1 (en) * | 1978-06-19 | 1980-01-03 | Nat Res Dev | ELECTROCHEMICAL MEASURING SYSTEM AND METHOD USING THIS ELECTROCHEMICAL MEASURING SYSTEM |
WO1981001423A1 (en) * | 1979-11-09 | 1981-05-28 | J Savery | Method of and apparatus for active electrochemical water and similar environmental contaminant elimination in semiconductor and other electronic and electrical devices and the like |
US4449396A (en) * | 1982-03-01 | 1984-05-22 | Carrier Corporation | Probe for measuring electrical conductance |
DE3504498A1 (en) * | 1985-02-09 | 1986-08-14 | Drägerwerk AG, 2400 Lübeck | GAS SENSOR WITH SEVERAL SENSOR ELEMENTS |
WO1989007264A1 (en) * | 1988-02-08 | 1989-08-10 | Rosemount Inc. | Thin film moisture sensing elements and process for the manufacture thereof |
US4990236A (en) * | 1988-02-08 | 1991-02-05 | Rosemount Inc. | Thin film moisture sensing element |
WO1992006371A1 (en) * | 1990-10-03 | 1992-04-16 | Meeco, Incorporated | Epoxy-less low-level moisture measurement system and method |
US5589085A (en) * | 1995-08-04 | 1996-12-31 | Meeco, Incorporated | Process of manufacturing a detecting unit for an electrolytic cell with thin film electrodes |
US20020040598A1 (en) * | 2000-10-10 | 2002-04-11 | Ngk Spark Plug Co., Ltd. | Humidity sensor |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2064126A (en) * | 1979-11-22 | 1981-06-10 | Philips Electronic Associated | Method of making humidity sensors |
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US2719797A (en) * | 1950-05-23 | 1955-10-04 | Baker & Co Inc | Platinizing tantalum |
GB759288A (en) * | 1954-02-15 | 1956-10-17 | Johnson Matthey Co Ltd | Improvements in and relating to electrodes |
US2830945A (en) * | 1955-05-03 | 1958-04-15 | Du Pont | Apparatus for water determination |
US2863729A (en) * | 1953-02-27 | 1958-12-09 | Harold F Mcduffie | Combination of hydrogen and oxygen |
US2934693A (en) * | 1957-09-09 | 1960-04-26 | Phillips Petroleum Co | Water analyzer |
US3021482A (en) * | 1962-02-13 | estes | ||
US3023085A (en) * | 1960-03-30 | 1962-02-27 | John P Mcbride | Method of combining hydrogen and oxygen |
-
1961
- 1961-10-30 US US148442A patent/US3223609A/en not_active Expired - Lifetime
-
1962
- 1962-08-13 GB GB30901/62A patent/GB1018192A/en not_active Expired
- 1962-10-23 DE DEB69345A patent/DE1191136B/en active Pending
Patent Citations (7)
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US3021482A (en) * | 1962-02-13 | estes | ||
US2719797A (en) * | 1950-05-23 | 1955-10-04 | Baker & Co Inc | Platinizing tantalum |
US2863729A (en) * | 1953-02-27 | 1958-12-09 | Harold F Mcduffie | Combination of hydrogen and oxygen |
GB759288A (en) * | 1954-02-15 | 1956-10-17 | Johnson Matthey Co Ltd | Improvements in and relating to electrodes |
US2830945A (en) * | 1955-05-03 | 1958-04-15 | Du Pont | Apparatus for water determination |
US2934693A (en) * | 1957-09-09 | 1960-04-26 | Phillips Petroleum Co | Water analyzer |
US3023085A (en) * | 1960-03-30 | 1962-02-27 | John P Mcbride | Method of combining hydrogen and oxygen |
Cited By (19)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3325378A (en) * | 1964-04-10 | 1967-06-13 | Beckman Instruments Inc | Electrochemical method and apparatus for measuring hydrogen content |
US3450619A (en) * | 1966-05-24 | 1969-06-17 | Cambridge Instr Co Inc | Oxygen detector |
US3449231A (en) * | 1966-06-22 | 1969-06-10 | Beckman Instruments Inc | Oxygen sensor with rhodium cathode |
US3954590A (en) * | 1972-08-18 | 1976-05-04 | E. I. Du Pont De Nemours And Company | Iridium thin ribbon electrodes for electrochemical cells |
US4140990A (en) * | 1976-02-18 | 1979-02-20 | U.S. Philips Corporation | Probe for selectively detecting vapors, water vapor in particular |
US4076596A (en) * | 1976-10-07 | 1978-02-28 | Leeds & Northrup Company | Apparatus for electrolytically determining a species in a fluid and method of use |
DE2924694A1 (en) * | 1978-06-19 | 1980-01-03 | Nat Res Dev | ELECTROCHEMICAL MEASURING SYSTEM AND METHOD USING THIS ELECTROCHEMICAL MEASURING SYSTEM |
US4280885A (en) * | 1979-11-09 | 1981-07-28 | Savery James W | Method of and apparatus for active electro-chemical water and similar environmental contaminant elimination in semi-conductor and other electronic and electrical devices and the like |
WO1981001423A1 (en) * | 1979-11-09 | 1981-05-28 | J Savery | Method of and apparatus for active electrochemical water and similar environmental contaminant elimination in semiconductor and other electronic and electrical devices and the like |
DE3050032C2 (en) * | 1979-11-09 | 1987-06-11 | James Savery | Getter device for electrochemically removing water |
US4449396A (en) * | 1982-03-01 | 1984-05-22 | Carrier Corporation | Probe for measuring electrical conductance |
DE3504498A1 (en) * | 1985-02-09 | 1986-08-14 | Drägerwerk AG, 2400 Lübeck | GAS SENSOR WITH SEVERAL SENSOR ELEMENTS |
WO1989007264A1 (en) * | 1988-02-08 | 1989-08-10 | Rosemount Inc. | Thin film moisture sensing elements and process for the manufacture thereof |
US4990236A (en) * | 1988-02-08 | 1991-02-05 | Rosemount Inc. | Thin film moisture sensing element |
WO1992006371A1 (en) * | 1990-10-03 | 1992-04-16 | Meeco, Incorporated | Epoxy-less low-level moisture measurement system and method |
US5225065A (en) * | 1990-10-03 | 1993-07-06 | Meeco, Inc. | Epoxy-less low-level moisture measurement system and method |
US5589085A (en) * | 1995-08-04 | 1996-12-31 | Meeco, Incorporated | Process of manufacturing a detecting unit for an electrolytic cell with thin film electrodes |
US20020040598A1 (en) * | 2000-10-10 | 2002-04-11 | Ngk Spark Plug Co., Ltd. | Humidity sensor |
US6883371B2 (en) * | 2000-10-10 | 2005-04-26 | Ngk Spark Plug Co., Ltd. | Humidity sensor |
Also Published As
Publication number | Publication date |
---|---|
GB1018192A (en) | 1966-01-26 |
DE1191136B (en) | 1965-04-15 |
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