US4315753A — Electrochemical apparatus for simultaneously moni…

Claim 1

Independent Claim 199 words

An apparatus for simultaneously monitoring the presence of first and second members of a family of oxygen-containing gases in a sample of gas, said apparatus comprising: (a) a first indicating means for generating a first indicating signal in response to the presence of the first member in the sample while forming a first gas mixture; (b) means for receiving said first gas mixture from said first indicating means and for converting all of the second member present in said first gas mixture into the first member to form a second gas mixture; (c) a second indicating means for receiving said second gas mixture from said converting means and for generating a second indicating signal in response to the presence of first member in said second gas mixture; and (d) circuit means for receiving said first and second indicating signals from said first and second indicating means and for respectively generating first and second output signals in response to said first and second indicating signals, said first output signal being representative of the amount of the first member present in the sample and said second output signal being representative of the amount of the second member present in the sample.

Claim 2

Independent Claim 199 words

An apparatus for simultaneously monitoring the presence of first and second members of a family of oxygen-containing gases in a sample of gas, said apparatus comprising: (a) a first indicating means for generating a first indicating signal in response to the presence of the first member in the sample while forming a first gas mixture; (b) means for receiving said first gas mixture from said first indicating means and for converting all of the second member present in said first gas mixture into the first member to form a second gas mixture; (c) a second indicating means for receiving said second gas mixture from said converting means and for generating a second indicating signal in response to the presence of first member in said second gas mixture; and (d) circuit means for receiving said first and second indicating signals from said first and second indicating means and for respectively generating first and second output signals in response to said first and second indicating signals, said first output signal being representative of the amount of the first member present in the sample and said second output signal being representative of the amount of the second member present in the sample.

Claim 3

Dependent Claim 25 words

Apparatus as set forth in claim 1, wherein said first and second indicating means respectively include first and second electrodes mounted within an electrochemical cell.

Claim 4

Dependent Claim 120 words

Apparatus as set forth in claim 2, wherein said electrochemical cell includes an electrolyte in contact with said first electrode such that at least a portion of the first member present in the sample is electroreduced at said first indicating means to generate said first indicating signal in the form of an electrical signal while producing said first gas mixture, said first gas mixture producing said first gas mixture, said first gas mixture comprising electroreduction products, second member and unreduced first member, said electrolyte also contacting said second electrode such that the first member present in said second gas mixture is electroreduced at said second indicating means to generate said second indicating signal in the form of an electrical current.

Claim 5

Dependent Claim 38 words

Apparatus as set forth in claim 3, wherein said converting means includes an oxidizing means for converting all of the second member present in said first gas mixture into the first member to form said second gas mixture.

Claim 6

Dependent Claim 15 words

Apparatus as set forth in claim 4, wherein said electrolyte is an aqueous acid electrolyte.

Claim 7

Dependent Claim 33 words

Apparatus as set forth in claim 3, wherein said electrochemical cell also includes a reference electrode and an auxiliary electrode which form, together with said first and second electrode, a four electrode potentiostat.

Claim 8

Dependent Claim 20 words

Apparatus as set forth in claim 6, wherein said reference electrode comprises a glass element in contact with said electrolyte.

Claim 9

Dependent Claim 59 words

Apparatus as set forth in claim 3, wherein said circuit means includes a compensating means for removing from said second indicating signal the signal characteristics resulting from the presence in said first gas mixture of both unreduced first member and second member produced as a consequence of the electroreduction of the first member occuring in said first indicating means.

Claim 10

Dependent Claim 30 words

Apparatus as set forth in claim 8, wherein said compensating means subtracts a fractional amount of said first indicating signal from said second indicating signal to produce a difference signal.

Claim 11

Dependent Claim 45 words

Apparatus as set forth in claim 9, wherein said circuit means additionally includes a first amplifier means for amplifying said first indicating signal to generate said first output signal and a second amplifier means for amplifying said difference signal to generate said second output signal.

Claim 12

Dependent Claim 23 words

Apparatus as set forth in claims 1 or 2, wherein the first member is nitrogen dioxide and the second member is nitric oxide.

Claim 13

Dependent Claim 29 words

Apparatus as set forth in claims 3, 4, 5, 6, 7, 8, 9 or 10, wherein the first member is nitrogen dioxide and the second member is nitric oxide.

Claim 14

Dependent Claim 15 words

Apparatus as set forth in claim 12, wherein said aqueous acid electrolyte includes sulfuric acid.

Claim 15

Dependent Claim 20 words

Apparatus as set forth in claim 13, wherein said aqueous acid electrolyte comprises a mixture of sulfuric and sulfamic acids.

Claim 16

Dependent Claim 48 words

Apparatus as set forth in claim 12, wherein said first and second electrodes both include a hydrophilic porous supporting membrane having a first layer of gold coated thereon and a second layer of silver overlying said gold layer such that said second layer of silver contacts said electrolyte.

Claim 17

Dependent Claim 17 words

Apparatus as set forth in claim 15, wherein said hydrophilic porous supporting membrane is formed from Teflon.

Claim 18

Dependent Claim 17 words

Apparatus as set forth in claim 12, wherein said first and second electrodes operate at cathodic potentials.

Claim 19

Dependent Claim 26 words

Apparatus as set forth in claim 17, wherein the potentials of said first and second electrodes are held at -0.24 volts relative to said reference electrode.

Claim 20

Dependent Claim 74 words

An electrode means for contacting both a sample of gas and an aqueous electrolyte to electrochemically reduce nitrogen dioxide present in the sample, said electrode means including a hydrophilic porous supporting membrane having a first surface which contacts the aqueous electrolyte and a second surface which contacts the sample of gas, said first surface having a first layer of gold coated thereon and a second layer of silver overlying said first layer of gold.

Claim 21

Dependent Claim 74 words

An electrode means for contacting both a sample of gas and an aqueous electrolyte to electrochemically reduce nitrogen dioxide present in the sample, said electrode means including a hydrophilic porous supporting membrane having a first surface which contacts the aqueous electrolyte and a second surface which contacts the sample of gas, said first surface having a first layer of gold coated thereon and a second layer of silver overlying said first layer of gold.

Claim 22

Dependent Claim 46 words

An electrode means as set forth in claim 19, including a glass tube having an opening at one end thereof and said hydrophilic porous supporting membrane mounted across said opening, whereby said second surface is exposed to a sample of gas enclosed within said glass tube.

Claim 23

Dependent Claim 33 words

An electrode means as set forth in claim 20, wherein an electrical contact lead is connected to said first layer of gold to remove current generated during the electrochemical reduction of nitrogen dioxide.

Claim 24

Dependent Claim 149 words

Circuit means for providing first and second output signals in an apparatus in order to monitor the presence of first and second constitutents of a sample of gas, which apparatus includes electrochemical means for generating a first indicating signal having a characteristic resulting from the presence of the first constitutent in the sample and a second indicating signal having a characteristic resulting from the combined presence of the first and second constitutents in the sample, said circuit means comprising: (a) first amplifier means for amplifying the first indicating signal to provide said first output signal; (b) compensating means for subtracting a fractional amount of the first indicating signal from the second indicating signal to produce a difference signal having a characteristic resulting only from the presence of the second constituent in the sample; and (c) second amplifier means for amplifying said difference signal to provide said second output signal.

Claim 25

Dependent Claim 149 words

Circuit means for providing first and second output signals in an apparatus in order to monitor the presence of first and second constitutents of a sample of gas, which apparatus includes electrochemical means for generating a first indicating signal having a characteristic resulting from the presence of the first constitutent in the sample and a second indicating signal having a characteristic resulting from the combined presence of the first and second constitutents in the sample, said circuit means comprising: (a) first amplifier means for amplifying the first indicating signal to provide said first output signal; (b) compensating means for subtracting a fractional amount of the first indicating signal from the second indicating signal to produce a difference signal having a characteristic resulting only from the presence of the second constituent in the sample; and (c) second amplifier means for amplifying said difference signal to provide said second output signal.

Claim 26

Dependent Claim 32 words

Circuit means as set forth in claim 22, wherein said compensating means is connected between the output side of said first amplifier means and the input side of said second amplifier means.

Claim 27

Dependent Claim 15 words

Circuit means as set forth in claim 23, wherein said compensating means includes a potentiometer.

Claim 28

Dependent Claim 22 words

Circuit means as set forth in claim 22, including a power supply means for supplying an operating voltage to said circuit means.

Claim 29

Dependent Claim 63 words

Circuit means as set forth in claim 25, wherein said power supply means includes a low power shut-off means for interrupting the supply of said operating voltage from said power supply means to said circuit means and for preventing said circuit means from receiving the first and second indicating signals whenever the absolute value of said operating voltage falls below a predetermined level.

Claim 30

Dependent Claim 36 words

Circuit means as set forth in claim 26, wherein said low power shut-off means includes at least one comparator means for comparing the value of said operating voltage with a reference voltage having said predetermined level.

Claim 31

Dependent Claim 18 words

Circuit means as set forth in claim 25, wherein said power supply means includes an energy storage means.

Claim 32

Dependent Claim 21 words

Circuit means as set forth in claim 22, wherein said first and second amplifier means each includes a current booster means.

Claim 33

Independent Claim 150 words

A method for simultaneously monitoring the presence of first and second members of a family of oxygen-containing gases in a sample of gas, said method comprising the steps of: (a) electroreducing at least a portion of the first member in the sample to derive a first electrical signal while forming a first gas mixture comprising electroreduction products, unreduced first member and second member; (b) oxidizing the second member in said first gas mixture to convert all of the second member present in said first gas mixture to the first member to form a second gas mixture; (c) electroreducing at least a portion of the first member and in said second gas mixture to derive a second electrical signal; and (d) electronically processing said first and second electrical signals to generate first and second output signals respectively representative of the amount of the first and second members present in the sample.

Claim 34

Independent Claim 150 words

A method for simultaneously monitoring the presence of first and second members of a family of oxygen-containing gases in a sample of gas, said method comprising the steps of: (a) electroreducing at least a portion of the first member in the sample to derive a first electrical signal while forming a first gas mixture comprising electroreduction products, unreduced first member and second member; (b) oxidizing the second member in said first gas mixture to convert all of the second member present in said first gas mixture to the first member to form a second gas mixture; (c) electroreducing at least a portion of the first member and in said second gas mixture to derive a second electrical signal; and (d) electronically processing said first and second electrical signals to generate first and second output signals respectively representative of the amount of the first and second members present in the sample.

Claim 35

Dependent Claim 22 words

A method as set forth in claim 30, wherein the first member is nitrogen dioxide and the second member is nitric oxide.

Claim 36

Dependent Claim 34 words

A method as set forth in claim 31, wherein nitrogen dioxide is electroreduced by contacting the nitrogen dioxide with an electrode structure which includes a metallic silver portion immersed in an aqueous acid electrolyte.

Claim 37

Dependent Claim 24 words

A method as set forth in claim 32, wherein said electrode structure is held at a cathodic potential relative to a predetermined reference level.

Claim 38

Dependent Claim 26 words

A method as set forth in claim 33, wherein said electrode structure is held at a potential of -0.24 volts relative to said predetermined reference level.

Claim 39

Dependent Claim 25 words

A method as set forth in claim 30, wherein the second member is oxidized by contacting the second member with Cr 2 O 3 .

Claim 40

Independent Claim 80 words

A method for manufacturing an electrode capable of electroreducing nitrogen dioxide, said method comprising the steps of: (a) stretching a hydrophilic porous membrane over an electrode support structure; (b) applying a gold resinate over the surface of said hydrophilic porous membrane; (c) heat curing the resinate until a coating of gold is formed on said hydrophilic porous membrane; and (d) electroplating said hydrophilic porous membrane to form a coating of silver on the exposed surface of said coating of gold.

Claim 41

Independent Claim 80 words

A method for manufacturing an electrode capable of electroreducing nitrogen dioxide, said method comprising the steps of: (a) stretching a hydrophilic porous membrane over an electrode support structure; (b) applying a gold resinate over the surface of said hydrophilic porous membrane; (c) heat curing the resinate until a coating of gold is formed on said hydrophilic porous membrane; and (d) electroplating said hydrophilic porous membrane to form a coating of silver on the exposed surface of said coating of gold.

Claim 42

Dependent Claim 47 words

A method as set forth in claim 36, including the step of conditioning the coating of gold by immersing the hydrophilic porous membrane having said coating of gold formed thereon in a 1 M solution of HCl0 3 and applying a current to said coating of gold.

Claim 43

Dependent Claim 35 words

A method as set forth in claim 37, wherein said current applied to said coating of gold is a square wave current alternating between -50 mA and +50 mA at a frequency of 0.1 Hz.

Claim 44

Dependent Claim 43 words

A method as set forth in claim 38, wherein said square wave current is applied to said coating of gold for at least eight hours and nitrogen gas is blown over the hydrophilic porous membrane while said square wave current is being applied.

Claim 45

Dependent Claim 33 words

A method as set forth in claim 36, wherein said steps of applying and heat curing said gold resinate are repeated to form a multi-coating layer of gold on said hydrophilic porous membrane.

Claim 46

Independent Claim 22 words

A method as set forth in claims 36 or 40, wherein said gold resinate comprises 28% gold suspended in an organic matrix.

Claim 47

Dependent Claim 43 words

A method as set forth in claim 36, wherein said electroplating is accomplished by immersing the goldcoated hydrophilic porous membrane in a 0.1 M AgNO 3 /1 M HNO 3 solution and potentiostating said coating of gold at 0.0 volts for 3 minutes.

Claim 48

Dependent Claim 136 words

An electrochemical means for detecting predetermined constituents in a sample of gas, said electrochemical means including: (a) a cell structure enclosing a supporting electrolyte; (b) an indicator electrode means mounted in said cell structure for generating an electrical signal in response to the presence of a predetermined atmospheric constituent, said indicator electrode means comprising a hydrophilic porous supporting membrane having a first surface which contacts said supporting electrolyte and a second surface which contacts the sample of gas, said first surface having a first layer of gold coated thereon and a second layer of silver overlying said first layer of gold; and (c) a reference electrode means mounted in said cell structure for maintaining a reference potential relative to said indicating electrode means, said reference electrode comprising a glass element in contact with said supporting electrolyte.

Claim 49

Dependent Claim 136 words

An electrochemical means for detecting predetermined constituents in a sample of gas, said electrochemical means including: (a) a cell structure enclosing a supporting electrolyte; (b) an indicator electrode means mounted in said cell structure for generating an electrical signal in response to the presence of a predetermined atmospheric constituent, said indicator electrode means comprising a hydrophilic porous supporting membrane having a first surface which contacts said supporting electrolyte and a second surface which contacts the sample of gas, said first surface having a first layer of gold coated thereon and a second layer of silver overlying said first layer of gold; and (c) a reference electrode means mounted in said cell structure for maintaining a reference potential relative to said indicating electrode means, said reference electrode comprising a glass element in contact with said supporting electrolyte.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1985-02-15	1985-08-17	1986-02-16	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1989-02-15	1989-08-17	1990-02-16	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1993-02-15	1993-08-17	1994-02-16	$7700.00	Window Closed / Lapsed

Electrochemical apparatus for simultaneously monitoring two gases

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