US3838971A

US3838971A - Electrolytic alcohol detection

Info

Publication number: US3838971A
Application number: US00357155A
Authority: US
Inventors: C Albertson
Original assignee: Borg Warner Corp
Current assignee: ALCOHOL COUNTERMEASURE SYSTEMS CORP; Borg Warner Corp
Priority date: 1973-05-04
Filing date: 1973-05-04
Publication date: 1974-10-01
Anticipated expiration: 1991-10-01

Abstract

An electrolytic cell is formed of a pair of lead electrodes and an aqueous solution of sulfuric acid or phosphoric acid. The electrolyte is subjected to an environment comprising a gas such as human breath to be tested for the presence or concentration of alcoholic vapor. The electrical conductivity of the cell is measured and compared to its conductivity when subjected to ambient air or a gas containing a predetermined concentration of alcoholic vapor.

Description

United States Patent 11 1 1111 3,838,971

Albertson Oct. 1, 1974 [5 ELECTROLYTIC ALCOHOL DETECTION 3,613,665 10 1971 Gorsuch 23 254 R 3,622,278 11/1971 Elzinga 23/232 R [75] Inventor Clarence Album, V1113 Park, 3,764,270 10/1973 Collier et a1. 23/255 E 3,7s5,774 1 1974 Murphy 23/254 E [73] Assignee: Borg-Warner Corporation, Chicago,

[1] Primary ExaminerR. E. Serwin Filed: May 1973 Attorney, Agent, or Firm-Donald W. Banner [2]] Appl. No.: 357,155 [57] ABSTRACT An electrolytic cell is formed of a pair of lead elec- [52] mg 3 23 232 2 30 B 23 254 5 trodes and an aqueous solution of sulfuric acid or 23 255 5 12 /2 C, 204 195 B phosphoric acid. The electrolyte is subjected to an en- [51 Int. Cl. 60111 33/16, GOln 27/06 vironmem comprising a gas Such as human breath to [58] Field f S h 23/230 3 232 E, 254 E, be tested for the presence or concentration of alco- 23/255 5; 123 2 204/195 3; 324 71 holic vapor. The electrical conductivity of the cell is measured and compared to its conductivity when sub- [56] References Cited jected to ambient air or a gas containing a predeter- UNITED STATES PATENTS mined concentration of alcoholic vapor.

3,600,134 8/1971 Noller 23/232 E 7 Claims, 1 Drawing Figure g1 g1 g1 51 ,ma

BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates to electrolytic alcohol detection, and more particularly, to a method of and means for detecting the presence or determining the concentration of alcholic vapor in a gas such as human breath.

As used herein, the terms alcohol and alcoholic refer to ethyl alcohol or ethanol, the intoxicating agent in fermented beverages and in beverages distilled from products of fermentation. The term breath refers to the gaseous products of human expiration; that is, the

gases released or expelled from the lungs by way of the mouth and/or nose. The terms intoxicating and intoxication refer to the temporary diminution of mental and physical control or capability which results from the ingestion of alcoholic beverages in amounts and at a rate or frequency beyond the capacity of the metabolism.

As is well known, the degree of intoxication of an individual who has ingested alcoholic beverages is directly related to the degree of concentration of alcohol in his blood and can be determined by extracting and testing a sample of blood. However, such procedure requires substantial training, experience and care, it is frequently inconvenient, it is often distasteful to the subject, and under certain circumstances it may be objectionable on legal grounds. On the other hand, it is generally accepted that the concentration of alcoholic vapor in the breath is directly related to the content of alcohol in the blood, and a number of systems have been devised for detecting alcoholic vapor in the breath or for measuring its concentration. Such systems are in general free of the objections raised against blood sampling and testing. One example of such a system is described and illustrated in patent application Ser. No. 136,921, filed Apr. 23, 1971 in the names of D. W. Collier et al. and assigned to the assignee of the present invention.

The present invention makes use of the fact that alcohol is readily absorbed by an aqueous solution of sulfu- 5 ric acid or phosphoric acid. Such a solution also serves as an excellent electrolyte. If an electric potential is applied to an electrolytic cell situated in an alcohol-free environment, conductivity of the cell can be determined by measuring the electric current flowing through the cell. If the cell is then subjected to an alcoholic environment, whereby alcohol is absorbed by the electrolyte, and the same potential applied, the absorbed alcohol will be oxidized and the conductivity of the cell increased, as indicated by greater current flow.

The electrolytic cell in accordance with the invention comprises a pair of lead electrodes and a preferred electrolyte of 40% sulfuric acid by weight. Such a cell can be incorporated in a device of simple construction which may be quite small and light and thus readily portable. It is also relatively durable; lead electrodes are well-known to have long life in storage batteries containing sulfuric acid electrolyte.

While the invention is intended primarily for use in breath-testing apparatus, it also finds application in analyzing other gases for alcoholic vapor content.

THE DRAWING The FIGURE is a schematic representation of an electrolytic alcohol detection device constructed and adapted to be operated in accordance with the present invention.

THE PREFERRED EMBODIMENT Referring to the drawing, there are shown means forming an electric circuit 10 and a gas-receiving chamber 12. The gas'receiving chamber 12 is enclosed by any suitable gas-impervious material, preferably light in weight, and includes a testing portion 16, a gas inlet 18 and a gas outlet 20. The inlet 18 and outlet 20 are in open communication with the testing portion 16 and are shown in fragmentary form. They may be fitted, respectively, with a breathing mask (not shown) adapted to cover the nose and mouth of a subject to be tested, and any suitable gas discharge means (also not shown).

The electric circuit 10 comprises electrically conductive elements 21 interconnecting, in series, a suitable source 22 of constant dc, electric potential, means responsive to changes in electric current, shown in the drawing as a milliammeter 24, and an electrolytic cell 28 situated within the testing portion 16 of the gasreceiving chamber 12 and there supported by any suitable means (not shown). Electric circuit 10 may also include a switch 26 for selectively opening and closing the circuit. The source 22 is selected to provide a constant potential preferably in the range of 2.0 to 3.0 volts.

The electrolytic cell comprises a pair of

electrodes

30 and 32, each formed of lead and arranged to hold an electrolyte therebetween, by means of surface tension, in a position to be in contact with a gas received in the chamber 12.

More particularly, the electrode 30 comprises a loop, ring or annulus of a size to receive and hold a drop of electrolyte, and the electrode 32 comprises a terminus positioned to be in electrical contact with the drop of electrolyte at a location spaced from and within the annulus. An annulus having an inside diameter of approximately 1/8 inch is suitable for the purposes of the invention. However, it will be recognized that the

electrodes

30 and 32 may be of various shapes and dimensions, so long as the electrolyte is permitted substantial contact with the gas received in the: chamber 12. Referring to the drawing, it will be noted that the electrolyte will be substantially surrounded by any gas present in the testing portion 16. The

electrodes

30 and 32 are preferably connected in the circuit 10 in a manner such that the electrode 30 will serve as the anode and the electrode 32 as the cathode.

OPERATION As previously mentioned, the preferred electrolyte is a solution of approximately 40 percent by weight of sulfuric acid in water, although a solution of phosphoric acid can be substituted satisfactorily.

The apparatus is quite simple to operate. A drop of electrolyte is first placed in the annulus of the electrode 30, and thereby in electrical contact with both

electrodes

30 and 32, where it is held by surface tension. The electric circuit 10 is then completed, as by closing the switch 26. At this point the environment of the electrolytic cell 28; that is, the contents of the gasreceiving chamber 12, comprises ambient air, which may serve as a control gas.

When the current flow achieves a steady state, as indicated by the rnilliammeter 24, the conductivity of the cell 28 is measured by noting the value of the current, and the switch 26 is opened.

The ambient air within the gas-receiving chamber 12 is now replaced by a gas to be tested for the presence of alcoholic vapor. This may be done, for example, by a subject individual exhaling into the gas inlet 18 for a period of approximately 4 to 6 seconds. Continuous exhalation throughout a period of such duration will ensure not only that the ambient air will be completely replaced within the chamber 12 by the gas to be tested, but also that the test gas will consist of deep-lung breath. Simultaneously with or shortly before exhalation into the gas-receiving chamber 12, the switch 26 is again closed. The conductivity is again measured by noting the value of the current, and the two measurements compared.

If there has been an increase in current equal to or greater than a predetermined minimum increase, the presence of alcoholic vapor in the test gas is indicated. The predetermined minimum increase is established by means of a gas having a known minimum concentration of alcoholic vapor.

Instead of ambient air, breath known to have no alcoholic vapor content can be used as the control gas and may be preferable since its moisture or water vapor content will more closely approximate that of the breath to be tested.

By way of example, if a potential of 2.25 volts is applied to the electrolytic cell 28, the rnilliammeter 24 might indicate 0.18 milliamperes in the case of ambient air, 0.19 milliamperes in the case of non-alcoholic breath, and 0.21 milliamperes in the case of breath containing a concentration of A of 1 percent alcoholic vapor by volume.

Similarly, with an applied potential of 2.5 volts the respective measurements might be 0.28 milliamperes in air, 0.30 milliamperes in non-alcoholic breath and 0.32 milliamperes in breath containing the stated concentration of alcoholic vapor. On the average, the current through the electrolytic cell has been observed to increase approximately 7 percent in non-alcoholic breath and 14 percent in the presence of alcohol in the stated concentration.

If the approximate concentration of alcoholic vapor in breath is to be determined, initial conductivity of the electrolytic cell 28 is first established in the manner heretofore described, using either ambient air or nonalcoholic breath as a first control gas. When a first measurement of the electrical conductivity of the cell has been effected by observing the steady-state reading of the rnilliammeter 24, the first control gas is replaced by a second control gas having a predetermined concentration of alcoholic vapor and, after 4 to 6 seconds, a second measurement is taken. The second control gas is then replaced by the first control gas and the cell 28 is pre-electrolyzed; that is, current is permitted to continue to flow until any residual alcohol has been removed from the electrolyte, as indicated when the milliammeter reading returns to a value approximately equal to the value observed in the first measurement. The first control gas is now replaced by the gas to be tested, and after 4 to 6 seconds the conductivity of the cell is measured a third time by observing the new milliammeter reading. The second and third measurements are then compared to determine the concentration of the alcoholic vapor in the test gas.

More particularly, the percentage increases of the second and third measurements over the first measurement are computed. The ratio of the percentage increase of the second measurement to the percentage increase of the third measurement will be approximately equal to the ratio of the concentration of alcoholic vapor in the second control gas to the concentration of alcoholic vapor in the test gas.

While the procedures described heretofore call for the test gas to be introduced into the gas-receiving chamber 12 after the control gas or gases, it will be apparent that the order can be reversed and remain within the purview of the invention. ln any case, however, the electrolyte must be free of absorbed alcohol before a control or test gas is introduced.

The apparatus and procedure described heretofore will provide satisfactory results in the normal range of room temperatures and humidity. However, in the presence of low humidity, water may be evaporated from the electrolyte, thereby raising the concentration of acid substantially above the preferred 40 percent by weight. Conversely, high humidity may dilute the electrolyte. Also, current flow across the electrolytic cell 28 in the presence of absorbed alcohol may vary with changes in temperature.

It should be pointed out that the rnilliammeter 24 may be replaced by other well-known means responsive to changes in current, or it may be included in addition to such means. The latter might include, for example, an actuator arranged to light an indicator lamp or to open (or fail to close) the ignition circuit of an automobile when a predetermined current or increase in current is achieved.

While the invention has been described in connection with a specific embodiment thereof, it is to be understood that this is by way of illustration and not by way of limitation; and the scope of the appended claims should be construed as broadly as the prior art will permit.

I claim:

1. A method of detecting the presence of alcoholic vapor in a gas, using an electrolytic cell which includes a pair of electrodes formed of lead, and an electrolyte comprising an aqueous solution of an acid selected from the group consisting of sulfuric acid and phosphoric acid, the method comprising the steps of subjecting and electrolyte to an environment comprising a control gas free of alcoholic vapor, measuring the electrical conductivity of the electrolytic cell, replacing the control gas with a gas to be tested for the presence of alcoholic vapor, again measuring the electrical conductivity of the electrolytic cell, and comparing the two measurements.

2. A method of determining the presence and concentration of alcoholic vapor in a gas, using an electrolytic cell which includes a pair of electrodes formed of lead, and an electrolyte comprising an aqueous solution of an acid selected from the group consisting of sulfuric acid and phosphoric acid, the method comprising the steps of subjecting the electrolyte to an environment comprising a first control gas free of alcoholic vapor, effecting a first measurement of the electrical conductivity of the electrolytic cell, replacing the first control gas with a second control gas having a predetermined concentration of alcoholic vapor, effecting a second measurement of the electrical conductivity of the electrolytic cell, replacing the second control gas with the first control gas, adjusting the conductivity of the electrolylic cell to a value approximately equal to the value indicated by the first measurement, replacing the first control gas with a gas having an unknown concentration of alcoholic vapor if any, effecting a third measurement of the electrical conductivity of the electrolytic cell, and comparing the second and third measurements.

3. The method as defined in claim 2, wherein each of the measurements of electrical conductivity is carried out by applying an electric potential of predetermined constant magnitude to the electrodes, and determining the magnitude of the electric current flowing through the cell.

4. The method as defined in claim 3 wherein the predetermined constant magnitude of the electric potential applied to the electrodes is in the range of 2.0 volts to 3.0 volts.

5. The method as defined in claim 2, wherein the electrolyte comprises a solution of approximately 40% by weight of sulfuric acid in water.

6. An electrolytic alcohol detection device comprising means forming a chamber for receiving control gases and gases to be tested for the presence of alcoholic vapor, the chamber having an inlet and an outlet, and means forming an electric circuit including an electrolytic cell disposed in the chamber, a source of constant dc, electric potential, means responsive to changes in electric current, and means electrically connecting the cell, the potential source and the currentresponsive means in series, the electrolytic cell comprising a pair of electrodes each formed of lead, the electrodes being formed to hold by surface tension an electrolyte therebetween in a position to be in contact with a gas received in the chamber, the electrolyte comprising an aqueous solution of an acid selected from the group consisting of sulfuric acid and phosphoric acid.

7. An electrolytic alcohol detection device as defined in claim 6, wherein one of the electrodes comprises an annulus of a size to receive and hold a drop of the electrolyte, and the other electrode comprises a terminus positioned to be in electrical contact with the drop of electrolyte at a location spaced from and within the an- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIUN Patent No. 5 9 3 ,97 Dated @013. 1, 197

Clarence E. Albertson lnventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column LP, line 51, I Claim 1, line 7, "and electrolyte" should read the electrolyte Column 6, line 6, I

Claim 6, line 7, after "dc" cancel the Signed and sealed this 17th day of December 1974.

(SEAL) Attest:

McCOY Ifi. GIBUN R. Ca MARSHALL DA NN At-testlng Officer Commissioner of Patents FORM PO-1050 (10-69) USCOMM-DC 60376-PG9 U.S. GO VERNNENT PRINTING OFFICE: 93 o

Claims

1. A METHOD OF DETECTING THE PRESENCE OF ALCOHOLIC VAPOR IN A GAS, USING AN ELECTROLYTIC CELL WHICH INCLUDES A PAIR OF ELECTRODES FORMED OF LEAD, AND AN ELECTROLYTE COMPRISING AN AQUEOUS SOLUTION OF AN ACID SELECTED FROM THE GROUP CONSISTING OF SULFURIC ACID AND PHOPHORIC ACID, THE METHOD COMPRISING THE STEPS OF SUBJECTING AND ELECTROLYTE TO AN ENVIROMENT COMPRISING A CONTROL GAS FREE OF ALCOHOLIC VAPOR, MEASURING THE ELECTRIC CAL CONDUCTIVITY OF THE ELECTROLYTIC CELL, REPLACING THE CONTROL

6. An electrolytic alcohol detection device comprising means forming a chamber for receiving control gases and gases to be tested for the presence of alcoholic vapor, the chamber having an inlet and an outlet, and means forming an electric circuit including an electrolytic cell disposed in the chamber, a source of constant dc, electric potential, means responsive to changes in electric current, and means electrically connecting the cell, the potential source and the current-responsive means in series, the electrolytic cell comprising a pair of electrodes each formed of lead, the electrodes being formed to hold by surface tension an electrolyte therebetween in a position to be in contact with a gas received in the chamber, the electrolyte comprising an aqueous solution of an acid selected from the group consisting of sulfuric acid and phosphoric acid.

7. An electrolytic alcohol detection device as defined in claim 6, wherein one of the electrodes comprises an annulus of a size to receive and hold a drop of the electrolyte, and the other electrode comprises a terminus positioned to be in electrical contact with the drop of electrolyte at a location spaced from and within the annulus.