Static drop mercury electrode

• US 4,260,467 A
• Filed: 01/26/1978
• Issued: 04/07/1981
• Est. Priority Date: 01/26/1978
• Status: Expired due to Term

• Current Assignee: Princeton Applied Research Corporation
• Original Assignee: Princeton Applied Research Corporation
• Inventors: Smith, John L., Whitlock, Bruce N.
• Primary Examiner(s): Tung, T.
• Application Number:
  US05/872,506
• Time in Patent Office: 1,167 Days
• Field of Search: 204/195 H, 324/31
• US Class Current: 204/413
• CPC Class Codes: G01N 27/34 Dropping-mercury electrodes
• CPC Class Codes: G01N 27/48 using polarography, i.e. measuring changes in current under a slowly-varying voltage

Abstract

Mercury flow from a reservoir of mercury to a mercury drop capillary extending vertically downward from the reservoir is governed by selective engagement of a sealing surface immersed in the mercury reservoir with a valve seat also immersed in the mercury reservoir to allow for controlled formation of mercury drops at the lower end of the capillary which drops, after formation, are held non-growing or static. The capillary is removable from the housing and when so removed the sealing surface engages the housing of the reservoir to prevent loss of mercury from the reservoir.

Claims

1. A static mercury drop electrode comprising:

a housing forming a reservoir for liquid mercury;

a dropping mercury capillary having first and second ends and forming a capillary passage therebetween with said capillary passage terminating in a downward direction at said second end; and

valve means for selective air-purging passage of mercury from said reservoir to said first end of said capillary to form static mercury drops at said second end of said capillary, said valve means including a valve seat positioned in said reservoir beneath the surface of said mercury at said first end of said capillary, sealing means for forming a sealing surface, and control means for selectively controlling the relative position of said sealing surface and said valve seat between an open position with said sealing surface disengaged from said first valve seat and in contact with mercury in said reservoir, and a closed position with said sealing surface engaged with said first valve seat to prevent flow of said mercury from said reservoir to said capillary passage.

2. The static mercury drop electrode according to claim 1 wherein said first end of said capillary forms said first valve seat.

3. The static mercury drop electrode according to claim 2 wherein said first end of said capillary is located above the lowermost portion of said reservoir, causing said first end to be surrounded by mercury.

4. The static mercury drop electrode according to claim 1 including means for providing electrical coupling between mercury in said capillary passage and mercury in said reservoir.

5. The static mercury drop electrode according to claim 1 wherein said sealing means comprises a plunger with said sealing surface formed on one end thereof, said plunger being mounted in said housing for movement by said control means co-linear with the axis of said capillary.

6. The static mercury drop electrode according to claim 5 wherein said control means includes a spring biasing said sealing surface of said plunger into said one of said positions and further includes a solenoid operable on said plunger to bias said sealing surface into the other of said positions.

7. The static mercury drop electrode according to claim 6 wherein said housing forms a sealed reservoir and said housing further includes means for providing access to said reservoir to allow maintenance of a constant pressure on said mercury at said first end of said capillary.

8. The static mercury drop electrode according to claim 1 wherein said housing forms a second valve seat adjacent said capillary and said sealing surface is adapted to engage said second valve seat upon removal of said capillary passage extending means from said reservoir.

20. The static mercury drop electrode according to claims 1 or 9 wherein said sealing means comprises a plunger with said sealing surface formed on one end thereof, said plunger being mounted in said housing for movement of said sealing surface by said control means in a direction which intersects a plane defined by the surface of said valve seat.

9. A static mercury drop electrode comprising:

a housing forming a reservoir for mercury;

a dropping mercury capillary extending from said housing, said capillary having first and second ends and forming a capillary passage from said reservoir at said first end to said second end with said capillary passage terminating in a downward direction at said second end and said passage being of sufficiently small diameter to form hanging mercury drops at said second end,

an air-impervious valve means for forming a selectively operable air-purging passage from said reservoir to said first end of said capillary to allow controlled formation of static mercury drops at said second end of said capillary, said valve means including a first valve seat formed by said first end of said capillary and positioned in said reservoir beneath the surface of said murcury, sealing means for forming a sealing surface, and control means for selectively moving said sealing surface between an open position with said sealing surface disengaged from said first valve seat and in contact with said mercury in said reservoir and a closed position with said sealing surface engaged with said first valve seat to prevent passage of said mercury in said reservoir to said capillary.

10. The static mercury drop electrode according to claim 9 wherein said first end of said capillary is located above the lowermost portion of said reservoir causing said first end to be surrounded by mercury in said open condition.

11. The static mercury drop electrode according to claim 9 including means for electrically connecting mercury in said capillary passage with mercury in said reservoir.

12. The static mercury drop electrode according to claim 11 wherein said sealing means comprises a plunger with said sealing surface formed on one portion thereof, said plunger being mounted in said housing for movement by said control means co-linear with the axis of said capillary.

13. The static mercury drop electrode according to claim 12 wherein said control means includes a spring to bias said sealing surface of said plunger into said closed position and further includes a solenoid operable on said plunger to pull said sealing surface into said open position.

14. The static mercury drop electrode according to claim 13 wherein said housing has an aperture to receive said capillary and said housing has a second valve seat positioned to engage said sealing surface upon removal of said extending means from said reservoir and to prevent passage of mercury through said aperture.

15. A static mercury drop electrode comprising:

a housing for holding liquid mercury;

a hanging drop capillary extending vertically downward from said housing with the upper end of said capillary extending into said housing to form a first flat surface and said capillary being of sufficiently fine bore to allow formation of hanging mercury drops at the lower end of said capillary; and

a plunger moveably mounted in said housing and having a lower second flat surface immersed in said mercury paralled to said first flat surface, said second flat surface of said plunger selectively moveable in a direction to intersect the plane defined by said first flat surface and engageable with said first flat surface to allow selective formation of static mercury drops at the lower end of said capillary.

16. The static mercury drop electrode according to claim 15 wherein said upper end of said capillary is located above the lowermost portion of said reservoir causing said first end to be completely surrounded by mercury when said lower surface of said plunger is disengaged therefrom.

17. The static mercury drop electrode according to claim 16 including means for electrically connecting mercury in said capillary with mercury in said housing.

18. The static mercury drop electrode according to claim 17 including a spring to bias said lower surface of said plunger against the upper surface of said capillary, and further comprising a solenoid operable on said plunger to pull said lower surface of said plunger away from said upper end of said capillary.

19. The static mercury drop electrode according to claim 18 wherein said housing has an opening to receive said capillary and said housing has a surface surrounding said opening and said plunger is biased by said spring to engage said surface and close said opening upon removal of said capillary from said reservoir.