US2849391A - Mercury capillary assembly - Google Patents

Description

MERCURY CAPILLARY ASSEMBLY Filed Oct. 15, 1956 INVENTOR m4;- Kfl/FL MD/SC/f,

ATTORNEY fired States Patent 2,849,391 MERCURY CAPILLARY ASSEMBLY Rolf Karl Ladisch, Lansdowne, Pa. Application October 15, 1956, Serial No. 616,060

4 Claims. 01. 204-195 The general object of the present invention is to provide an improved mercury capillary assembly.

In a prior art patent, No. 2,728,721, issued to myself and S. Knesbach December 27, 1955, there is described and claimed a novel polarographic electrode assembly of the dropping mercury type for maintaining the rate of flow and the drop size of the mercury discharged by the assembly very nearly constant. In this invention, the assembly is maintained in service by mercury being supplied from an inner reservoir to an outer reservoir through the action of a capillary side arm connected to the upper part of the inner reservoir, as is fully described in said patent. Due to the small cross-sectional area of the inner reservoir in relation to the cross-sectional area of the outer reservoir, only a relatively small portion of the overall charge of mercury can be stored and utilized for keeping the assembly in service during polarographic analyses. The construction also sets up a pronounced meniscus of the mercury at the tip of the capillary side arm between the inside wall of the outer reservoir and the outside wall of the inner reservoir, thus rendering the assembly sensitive to mechanical vibrations. Furthermore, the capillary side arm is bent at the place where it is connected to the inner reservoir and may trap and hold some of the mercury in the bend, thereby cancelling the desired valve action of the capillary side arm until the mercury is removed from the bend of the side arm.

One of the objects of the present invention is to construct a dropping mercury assembly in such a manner that the greater portion of the overall charge of mercury can be utilized for supplying the mercury to operate the assembly. A further object is to minimize the dimensions of the assembly and yet to maintain the assembly operating in polarographic testing over a period of about two weeks with a single filling. A further object is to simplify the construction. A further object is to construct a capillary mercury assembly incorporating a capillary valve which contacts the upper surface of the mercury driving head at a place where the surface of the mercury is substantially plane and free of a meniscus. A further object is to employ a capillary valve having over its entire length a substantially straight bore. Other objects will be apparent from the following description of the preferred embodiment of the invention shown in the accompanying drawing forming a part of this specification. Said drawing is a longitudinal section through the assembly.

Referring particularly to the drawing, a tube 1, preferably of polymethylmethacrylate resin, is connected at its lower end to a capillary 2 by means of Tygon tubing 3. At its upper end, tube 1 merges with a lower reservoir 4, preferably of polymethylmethacrylate and preferably having cylindrical form. Reservoir 4 is open to the air through vent 5. Placed on reservoir 4 is an upper reservoir 6, preferably of methylmethacrylate and preferably also having cylindrical form. Reservoir 6 has a glued-in-bottom 7, preferably of polymethylmethacrylate,

2,849,391 Patented Aug. 26, 1958 a threaded plug member 8 screwed into its top, and a rubber or other collapsible bulb 9 fitted on member 8. Plug member 8 has a central port or air passage 14. Rubber ring 10 between member 8 and reservoir 6 seals the reservoir 6 olf from the atmosphere. A tube 11 is tightly fitted into the bottom 7 of reservoir 6 and extends downwardly to near the bottom of reservoir 4. A capillary 12, preferably of polymethylmethacrylate and glued into the bottom 7 of reservoir 6, extends upwardly to near the ceiling of reservoir 6 as well as downwardly into reservoir 4, with its lower end being spaced above the lower opening of tube 11. The lower end of capillary 12 is drawn to a point or tip 13. Diameters of oneeighth of an inch for the bore in tube 11 and 500 microns for the bore in capillary 12, have been found satisfactory for operating the assembly.

To operate the described assembly, member 8 including the collapsible bulb 9 is unscrewed from the assembly. Instrument mercury M of high purity is poured into reservoir 6, from where it flows through tube 11 into reservoir 4. A suflicient amount of mercury M is introduced to fill reservoir 4 to near the height of vent 5. Member 8 including collapsible bulb 9, together with rubber ring 10, are screwed back onto reservoir 6 to seal the interior of reservoir 6 011 from the atmosphere. Then collapsible bulb 9 is squeezed. This forces part of the air from reservoir 6 out through tube 11 and capillary 12, this air escaping in bubbles through the mercury in reservoir 4 and leaving the assembly through vent 5. Then collapsible bulb 9 is relieved. Thereby, a partial vacuum is created in reservoir 6, and mercury flows from reservoir 4 up through tube 11 into reservoir 6. concomitantly, the level of the mercury in reservoir 4 falls below the tip 13 of capillary 12. When this occurs, air from above the pool of mercury M in reservoir 4 flows through capillary 12 into the upper part of reservoir 6. This lowers the vacuum in reservoir 6, and mercury flows down through tube 11 into reservoir 4, until the level of the mercury pool rises to touch tip 13 and hence seal capillary 12. The system is then balanced or stable. But any withdrawal of mercury from capillary 2 causes the pool of mercury to sink below tip 13, which acts as a valve, with the same action as described above. After a long period of operation, the supply of mercury in reservoir 6 will be exhausted.

. Then the mercury may be replenished as described.

This assembly may be used in polarographic analyses employing dropping mercury electrodes or streaming mercury electrodes. In general, it will be useful for maintaining a very nearly constant mercury overhead in applications where a flow of mercury from a capillary under a driving head of mercury is involved.

What I claim is:

l. A dropping mercury capillary assembly comprising, in combination, a body having two separate mercury reservoirs, one directly above the other, both reservoirs being of substantially the same lateral dimensions; the upper reservoir having a top wall, and a bottom wall separating it from the l wer reservoir; a collapsible elastomeric bulb secured to said top Wall and being open to the upper reservoir so that, when it is collapsed and then released, it will create a partial vacuum in the upper part of the upper reservoir; the lower reservoir having in its upper portion a vent to the atmosphere and also having a bottom wall; a capillary that is straight throughout its length extending from the upper part of the upper reservoir through the bottom wall of the upper reservoir down to a level somewhat above the bottom wall of the lower reservoir, the lower end of said capillary being drawn down to a point or tip; a mercury-conducting tube extending from the bottom of the upper reservoir nearly to the bottom wall of the lower reservoir, the lower end of said tube being below the lower pointed end of said capillary; a tube coupled to the bottom wall of the lower reservoir to conduct mercury therefrom; and a second capillary coupled to the lower end of the lastnamcd tube toform drops of mercury;

2. The invention defined in claim 1, wherein there is a removable plug member-sealed into the top-wall-of theupper reservoir; said plug" member having anair passage extendingtherethrough fronrtop to bottom, said bulb being fitted 'onsaid plug member-fsaid'plug member, when removed, giving accessto; the; interior of the body forthe introduction of' mercur'y therein.

3. The iHVCDlZlQHdCfiIlGd'ill-Claim 2 wherein theremovable plug member is 'screwed into the top wall of the upper reservoir; at; the centen thereof; the mercuryconducting tube' is located near" the inner peripheries of-the upper and-lowerreservoirs;;the capillary that extends through the bottomw-allof the; upper reservoir is in thecenter of said-bottom-wallj-and' the tube that is coupled to the bottom wall of thelower reservoir is directly belowthe pointed lower end ofthe last-named capillary.

4; A dropping mercuryt capillary assembly comprising, in combination, a body having two separate mercury reservoirs, one directly above the other and both reservoirsbeing of substantiallythe samelateral dimensions; the-upper reservoir having atop wall'and a bottom wall separating it from thelower reservoir; a collapsible elastomericbulb securedto'saidtopwall and-open to the upper reservoir so that, when it is collapsed and then released, itwillcreatea-partial vacuum in the upper part of the upper reservoir thereby to draw mercury up into the upper reservoir; the lower reservoir having in its upper portion a vent to the atmosphere and also having a bottom wall; a mercury-conducting tube extending from the bottom of the upper reservoir nearly to the bottom wall of the lower reservoir; a capillary that is straight throughoutits length extending from the upper part of the upper reservoir through the bottom wall of the upper reservoir down to a level somewhat above the bottom wall of the lower reservoir, but higher than the lower end of said mercury-conducting tube; the lower end of said capillary beingdrawn'down to a point or tip; a tube coupled to the bottom wall of the lower reservoir to conduct mercury therefrom; a second capillary coupled to the lower end of the last-named tube to form drops of mercury at its lower end; there being a supply of mercury in said reservoirs sufiicient to-form a shallow pool of mercury on the bottom wall'of the lower reservoir with the'mercury presenting a substantially plane upper surface of relatively very large area compared to said point or tip which contacts it.

2,728,721 Ladisch et a1. Dec. 27, 1955

Claims (1)

1. A DROPPING MERCURY CAPILLARY ASSEMBLY COMPRISING, IN COMBINATION, A BODY HAVING TWO SEPARATE MERCURY RESERVOIRS, ONE DIRECTLY ABOVE THE OTHER, BOTH RESERVOIRS BEING OF SUBSTANTIALLY THE SAME LATERIAL DIMENSIONS; THE UPPER RESERVOIR HAVING A TOP WALL, AND A BOTTOM WALL SEPARATING IT FROM THE LOWE RESERVOIR; A COLLASIBLE ELASTOMERIC BULB SECURED TO SAID TOP WALL AND BEING OPEN TO THE UPPER RESERVOIR SO THAT, WHEN IT IS COLLAPSED AND THEN RELEASED, IT WILL CREATE A PARTIAL VACUUM IN THE UPPER PART OF THE UPPER RESERVOIR; THE LOWER RESERVOIR HAVING IN ITS UPPER PORTION A VENT TO THE ATMOSPHERE AND ALSO HAVING A BOTTOM WALL; A CAPILLARY THAT IS STRAIGHT THROUGHOUT ITS LENGTH EXTENDING FROM THE UPPER PART OF THE UPPER RESERVOIR THROUGH THE BOTTOM WALL OF THE UPPER RESERVOIR DOWN TO A LEVEL SOMEWHAT ABOVE THE BOTTOM WALL OF THE LOWER RESERVOIR, THE LOWER END OF SAID CAPILLARY BEING DRAWN DOWN TO A POINT OR TIP; A MERCURY-CONDUCTING TUBE EXTENDING FROM THE BOTTOM OF THE UPPER RESERVOIR NEARLY TO THE BOTTOM WALL OF THE LOWER RESERVOIR, THE LOWER END OF SAID TUBE BEING BELOW THE LOWER POINTED END OF SAID CAPILLARY; A TUBE COUPLED TO THE BOTTOM WALL OF THE LOWER RESERVOIR TO CONDUCT MERCURY THEREFROM; AND A SECOND CAPILLARY COUPLED TO THE LOWER END OF THE LASTNAMED TUBE TO FORM DROPS OF MERCURY.

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