US895159A - Method of producing amalgams or alloys. - Google Patents

Description

No. 895,159. PATENTED AUG. 4, 1908.

c. F. CARRIER, Jn,' -Q METHOD OF PRODUCING AMALGAMS 0R ALLOYS. v

7 APPLICATION FILED JAN. 11, 19 1,. V

v 2 SH BETSSHEBT 2.

C OURTLAND F. CARRIER. IR., OF ELMIRA, NERV YORK.

METHOD OF PRODUCING AMALGAMS R ALLOYS.

This invention is a method or producing amalgams or alloys by the decomposition of electrolytes in presence of a fluid metal cathode, the object of the invention being to se cure a higher efficiency of operation than has heretofore been possible, and to attain other advantages as hereinafter set forth.

The invention will be described by reference to the preparation of alkali metal amalgams by electrolysis of chlorid solutions with a mercury cathode; it is not however restricted to such use, but is applicable to the electrolysis of other aqueous solutions, as

well as to the decomposition of molten electrolytes in presence of a fluid cathode of lead or other metal.

In the commercial methods of preparing amalgams of the alkali metals for the production of hydroxid solutions it is usual to electrolyze an alkali chlorid solution in presence of an insoluble anode and a cathode of mercury, the latter in the form of a thin-layer beneath the anode; as the mercury becomes charged with sodium it is intermittently or continuously conveyed into the )resence of As this water to oxidize the alkali meta method has been heretofore carried out in practice it possesses several disadvantages, as follows: l

(a) The amalgam becomes constantly richer in sodium as it flows from the inlet to the outlet. With the increase in the percentage of sodium in the amalgam, the electrode potential also increases. The result is that the fall of potential is greater near the outlet for the amalgam than near the inlet, thus more of the current flows through the electrolyte at the point farthest from where the amalgam, floating on the surface of the mercury, is to be removed from the action of the electrolyte. l t will therefore be seen that more than half of the deposited sodium has to traverse the greater portion of the distance from the inlet to the outlet. been partially overcome by the use of a series of long narrow anode and cathode compartments in which the mercury flows across the shorter dimension, but. the multiplication in V Specification of Letters Patent. Application filed Ianuary 11, 190i. Serial No.'351,881.' I

This has breaking up of the patches, and to reduce the Patented Aug. '4, 1908.

the number of compartments necessary greatly complicates the apparatus. Under similar conditlons, the longer the amalgam is.

in contact with the electrolyte, the greater will be the loss of sodium by re-solution.

(b) In many of the cells heretofore proposed for the pre aration of alkali metal amalgam, the ama gam has to flow out beneath a solid artition which has to extend to a suflicient epth below the surface of the mercury to form a seal between the compartments. The disadvantage of removing from the bottom a material which collects on the surface is self evident.

(0) Perhaps the greatest difficult rests in the tendency of the mercury to thic en, even with a small percentage of sodium. The sodium collects at or near the surface of the mercury forming a solid amalgam which floats on the main body of the mercury. This crust is retarded at every oint where it touches a solid body, so that t 1e velocity of flow tends to be greater near the center than near the sides. The result is thata rich amalgam will be formed near the sides, which will not be carried away as rapidly as the poorer amalgam nearer the center where the mercury current is stronger. amalgam is the slower it tends to flow. loss of sodium b v lyte increases with the duration of the exposure and in this case the richest amalgam tends to remain the longest in contact with the electrolyte. The crust also thickens to some extent at oints which are not adjacent to the sides an such portions do not flow as rapidly as the oorer portions of the amalgain, except w en the mercury current is very strong. The variation in the r'ate of flow at the various points on the surface of the lncrcury tends to distort the patches of amalgam crust floating on the surface of the mercury, breaking them up into smaller patches. At every crack or break in these patches, local electrolytic action set up, whichmeans'loss of sodium. By noting the point at which visible evolution of gas takes place, it may be observed that the local action takes place at the edges of the watches and not on t 16 flat upper surface. t is de- The sirable therefore to eliminate as far as possi- The richer the re-solution in the electrobl'e any agency which tends to cause the time during which these agencies are most active. y

(d) From the above, it may be nferred that any motion of the mercury a disadvantage, and it has been found by experi ment that the rate of re-solution of the sodium increases very rapidly with the agita tion of the mercury. It is necessary in practree to have some circulation of the mercury but the ill effect of the agitation involved is reduced by shortening the period of agitation, or by reducing the agitation itself.

(e) A further disadvantage in the commercial cells lies in the fact that the mercury cathode surface is usually greater than the active anode surface. It has been established that the ampere efficiency at the cathode, within practicable limits, rises with the increase of the current density. The maximum current densityis'limited, not by the capacity of the mercury cathode but by the capacity of the graphite anode. If too high a current density is used at the anode, the graphite will be rapidly eaten away and the increased capacity will be obtained only at a sacrifice of the costly anodes; Byihaving the anode surface larger than the cathode surface, it is ossible to obtain the desired high current ensity at the cathode without running the density at the anode above the critical point. In this Way efficiency is gained at the cathode without undue attack on the anodes.

f) In most commercial cells anode and cathode surfaces are not strictly parallel, but there exists such differences in the current path between the electrodes as result in a preciable differences in the richness of t 1e amalgam at different portions of the surface of the cathode. Thisresults in local action similar to that occurring in the case of the patches above referred to, and reduces the efficiency of the cell.

The disadvantages above noted are avoided or minimized by conducting the electroly sis under conditions as hereinafter set forth.

For a full understanding of my invention reference is made to the accompanying drawin s, wherein:

Figure 1 is a transverse vertical section on line 11 of Fig. 2, of one form of electrolytic cell for carryin my method into effect; Fig. 2 is a horizontal section of the same on line 22 of Fig. 1; Fig. 3 is a horizontal section of a slightly modified form of cell; and Fi 4 is a partial verticalsection on line 44 of Fig. 3..

The apparatus shown'comprises a covered containing vessel 1, of slate, cement, lass, earthenware or other material capable of withstandin the action of the products of electrolysisjiaving inlet and outlet ipes 2, 3 for brine, and a chlorin outlet 4. iipon the bottom of the cell I provide an desired number of s aced blocks 5, usuall y of the same materia as the container 1, each block usually having a very slightly concaved u per surface 6 and a central aperture 7. T iese blocks support thin iayers, of mercury 8 which constitute the cathode, this mercury being supplied through ipes 9, 10. In the use of the amalgam farthic reparat1on-of hydroxid solutions the supp y of mercury will be derived from an oxidizing cell or cells as is well understood. .The spacedblocks 5- provide intermediate communicating channels llfor the reception of the amalgam, these channels being provided'with one or more draw-off pipes 12, leading in case caustic soda is to be prepared, to the. oxidizing cell above referred to. In order that the quantity of mercury incircuit may not be excessive, I prefer to reduce the area of the 30 channels 11 oy blocks 13 suitably disposed therein, these blocks consisting also of re fractory material and projecting somewhat above the surface of the mercury. The mercury supporting blocks 5 are preferably 5 of comparatively small sizes, say two to four inches in diameter, and it will be understood that their number may be multiplied as desired to secure increased-cell'ca acity.

In the particular form of ceii illustrated the anodes comprise rectan ular blocks 14, preferably of Acheson graphite, extending above a row of mercury-supporting blocks 5 and projecting somewhat beyond them as indicated, this construction providing an anode surface which is strictly parallel with that of the cathode and of 'reater area. Current connection is established through' graphite lugs 15 extending through the cover of the cell.

To protect the amalgam in the channels 11 from the action of the electrolyte it maybe kept in electrical contact with the cathode as through pi e 12, and may also be covere with an insu atin body 16, which may be a heavy non-cond uctive liquid inert to the products of electrolysis, or which may co1nprise a non-conductive and inert solid, as quartz sand, floating upon the amalgam.

In Figs. 3, 4, I have s i fied form of apparatus wherein the mercurysupporting blocks- 5 are elongated and rovided with elongated inlet apertures or s ots 7. The form or configuration of these blocks may be varied as desired. In this construction the channel 11 may be reduced to a mere slot having an area exposed to the electro l te sufficient only to convey the amalgam, the mercury being at full flow. As shown in Figs. 3, 4, this is accomplished by refractory blocks 13 as in Figs. 1, 2, but it will be obvious that the same result may be secured by disposing the blocks 5 in suitable proximity to the walls of the cell and to each other.

In the operation of the ap )aratus shown the flow of mercury through the cell may be continuous or intermittent. If-intermittent,

a large volume of mercury may be allowed to flow for a brief interval and thus the'amalgam cleared from the face of the cup more 9 own aslightly modi- 110 rapidly and more completely. In either from the edge are very rapidly pulled after the portions which are in the process of going over the edge, in fact at a velocity much greater than that of the flow of the main bulk of the mercury at the same point. This may be partiall due'to the fact that liquids flow more rapi ly at the surface than at the bottom or sides. It may also be partially due to the cohesion between the particles of amalgam, which pulls on the rear particles in much the same way that one car might pull a. train off the end of a trestle. A third mfluence may be the reduction of the surface tensionof the mercury due to the presence of foreign articles on its surface. t is beyond the reac of experimental evidence to prove whether one or all of these causes act, or in what relative degree they act, but the ultimate effect is as described and the amalgam is very rapidly removed from the face of the IIIBICH The ihllowing advantages of the above-described method may be noted:

1. The amalgam flows but a short distance in contact with the electrolyte, and the capacity of a single cell may be increased as desired without increasing the path of an iven portionof the amalgam within the cel his results in increased etticiency owing to the reduced loss of metal by re-solution in the electrolyte.

2. The time of contact of the mere with the electrolyte is further reduced, an local action is avoided, by the absence of any solid body or retardin surface in contact'with the amalgam'while the latter is within the field of electrolysis.

3. A comparativel hi h cathode current density may be employed, securing thereby increased cathode emciency and increased .5. The'method of cell capacity; this hi h cathode current den-' sity is rendered possible by the provision of active anode surfaces exceeding the active cathode surfaces in area,-and by the reduction in the path of flow of the amalgam and the duration of contact between the ama;

-gam and the electrolyte.

4. The parallelismof the electrodes diminishes loca action by avoiding variations in the richness of the amalgam at various points in contact with the electrolyte.

I claim:'

1. The method of producing amalgams and alloys which consists in passing an electric current to a lurality of independent bodies of fluid meta l beneath a common elec trolyte, and supplying the fluid metal to each of said bodies.

2. The method of producing am algams' and alloys which consists, in passin an electrio current to a plurality of ind ependent bodies of fluid metal beneath a common electrol te, and establishing a substantially radialf ow of the fluid metal in eachof said bodies. I

3. The method of producing amalgams and alloys which consistsin passing an electric current to a plurality of independent .bodies of fluid metal beneath a-connnon electrolyte, and intermittentl supplying the fluid metal to each of saidbo ies.'

4. The method of producing amalgams and alloys which consists in passing an electrio current from an anode to a fluid metal cathode, the anode being parallel to the cathode and having a greater active area, and removing the amalgam or alloy by a substantially radialfiow without contact with any retarding surface.

and alloys which consists in passing an electrio current from an anode to a fluid metal cathode, and removm the amalgam or alloy producing amalgams by a substantially radial flow out of contact with any retarding surface.

In testimony whereof, I afiix my signature in pre .ence of two witness a.

COURTLAND F. CARRIER, JR.-

Witnesses: W. J. WETMORE,

C. E. Hansen.

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