US1279593A - Process of producing perhalates. - Google Patents

Description

E. P. SCHOCH & R.- H.,PR|TCHETT. PROCESS OF PRODUCING PERHALATES.

APPLICATION FILED APR. 1B. 1918.

Patented Sept. 24, 1918.

. MAMA M AR.EPritc/0e y are.

EUGENE PAUL SCHOCH AND RUFUS HUBBARD PRITGHETT, OF AUSTIN, TEXAS.

PROCESS OF PRODUCING PERHALA'IES.

To all whom it may concern:

Be it known that we, EUGENE PAUL SoHooH and RUFUs HUBBARD PRrroHE'rT, both citizens of the United States, both residing at Austin, in the county of Travis and State of Texas, have invented certain new and useful Improvements in Processes of Producing Perhalates; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a process of producing perhalates, and especially perchlorates, andv their corresponding acids, through the use of an anode composed essentially of carbon, or silicon, and has for its object to' provide a method which will be simple to carry .outand more economical in practice than those heretofore proposed.

With these and other objects in view the invention consists in the novel steps and Specification of tte at n Patented Sept. 24,1918.

' Application filed April 18,

1918. Serial No. 229,382.

material; .and hence it was thought that such disintegration would be sufficient to destroy the anode to such an extent a to make the progess impracticable commercially.

l/Vinteler, in Zeitschm'ft ft'ir Elektrochemic, vol. 7 of 1901, p. 635, is authority for, and is probably one of the chief sources of the belief that a carbon anode cannot be substituted for platinumanode in an acid electrolyzing solution when producing perchlorates'on a commercial scale.

Further, it is a well recognized fact, that, if the solution is maintained neutral or alkaline throughout the process, the discharge potential from a carbon anode will not be great enough to commercially form perchlorates. Winteler really recognizes this fact also, for he states broadly that perchlorates cannot be formed at all with carbon electrodes.

We have discovered, on the other hand,

. that it is perfectlyfeasible to substitute carcombinations of steps involving the use of bon, or silicon, for platinum as anodes, in

a carbon or silicon anode, and constituting the process, all as will be more fully hereinafter disclosed and particularly pointed out in the claims.

Referring to the accompanying drawings forming a part of this specification in which views Figure 1 is a diagrammatic sectionalvi'ew, of an apparatus suitable for. carrying out' the invention; andt Fig. 2 is a plan view of the parts shown in Fig. 1.

1 indicate any suitable container, '2 any suitable electrolyte, such for example, as sodium chlorate, NaClO which may have an impurity such as sodium-chlorid mixed therewith, 3 any suitable carbon or silicon, or chemically similar anode, 4: any suitable metallic cathode such 'as copper gauze, nickel, iron, etc., and 5 a porous cup or other diaphragm surrounding the cathode 4, to separate the anode liquid from the cathode.

In order that .the precise invention may be the more clearly understood it is said Prior to our invention, it has been erroneou'sly believed that no commercial quantityof'perchlorates could be produced in an electrolytic cell using a carbon anode. This I ,erroneous belief has been founded partly on the fact that'the oxygen liberated at the car-j bon: anode in an acid solutiongives'rise' to avoided,.not only in the commercial production: of perchlorates in general, but also in I I the commercial production of perhalates. like numerals designate like parts in all the In carrying out our process, we employ an anode consisting essentially ofcarbon, or of silicon, and prefer to start with an acid solution of the chlorate corresponding to the perhalate to be made, but of course, we

may start with a neutral, or even an alkaline solution, and permit the action of the current to render the solution acid .asthe process proceeds.

Referring to the drawings, we prefer to .employ a current strength of from say ithree to twenty amperes per one hundred square centlmeters on the anode surface, and it is also preferred to keep the solution cold during the entire process. As the current passes I the usual cathode reactions take place in the hydroxid solution 6, provided of oourse,si1ch a solution surrounds the cathodes 4; and at the anode 3 likewise, the usual reactions will take place which in this case consists of the discharge of the oxygen ions fromthe wa- -ter, and the reaction of this oxygen with the chlorate ions at the surface of the carbon anode.

This last mentioned reaction will form perchlorate ions and free electrons which pass out through the pole. The hydrogen ions'left from thawater molecules,

of which the oxygen has been used up, re-

main .free in the solution and render th same acid in character.

We have found by actual tests that with an apparatus constructed as above described,

. 50% or greater of the total amount of curdecomposition.

rent employed. on. the other hand these results are impossible if the anode is in contact with an alkaline solution.

It will thus be seen that contrary to the statement of Winteler as well as of other authorities, not necessary to mention, and certainly contrary to the common belief among those skilled in the art, the substitution of carbon or silicon for the now almost prohibitive platinum is perfectly feasible in the manufacture of perchlorates at a commercial efficiency.

Our tests further show that although a small decomposition of the carbon anode actually takes place, yet, it has not proved to be at all prohibitive, and in some cases it has been as low as 9% by weight of the weight of the perchlorate produced.

In the absence of porous diaphragms, such as 5, the alkali produced by the pole reactions at the cathode will, of course,ten d toneutralize the acid produced at the anode, but the acidification of the liquid around the anode will increase unless the two liquids are properly mixed. If said liquids are mixed, of course, substantially no perchlorate at all will be formed. But, if the liquids are not mixed, the acidificatlon around. the anode will increase as the process continues, and will depend upon the distance the anode and cathode are separated.

In other words, when the liquids are not mixed, a slight acidity may be maintained around the anode and this acidity may be increased by the addition of acid from an extraneous source. Under these conditions, perchlorate has also been obtained by us in appreciable quantities. But, in such acidified solutions, the chlorate that comes in contact with the cathode is reduced to the chlorid, and when the chlorid thus formed comes in contact with the anode again, it becomes oxidized and thus it entails a waste of current in so far as the formation of perchlorate from chlorate is concerned.

Furthermore, this formation of the chlorid is objectionable for we have found in carrylng out our process that the\ extensive simultaneous oxidation of the chlorids at the anode increases ap reciably the carbon anode ence to overcome both of these sources of trouble, we have separated the cathodes 4 byporous diaphragms 5 fiom the anode liquid, thus preventing access of the acidified chlorate solutionto the cathode and its consequent reduction to the chlorid.

It will now be clear that by operating as above disclosed we are enabled to substitute the non-metallic elements of the carbon group, a. 9., carbon, and silicon, for the expensive platinum heretofore thought necessary for the production of perchlorates, and therefore, we are enabled to commercially produce not only a perchlorate of sodium' or potassium at a much less cost in the plant than was heretofore thought to be possible, but we are enabled to produce perhalates in general.

We have further discovered that the decomposition of the carbonand silicon anodes may be greatly diminished and the current efficiency increased, by the following treatment, preliminary to their use: heating the anodes, plunging them into a bath of melted parafin, ceresin, or ozocerite, and allowing them to remain until cool, whereupon the outer conducting surface may be exposed by mechanically cleaning ofl the excess of Waxlike material.

This treatment not only prevents the so1ution from penetrating into the pores of the anodes, thus causing a mechanical disintegration by the evolution of gases therein, etc., but it also limits theactive surface to an outer surface of known extent, and makes it possible to provide a definite current deni sity. This latter is very desirable, because, too low or too high a current density entails alower current efliciency.

We have found-the most eflicient formof carbon for our process to be that known as retortcarbon. In fact,: the retort carbon has been found to possess the surprising quality 105 of being a plurality of times more efficient .for this particular purpose than Acheson graphite. Of course, it is obvious that periodates, perbromates, and their corresponding acids maybe produced in'thesame mannor as the perchlorates, and the perchlorlc acid above mentioned; and it is further obvious that in addition to the employment of alkali metal chlorates as electrolytes, we may use any soluble chlorates, including chloric acid.

It is obvious that those skilled in the art may vary the process without departing from the spirit thereof, and therefore, we

2. The process of producing a perhalate in a commercial quantity which consists in electrolyzing the corresponding halate solution withan anode containing carbon and in contact with an acid solution, substan tially as described.

3. The process of producin a perchlorate which consists in electrolyzlng the corresponding acid chlorate solution with an anode comprising carbon, substantially as described.

4. The process of producing a perchlorate of an alkali metal which consists in electrolyzing the corresponding acid chlorate solution with a carbon anode, substantially as described.

5. The process of producing sodium perchlorate which consists in electrolyzing an acid solution of sodium chlorate with an anode of gas retort carbon, substantially as 20 described.

6. The process of producing sodium perchlorate and perchloric acid which consists in electrolyzing an acid solution of sodium chlorate, with an anode of carbon, and separating the anode liquid from the cathode, substantially as described.

In testimony whereof we allix our signatures.

EUGENE PAUL SCHOCH. RUFUS HUBBARD PRITGHETT.

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