US1484734A

US1484734A - Method and apparatus for making fluorine

Info

Publication number: US1484734A
Application number: US309254A
Authority: US
Inventors: Frank C Mathers; Humiston Burr
Original assignee: Individual
Current assignee: Individual
Priority date: 1919-07-07
Filing date: 1919-07-07
Publication date: 1924-02-26
Anticipated expiration: 1941-02-26

Description

Feb. 26 1924.:

F. C. MATHERS ET AL METHOD AND APPARATUS FOR MAKING FLUORINE Filed July '7, 1919 z r r W 3 A if 3 Lmmm m fi 1 will I AH IIII 3 I W ulmiizmgnzl M M 1W FRANK C. MATHERS, OF BLO'OMINGTON, INDIANA, ,AND BURIR HUMISTON, OF WIL- I MINGTON, DELAWARE.

METHOD AND APPARATUS FOR MAKING FLUORINE.

Application filed July 7, 1919. Serial No. 809,254.

To all whom it may concern:

Be it known that we, FRANK C. MATHERS and Bum: HUMISTON, citizens of the United States, and residing at Bloomington, In-

6 diana, and Wilmington, Delaware, respectively, have invented certain new and useful Improvements in Methods and Apparatus for Making Fluorine, of which the following is a specification.

This invention relates to a novel method and apparatus for making fluorine.

()ne of the objects of this invention is to provide a method and means for producing fluorine on a satisfactory commercial basis and on as large a scale as desired, and

to eliminate disadvantageous conditions existing in the prior processes.

Another object of this invention is to provide an apparatus for making fluorine wherein the heating is so distributed that no excessive local heating results but the electrolyte is heated in. a substantially, uniform manner.

Another object of this invention is to zfi'provide the apparatus with means for avoiding the necessity of using an excessive electromotive force for decomposing the electrolyte. I

Reference is to be had to the accompanyso ing drawing in which the preferred form of our apparatus is shown.

The vessel (1) contains the electrolyte (2) in which the diaphragm (3) is partly submerged. This diaphragm is provided.

with openings or slots (4) near the lower portion thereof. The vessel.(1) and diaphragm (3) should be made of material which is not seriously attacked by either hydrofluoric acid or by fluorine. In our 4.0 preferred form of apparatus we make these parts of graphite, carbon or copper; the

rarbon, graphite,-or copper vessel serving as the cathode.

The anode (5), which we have found should preferably be made of graphite, al-

though carbon may'be used, is located with in the diaphragm and in the upper portion thereof a copper lead (6) is secured and this passes out through the top (7) of the diaphragm (3). The fluorine which is evolved at the anode passes out by the way of the exit (8 In order to prevent the fluorine from escaping through the top (7) of the diaphragm, and to keep the anode as in proper position within the vessel and insulated from the vessel (1) and diaphragm (3), we have provided the top (7) with a gland (8) and nut (9). A washer (10) made of fluorspar or other material which is resistant to the action of fluorine and possesses insulating properties, is placed within the gland and serves to support the lead (6) and anode (5), the shoulders (11) on the lead (6) resting upon the washer (10). Powdered fluorspar or other insulating material which will withstand the action of fluorine is placed within the gland (8) and over the washer (10) and another washer (12), preferably made of material similar to that of (10) or of fiber since fluorine does not reach this point, is placed over the. powdered material which is held closely and firmly around the upper portion (13) of the lead (6) by means of the cap (9) screwed down on the gland (8). The positive terminal (14) of the electrolyzing current is joined to the lead (6), the negative terminal (15) being joined directly to the copper vessel (1) serving as a cathode.

Local heating of the bath, such as is obtained with a Bunsen burner, is objectionable because where the heat is localized there is overheating and this will cause the containing vessel to be attacked by the electrolyte. 35

We overcome the disadvantage of local heating by winding a suitable wire, such as nichrome wire (16) around the vessel (1) and insulating the wire from the vessel by means of asbestos paper (17). To prevent loss of heat by radiation the wires (16) are surrounded by asbestos wool (18) and asbestos paper (19). By passing an electric current through the wire, the vessel (1) and its contents will be heated and the heat will be uniformly distributed instead of localized.

The preferred form of electrolyte which we use is acid potassium fluoride, but it should be understood that other fluorides or 100 compounds of fluorine or mixtures thereof may be used which are not attacked by fluorine and which melt at a temperature at which the graphite anode and the containing vessel are not seriously attacked by 10 fluorine. Anhydrous potassium acid fluoride melts at approximately 220 C. and at this temperature decomposes but slightl A fresh bath prepared from KF and H generally contains some water which is removed by electrolyzing at a low current density before fluorine is obtained. If the current density is too high, polarization will result and the E. M. F. will rise to as much as 50 to 60 volts. A current of from 2 to 3 amperes per square decimeter is first passed through the electrolyte to remove any water contained therein. anode gas shows the presence of fluorine a much higher current density is used to effect electrolysis of fluorine. After the water is removed raising the current density does not produce polarization.

A satisfactory current density has been found to be 10 amperes per square decimeter, and an E. M. F. of 12'to 15 volts.

After the bath is subjected to electrolysis for a considerable length of time the electrolyte becomes viscous owing to the accumulation of KF and CuF where a copper vessel, diaphragm or false bottom is used. This results in frothing of the bath around the anode and may be remedied by removing the salt and grinding same and then-adding HF. In replenishing the salt with acid it is well to have a reasonable excess of-acid. At intervals it will be necessary to dissolve the bath in water and filter to remove accumullated copper fluoride and organic materia The bath should not be heated so low that the electrolyte will be too viscous, neither should it be heated so highly that HF will distil off too rapidly. At higher temperatures the conductivity of the bath is increased appreciably, but the loss of HF 0E- sets this advantage.

We provide the diaphragm with a false bottom (20) made of graphite, carbon or copper which prevents the hydrogen evolved at the bottom of the electrolyzing vessel from rising to the inside of the diaphragm where it would unite with the fluorine evolved at the anode. Ihe fluorine evolved at the anode collects within the dia phragm or cylinder (3). I

In our preferred form of apparatus we proposed to make the vessel (1), diaphragm (3), anode (5) and false bottom (20) of graphite, the graphite vessel (1) serving as the cathode. In this way, the bath of electrolyte contacts only with graphite and the objectionable formation of Cul when copper is used instead is avoided.

The present invention is not limited to the specific details set forth in the foregoing examples which should be construed as illustrative and not by way of limitation, and in view of the numerous modifications which may be aflected therein without departing from the spirit and scope of this invention it is desired that only such limitations be imposed as are indicated in the appended claims.

W e claim as our invention:

When a test of the 1. In an electrolytic apparatus formal:- ing fluorine, a graphite vessel for holding a bath of electrolyte and constituting the cathode, an anode of hardcarbonaceous material projecting into said vessel, means tori-" collecting the fluorine evolved at the anode comprising a diaphra surroundinggsaid anode, and means for lnsulating the ancde from the cathode and diaphragm and'fcr preventing the escape of fluorine whrc,

anode enters said diaphragm. 2. In an apparatus for making fluorinet, a cathode comprising a vessel, an anode of hard carbonaceous material projecting said vessel, a diaphragm su rroundlngsaid 0,,

a cathode comprising a graphite vessel, a graphite anode projecting into said vessel,

a diaphragm surrounding said anode, said diaphragm having openings near the lower extremity of the portion within the vessel and means for insulating the anode from the cathode and diaphragm and for preventing the escape of fluorine where anode enters said diaphragm.

'4. In an electrolytic apparatusfor mak ing fluorine, a vessel for holding a bath of electrolyte and constituting the cathode, an anode of hard carbonaceous material projecting into said vessel, means for collecting the fluorine evolved at the anode comprising a diaphragm surrounding said anode, means for insulating the anode from the cathode and diaphragm and for preventing the escape of fluorine where anode enters said diaphragm, and means for heating the bath in a substantially uniformly, distributive manner.

5. In combintion an anode compartment comprising means for collecting the fluorine evolved at the anode including a diaphra having openings at one end, saidanode eing of hard carbonaceous material, a cathode in the form of a vessel for holding an electrolyte, means for insulating the anode from the cathode and diaphragm and for preventing the escape of gas liberated at anode where the anode enters the anode compartment, and means for heating the bath in a substantially uniforml distributive manner.

6. In an electrolytic rocess of making fluorine with the aid of a hard carbona' ceous anode, heatin a fluoride in avessel the said vessel constituting the cathode and the heating being at a temperature at which the anode is substantially unattacked by fluorine and substantially, uniformly distributed throughoutthe electrolyte without causing objectionable local heating.

llllti 7. In an electrolytic process of making fluorine with the aid of a graphite anode, heating a fluorinde in a graphite vessel, the said vessel constituting the cathode and the heating being at a temperature at which the anode is substantially unattacked by fluorrine and substantially, uniformly distributed throughout the electrolyte without causing local heating.

8. In an electrolytic process of making fluorine with the aid of graphite anode, heating an acid-alkali metal fluoride in a graphite vessel, the said graphite vessel con stituting the cathode and the heating being substantially, uniformly distributed throughout the electrolyte without causing objectionable local heating.

9. A process of makin fluorine comprising electrolyzing a fused fluoride with an anode and cathode made of hard carbonaceous material and at a temperature at which the anode is substantially unattacked by fluorine. I

10. In a process of making fluorine, electrolyzing a fused fluoride with an anode and cathode made of graphite and at a temperature at which the anode is substantially unattacked by fluorine.

11. A process comprising the electrolysis with a hard carboneous anode and a hard carbonaceous cathode of an acid alkali metal fluoride in a state of fusion and collecting the evolved fluorine.

12. A process comprising the electrolysis with a graphite anode and graphite cathode of an acid alkali metal fluoride in a state of fusion and collecting the evolved fluorine.

13. A process of making fluorine comprising dehydrating a fused fluoride {by means of a current of low current density and then increasing the current density to that required for electrolysis.

14. A process of making fluorine comprising dehydrating a fused fluoride with a current of low current density and with an anode of hard carbonaceous material and then raising the current density to that required for electrolysis.

15. A process of making fluorine comprising dehydrating a fused fluoride with a current of low current density and with an anode of graphite and then raising the current density to that required for electrolysis.

16. A process of making fluorine comprising dehydrating a fused acid-alkali metal fluoride by .means of a current of low 7 current density and then increasing the current density to that required for electrolysis.

17. A process of making fluorine comprising dehydrating a fused acid-alkali metal fluoride with a current of low current density and with an anode of graphite and then raising the current density to that required for electrolysis.

FRANK O. MATHERS.

BURR HISTON.