US902157A - Process for producing phosphoric acid. - Google Patents

Description

F. J. MAYWALD.

PROCESS FOR. PRODUCING PHOSPHORIG AGID..

APPLICATION FILED SEPT. 10, 1902.

902,157. Patented Oct. 27, 1908.

WITNESSES: INVENTOR 97 ll. I V K BY )1 ATTORNEY UNiTnD STATES PATENT orTicE.

PROCESS FOR PRODUCING PHOSPHORIC ACID.

Specification of Letters Patent.

Patented Oct. 27, 1908.

Application filed SeptemberlO, 1902. Serial No. 122,759.

To all whom it'may concern:

Be it known that I, FREDEIHCK J. MAP warn, a citizen of the United States, residing in Brooklyn, in the county and State of New York, have invented a Process of Producing Phosphoric Acid; and I do hereby declare the following to be afull, 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.

My invention relates to a process of producing phosphoric acid from natural phosphates, such as are known as phosphate rock, and is applicable to aluminum phosphate, calcium phosphate, and mixtures of calcium and aluminum phosphates and calcium, aluminum and iron phosphates. These phosphates having an earthy base of alkaline earth or earthy oXid are all relatively infusible.

The process consists in passing an electric current through a mass of the coi mninuted material, and collecting the fumes evolved, preferably by condensing them to a powder, which is readily soluble in water. Under the conditions of operation, as hereinafter set forth, the phosphate simply dissociates and the P 0, distils away, leaving a residue of base or basic phosphate. The P 0 is collected as such The objects of my invention are, to produce phosphoric acid in a simple and inexpensive manner and in a readily soluble form.

In the dravsiings which accompany and form a part of this specification, I illustrate diagrammatically an apparatus which may be used for carrying out my process.

Said apparatus consists of a crucible 1, which may be of plumbago or graphite or other suitable material, and may Vided at its bottom with an aperture through which may be inserted a carbon electrode 2. Above this crucible is a condensing hood 3 for collecting the fumes evolved and insaid hood is an aperture through which mav be inserted another carbon electrode 4. The

hood may be constructed of metal and if radiation to the surrounding atmosphere is not suflicient to keep it cool, it may becooled artificially, as by blowing a blast 'of air upon it.

A dynamo or-other generator 5 is placed in circuit with the carbon electrodes 2 and 4, and in this circuit there may be an adjustableresistance 6.

be pro- I In carrying out the process, the material to be used is placed, preferably in a finely pulverized condition, within the crucible, retort, furnace or other object within which the process is conducted. A trace of carbon in the material will often aid in the evolution of the phosphoric acid if the material be diflicult to dissociate. But the addition of carbon is not ordinarily necessary. I ordinarily employ a current of from 40 to volts. The voltage is higher at the beginning of the operation, but as the mass becomes hot the voltage will fall of itself.

It is preferable to employ a short are, the carbon electrodes being placed close together, as there is then less tendency to produce phosphorus than when a long arc is used. But I have found resistance heating to be effective; the resistance heating being effected by separating the carbons when the mass within the crucible is hot, so that 'no distinct arc is produced but the electric current permeates the mass of granular material between the two electrodes. temperature of the mass is kept below the melting point thereof, as I have found that if the mass be heated to the melting point it is impracticable to drive off all of'the phosphoric acid. But when not heated to the melting point, the mass remains in a porous condition, which permits free escape of phosphoric acid.

A slight amount of air may be permitted to enter the crucible or furnace to oxidize any phosphorus that may be formed. Such air may be introduced through a slight space left between the crucible and condensing hood or by other suitable means.

The result of the passage of the electric current is to dissociate the phosphate and liberate the phosphoric acid in a anhydrous form from the material treated, and the fumes of this anhydrous acid or P 0 condense upon the hood 3 as a powder which is readily soluble in cold water. From time to time the hood 3 may be removed and the powder which thus collects dislodged therefrom. I

I do not limit myself to the use of the particular apparatus shown in the drawings, or to the use of any particular apparatus, or to any particular material from which to form the crucible or furnace, or the electrodes, or the condensing hood; nor do I limit myself to any particular form of condensing apparatus, nor to any particular In any case, the

strength of current. Likewise, the process may e applied to the extraction of phosphoric acid from other salts of said acid than are above specified.

Having thus completely described my invention, What I claim and desire to secure by Letters Patent is:

1. The process of treating phosphates which consists in producing a low potential are in a granular mass of phosphates having an earthy base and heating such phosphates to a dissociating temperature, thereby decomposing the same into phosphoric oxid and base, and in collecting the fumes of phosphoric oXid as such.

The process of treating phosphates which consists in. subjecting a granular mass of phosphates having an earthy base to heat. and the action of a short electric arc and heating such phosphates to a dissociating temperature, thereby decomposing the same into phosphoric oxid and a basic residue, and in collecting evolved fumes of phosphoric 0Xi(l.

3. The process of treating phosphates which consists in subjecting a granular mass of relatively infusible phosphates to heat and the action of a short electric arc While permitting access of air to such mass, and heating such phosphates to a dissociating temperature, thereby decomposing said phosphates into phosphoric oxid and a basic residue, and in collecting the evolved fumes of phosphoric oxid.

4:.- The. process of treating phosphates Which consists in subjecting a granular mass of relatively infusible phosphates to the action of the are produced by an electric current not materially exceeding 60 volts in potential, and heating such phosphates to a dissociating temperature, thereby decomposing said phosphates into phosphoric oxid and a basic residue, and in collecting the fumes of phosphoric oxid produced.

5. The process of treating phosphates which consists in initially heating a granular mass of relatively infusible phosphates by means of a short'electric are produced by an electric current not materially exceeding- (30 volts in potential, continuing the heating by passing a low potential current through said granular mass and heating such phosphates to a dissociating temperature thereby decomposing the same into phosphoric oxid and a basic residue, and in collecting the fumes of phosphoric ,oxid

' produced.

In testimony whereof I affix my signature, in the presence of two witnesses.

FREDERICK J. MAYVALD.

'VVitnesses H. M. NIARBLE, A. H. PERLES.

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