US1150900A - Manufacture of monoalkali-metal phosphate. - Google Patents

Description

ATE F EMEEsoN H. STRICKLER, OF NEW YORK, N. Y., AssIe oE' T0 GENERAL CHEMICAL",

COMPANY, on NEW YORK, N. Y., A CORPORATION OF NEW YORK.

MAN'tTFACTURE OF MONOALKALI-ME'IAL PHOSPHATE.

No Drawing.

To all whom it may concern Be it known that I, EMERSON H. STRIQK- LER, a .citizenjof the United States, and a resident of the city of New York, State of' New York, have invented certain new and useful Im rovements in the Manufacture of Monoalka i-Metal Phosphate, of which the following is a. specification.

My invention relates to the manufacture of mono-alkali metal phosphates, an example of which is mono-sodium phosphate which is stated to have, apart from water of crystallization, the formula NaH,PO'

An object of my'invention is to provide a novel process for the production of monoalkali metal phosphates by which a substantially pure product. is capable of being obtained on a commercial scale and at a commercially reasonable cosh;

Another object is to provide a cyclic process for the production of mono-alkali metal phosphate in which the residue, after the mono-alkali metal phosphate has been separated out, is introduced into an earlier stage of the complete process, such as that stage at which tri-alkali-metal phosphate is made for example in accordance with the r-ocess set forth in my Letters Patent No. 744,128, dated November 17, 1903, or in my Letters Patent No. 1,037,837, dated September 3,1912. y Other objects will be pointed out or will otherwise appear in the following description of my invention, in which, as well as in the appended claims, I use the term alkali metal phosphate to include the diand tri-alkali-metallic salts of phosphoric acid,

such as .or potassium; di-alkali metal phosphate to includedi-sodium phosphate and di-potassium phosphate; trialkalimetal phosphate to include tri-sodium phosphate and tri-potassium phosphate; mono-alkali metal phosphate to nclude mono-sodium phosphate and monopotassium hosphate; and acid to include 1 acids free om phosphorus, such as sulfuric,

nitric and hydrochlorieacids.

Heretofore. IIlOIlO-SOdllJIIl phosphate has been a laboratory product only. The laboratory methods of producing it are (1) treating phosphoric acid (H P carbonate until the mixture is neutral, using methyl orange as an indicator; '(2) treating phosphate or di-sodium phos- Speeifieatio'n of Il'etters Patent.-

, with sodium phate with phosphoric acid; or, (3) adding alcohol to a solution of di-sodium phosphate in nitric acid.

For commercial and technical purposes,

commercial and technical operations and,

which contaminate the mono-sodium phosphate produced therefrom in accordance with the first two of the above methods, and,

in the 'case of thethird laboratory method,-

owing to the prohibitive cost of, the alcohol. On the other hand' my improved process of making mono-alkali metal phosphates, which, of course, includes mono-sodium phosphate, is both a commercially available process and'one which results in a product commercially free from 1ron,'alumma, and

Patented Aug. 24., 1915.

Application filed March 23, 1912. Serial No. ceases.

the other impurities above mentioned, a

product which is only accompanied by small and for practical purposes, negligible amounts of other alkali metal salts, such as, for example, sodium sulfate, sodium I chlorid, sodium nitrate. By proper methods of purification,.-such as crystallization, the

amounts of such accompanying salts can be reduced to any desired degree.

Broadly stated my invention consists in treating an alkali metal phosphate with an .acid free from phosphorus, such as sulfuric acid, hydrochloric acid,- or nitric .acid, in such a manner as to liberate all the phosphoric acid contained in the alkali metal phosphate, separating the phosphoric acid from the salt of the acid which has been used'and treating the phosphoric'acid with a further amount of alkali metal phosphate in such a manner as to produce mono-alkali metal phosphate. The liquor containing phosphoric acid and thesalt of the added acid is preferably treated to separate its constituentsby removing the .salt of the added acid. It is obvious that the removal of the salt-of the added acid maybe effected subsequently to the final addition of alkali metal phosphate, but this method is found not to be so-eflicient' as the first mentioned process.

.When" the phosphoric acid is separated ess of making mono-alkali metal phosphate.

There is thus evolved a cyclic process in which all of thealkali metal products of phosphoric acid are utilized. The mono-- alkali metal phosphate, moreover, is produced in a substantially pure condition. In

this cyclic process, a complete separation of the phosphoric acid and the salt of the added acid is obviously unnecessary because in any case all of the phosphorus contained' in the original phosphate is utilized.

In the practice. of that example of my cyclic process in which I employ sulfuric acid as the added acid and which includes the process set forth in the above Patent 744,128, tri-sodium phosphate is made by treating. rock phosphate 5. 6. calcium phosphate with a solution of niter cake and furnacing the solution thus obtained in the presence of a carbonaceous material, thetrisodium phosphate thus made is then treated with sulfuric acid in such a manner as to produce phosphoric acid 'andrsodium sulfate, the last mentiond constituents are then separated and the sodium sul:

1 fate, carrying with it small amounts of phosphate, is then utilized; as ,above set forth, 1n the manufacture of more tri-sodi- 'um phosphate. The phosphoric acid is treated with a further amount of tri-sodium phosphate to produce mono-sodium phos-' phate. I have-described my cyclic process in which sulfuric acid is used and the sulfate of soda produced-is employed in the preparationof the tri-sodium phosphate. It will be understood, however, that the salts of the other added acids may by suitable modifications be employed with equally successful results. If another acid than sulfuric has beenused, the salt of the added acid may obviously be converted into a sulfate by treatment with sulfuric acid so that the processes hereinbefore referred tomay be utilized for producing tri-alkali metal phosphate. To the sodium sulfate, produced or recovered whatever way, the proper amount of crude phosphoric acid should be added so that the proportion between the sulfur and the phosphorus in the resulting mix is that prescribed in my above referred'to patent.

Various methods may be used to separate the constituents of the liquor roduced by the treatment of alkali metal p osphate;

with acid. Furthermore, the processes of my invention are susceptible of various slight changes in detail.

To illustrate the nature of my invention the following examples are given. These examples are to be considered as illustrative only.

OPERATING WITH DI-S ODIUM PHOSPHATE.

Crystallized di-scdium' phosphate, contains approximately 12 molecular proportions of water of crystallizatlon; z'. 6. ap-' proximately 60% of water. In carrying out my new process with this product I have found it advantageous to take into account the solvent action of the water so introduced into the process and in the case of an acid containing much water such as strong hydrochloric acid, weak sulfuric acid or aweak nitric acid to use even practically dehydrated di-sodium phosphate.

Tri-sodium phosphate may stead-of di-sodium phosphatein all of the processes described for the latter, the proc-' esses and results being substantially the same. A. Using sulfuric acid as the added acid.

Example 1.

' Add sulfuric acid, preferably in the'form of a 98% acid to sodium phosphatecrystals or solution (crystals preferred) until the mixture is neutral to methyl orange; then add a further quantity of sulfuric acid equal to that? required for neutralization; boil.

be used 'indown until a sample of the solution when filtered fromthe. undissolved material yields a filtrate which tests 60 Be and remove the solidby filtering or otherwise.

To the filtrate add di-sodium phosphate until it tests neutral to methyl-orange;

.then concentrate-to 50 Be and proceed to separate the mono-sodium phosphate bv cooling and crystallizing.

B. Using hydrochlil'rcz'z as the added Y Example 2.- Neutralize di-sodium phosphate with hydrochloric acid using methyl orange as indicator. Then add a further quantity of hydrochloric acid equal in amount to that first added; concentrate the mixture by evaporation until a sample portion of the mixture yields a filtrate which tests 5860 B. Then separate the undissolved material by filtratlon or otherwlse. It s preferable to allow the mixture to cool before making-the separation. The separated salt 'is principally sodium chlorid.

filtrate add 'di-sodlum phosphate To, the v until it is neutral to methyl orange; allow to cool and crystallize. The crystals thus obtained are mono-sodium phosphate.

I Concentrate the mother liquor by evaporation and again crystallize. The crystals C. Using nitric acid as the added acid;

Ewampie 3.

Neutralize di-sodium phosphate with nitric acid, using methyl orange as an 1nd1- cator. Concentrate by evaporation until the mixture, with its suspended solids,tests 64 -B'; addan amount of concentrated nitric acid equal to that required for neutralization; cool and separate by filtering or other;- wise. The separated material is largely if not wholly sodium nitrate. Concentrate the filtrate to 60 B' by boiling; add disodium phosphate until the solution is neutral to methyl orange; concentrate to 55? B The crysand allow to cool and crystallize. tals are mono-sodium phosphate.

The mother liquor may be, concentrated and crystallized. The final "liquors including the sodium nitrate crystals separated above are used for making sodium phosphate.

The several grades of mono-sodium phosphate obtained in all the foregoing examples are, if necessary, further purified by suitable crystallization; applying the ordinary experience .andrules obtaining in such practice, the mono-sodium phosphate can be freed from accompanying salts of the added acids to any extent needful in commercial operation. In the preceding examples, furthermore, trisodiumphosphate may be used in-' stead of di-sodium phosphate, with correspondingly similar results, the proportions of theadded materials, of course, being difacid and treating the phosphoric acid with suflicient alkali metal phosphate to produce mono-alkali metal phosphate, substantially as described.

2. The process of making mono-alkali metal phosphate which consists in treating alkali metal'phosphate with sufficient acid to produce free phosphoric acid and an alkali metal salt of the added acid, suitably concentrating this product to precipitate the salt of the addedacid, removing the precipitated salt from the phosphoric acid, and treating. j I

the phosphoric acid withsuflicient' alkali metal phosphate to produce mono-alkali metal phosphate, substantially as described.

3. The cyclic process of making monoalkali metal phosphate which consists in treating alkali metal phosphate with sufiicient acid to produce free phosphoric acid and an alkali metal salt of the added acid, separating the last-mentioned salt and the phosphoric acid, treating the phosphoric acid with sufiicient alkali metal phosphate to produce mono-alkali metal phosphate, converting the separated salt of the added acid into alkali metal phosphate and utilizingthe last mentioned alkali metal phosphate in a repetition of the above operations, substantially as described. v

4. The cyclic process of making monoalkali' 'metal phosphate which consists in first making trialkali "metal phosphate by treating -a phosphate containing substance with an acid alkali metal sulfate and furnacing the result in the presence of a car-' bonaceous material, then treating the trialkali metal phosphate, thus produced with an acid. free from phosphorus to produce free phosphoric acid and an alkali metal salt of the added acid, then separating the last mentioned salt andthe phosphoric acid,

then. treating the phosphoric acid with sufli-s cient alkali metal phosphate to produce mono-alkali metal phosphate and then converting the separated salt of the added acid into acid alkali metal sulfate and utilizing the last mentioned acid alkali metal sulfate in a-repetition of the above operations, substantially as described.

t )5. The cyclic process of making'monosodium phosphate which consists in first making tri-sodium phosphate by treating a duced with sufficient sulfuric acid to produce free phosphoric acid and sodium sulfate, then separating the sodium sulfate and the phosphoric acid, then treatlng the phosphoric acid with suflicient sodlum phosphate to produce m'ono-sodiumphosphateand thenconverting the sodium sulfate into ,acid sodium sulfate and utilizing the last mentioned acid sodium sulfate in a repeti- 1 tion of the above operations, substantially as described.

In testimony whereof, I have hereunto set my hand in the. presence of two. subscribing witnesses. v v

' EMERSON-H. STRICKLER. Witnesses: a)

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