Dec. 5 , 1954
SOLUBILITY I N THE SYSTEM
[CONTRIBUTION FROM
THE
L4LUMINUMPHOSPHATE-PHOSPHORIC
A~CID-nr.iTRR
5051
DIVISIONO F CHEMICAL DEVELOPMENT, TENNESSEE VALLEY AUTHORITY]
Solubility in the System Aluminum Phosphate-Phosphoric Acid-Water BY J. C. BROSHEER, F. A. LENFESTY AND J. F. ANDERSON, JR. RECEIVED APRIL 19, 1954 Solubilities were determined in the system AlPO~-H~POd-H20a t 25,50 and 75'. Although the liquid phases reached equilibrium in less than 5 months, many of the solid phases apparently did not reach equilibrium. The solid phases are AlPO4.nH10, in which x is less than 3 and decreases with increase in temperature; an intermediate acid salt that is probably AlPOa. H3POd.3HzO; and an acid salt, AlPOa.2H3P04. The system is similar to the system FePOd-H3POd-H20. The aluminum salts are considerably more soluble, however, than the corresponding iron salts.
Iron and aluminum occur in rock phosphate and must be reckoned with in acidulation processes for converting the rock to fertilizer. The formation of iron and aluminum compounds in phosphate systems is a part of the chemistry of the acidulation processes.
tative information on the corresponding aluminum phosphate system was lacking, however, when the present determinations of solubilities a t 25, 50 and 75' were made. Bailer' reported that Erlenmeyer found only two aluminum phosphates, AlP04.2Hz0and A1P04.2H3P04.
TABLE I THESYSTEM A1PO4-HsPOa-HZ0AT 25 AlaOa
0.00 0.04 0.46 1.06 1.07 2.01 2.19 2.25 2.24 3.03 4.50 4.23 4.66 5.46 6.17 6 . 15 7.31 7.32 7.40 6.03 7.65 8.58 7.93 6.57 8.ril 7.44
Liquid phase, % PnOs AlPOi
0.00 1.06 5.09 8.46 8.68 11.90 12.37 14.01 14.02 16.81 22.57 23.21 23.74 26.32 28.18 29.94 33.13 34.20 34.65 32.56 3.5.15 36.48 36.52 35.75 38,32 37.00 8.84 39.07 6.41 37.17 6.49 38.47 6.45 38.85 6.29 42.79 6.28 43.09 6.14 45.84 5.93 46.78 6.03 49.44 6.73 53.15 7.25 54.57 a Slightly exceeds the
\
Hap01
AltOa
0.00 0.00 14.29" 0.10 1.38 16.76 1.11 6.13 11.oo 2.54 11.23 9.64 2.56 7.60 9.93 12.56 4.82 5.78 12.86 5.25 16.93 5.39 15.01 13.85 15.04 12.11 5.37 7.25 17.38 6.80 22.51 10.76 14.42 23.91 10.12 6.75 11.15 23.81 11.92 13.06 25.85 11.07 14.77 27.03 14.83 29.52 14.71 17.48 12.62 31.69 17.51 15.07 33.15 17.71 33.61 16.98 14.42 33.37 6.49 18.31 16.35 33.82 20.54 14.19 34.86 18.96 17.42 35.19 15.71 36.74 15.56 20. 35 36.57 8.51 17 80 12.17 36.78 21.15 36.95 10.29 15.33 13.48 39.00 15.52 40.65 13.15 15.44 41.23 14.21 15.06 46.98 16.37 15.02 47.42 14.85 14.70 51.48 10.64 14.19 53.18 10.05 14.42 56.68 8.95 16.10 60.4.5 11.55 17.35 61.40 12.29 Alp04 equivalent of the P20s.
...
Wet solids, % Pa05 Alp04
HIP04
...
Solid phase
19.59 23.58 17.46 20.13 16.00 16.41 28.25 25.60 23.97 20.51 30.31 24.75 28.21 30.16 42.05
33.65 40.10 26.31 26.86 18.18 13.83 40.50 33.14 28.97 16.26 34.49 16.16 28.52 26.48 35.49
0.34 2.97 6.21 7.49 11.54 6.46 8.72 9.81 15.25 14.14 21.19 16.03 20.36 29.54
AlPOi.xHz0 AlP0d.xHZO AlPOd.xHz0 AlP04.xHzO AlPOi.xHz0 AlPO4.xHzO AlPO4.xHzO AlPOi.xH20 AlP04.xHzO AlP04.xHzO AlPO4.xHzO AlPOi.xHz0 AlPOd.xHz0 AlP04.xH20 A~PO~.H~PO~.~HZO
34.93 44.94 47.61 32.36 45.56 39.51 47.94 46.69 38.26 42.24 39.12 45.31 46.08 47.11 49.64 48.51 47.07 48.51 50.27 52.15 54.24
30.20 36.05 40.62 15.53 39.13 33.95 41.68 37.22 20.37 29.11 24.61 32.24 31.46 33.99 39.16 35.52 25.45 24.05 21.41 27.63 29.41
23.96 33.08 33.09 32.20 31.47 27.27 32.69 34.55 36.46 34.93 34.23 36.65 38.34 37.73 37.06 38.44 44.54 47.65 52.20 49.80 51.25
Metastable Metastable Metastable AlPOd.xHz0 Metastable Metastable Metastable AIPOI~H~PO~.~H~O Metastable Metastable Metastable AlPOa.HaPOa.3HrO AlPO4.H3POa,3HZO AlPOa.HaPOa.3HzO AIPOI.HIPO~.~H?O AlPO4.HsPOa.3HZO AlPOa,H3POd,3Hz0 AlPO4.HaPO4.3H20 AlPOd.HsP01.3Hz0 AIPOd.HsPO4.3H20 AlPOi.H3P04,3HzO
...
...
...
. .. . . . . .
Solubilities in the system iron phosphate-phosphoric acid-water have been reported.'+ Quanti-
After the present solubility measurements were completed, GuCrin and Martin7 reported somewhat
(1) A. Bailer, thesis, Stuttgart, 1930. ( 2 ) E. B. Brutskus, Trans. Sci. Ins!. Fcrliliecrs and Inscctofungicidcs (U.S.S.R.), 137, 110 (1937). (3) F. K. Cameron and J. M. Bell, J . Phrs. Chem.. 11. 363 (1907).
(4) S. R. Carter and N. H. Hartshorne, J . Chcm. Soc.. 123, 2223 (1923). (6) S. R. Carter and N. H. Hartshorne, ibid., 363 (1926). (6) R. F. Jameson and J. E. Salmon, ibid., 28 (1954). (7) H. Guerin and R. Martin, Compl. rend., 234, 1777 (1952).
J. C.RROSIIRRR,
59.;.
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A.
LENFESTY AND
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I-01. 76
ANDERSON, JR
TABLE I1 THESYSTEM A1POa-H3P04-H20AT 50' All01
0.01 0.10 0.36 0.65 1.14 1.73 1.89 3.70 4.79 6.02 6.84 7.31 7.47 7.74 7.47
- --
.a3
7.*52 7.90 8.43 8 ,0 3 6.2C 2 OR
0.05 3.60 6.35 8.62 11.39 14.77 15.39 22.53 27.02 31.44 34.65 36.02 37.69 38.82 43.71 46.27 47.18 50.86 52.98 54.22 55.60 60.05
0 01 0 24 0 86 1 55 2 72 4 14 451 8 8.5 11 45
14 41 16 36 17.49 17 87 18 52 17 88 18 07 18 00 18 91 20.11 20 6
