IUPAC-NIST Solubilities Database

IUPAC-NIST Solubility Database
NIST Standard Reference Database 106

Solubility System: Ammonium dihydrogenphosphate with Diammonium hydrogenphosphate, Potassium sulfate and Water

Components:
   (1) Ammonium dihydrogenphosphate; NH4H2PO4; [7722-76-1]  NIST Chemistry WebBook for detail
   (2) Diammonium hydrogenphosphate; (NH4)2HPO4; [7783-28-0]  NIST Chemistry WebBook for detail
   (3) Potassium sulfate; K2SO4; [7778-80-5]  NIST Chemistry WebBook for detail
   (4) Water; H2O; [7732-18-5]  NIST Chemistry WebBook for detail

Original Measurements:
   Babenko, A.M.; Andrianov, A.M., Zh. Neorg. Khim. 1984, 29, 2663.

Variables:

   Concentration = Temperature and concentration of K₂SO₄ in a mixture containing a mol ratio of NH₄H₂PO₄/(NH₄)₂HPO₄ = 1.

Prepared By:
   J. Eysseltová

Experimental Data:   (Notes on the Nomenclature)
(Please see footnotes following the table(s).)

Part 1. Points of simultaneous crystallization of two or three solid phases in the NH₄H₂PO₄-(NH₄)₂HPO₄-K₂SO₄-H₂O system.
t/°C	Chemical₁	10² * Mass Fraction w₁	Chemical₂	10² * Mass Fraction w₂	m₂^(b)	Chemical₃	10² * Mass Fraction w₃	m₃^(b)	Chemical₄	10² * Mass Fraction w₄	m₄^(b)	Chemical₅	10² * Mass Fraction w₅	Solid Phase(s)^(c)
-1.6	mixture (a)	0	NH4H2PO4	0	0	(NH4)2HPO4	0	0	K2SO4	6.5	0.40	H2O	93.5	A + B
-4.0	mixture	9.0	NH4H2PO4	4.2	0.45	(NH4)2HPO4	4.8	0.45	K2SO4	10.0	0.71	H2O	81.0	"
-6.0	mixture	18.06	NH4H2PO4	8.41	1.01	(NH4)2HPO4	9.65	1.01	K2SO4	9.7	0.77	H2O	72.24	"
-9.0	mixture	27.3	NH4H2PO4	12.7	1.73	(NH4)2HPO4	14.6	1.73	K2SO4	9.0	0.81	H2O	63.7	"
-10.3	mixture	32.2	NH4H2PO4	15.0	2.18	(NH4)2HPO4	17.2	2.18	K2SO4	8.0	0.77	H2O	59.8	"
11.0	mixture	41.85	NH4H2PO4	19.48	3.311	(NH4)2HPO4	22.37	3.311	K2SO4	7.0	0.79	H2O	51.15	B + C
18.0	mixture	46.5	NH4H2PO4	21.6	4.05	(NH4)2HPO4	24.9	4.05	K2SO4	7.0	0.86	H2O	46.5	"
-8.6	mixture	38.6	NH4H2PO4	18.0	2.54	(NH4)2HPO4	20.6	2.54	K2SO4	0	0	H2O	61.4	A + C
-9.1	mixture	36.0	NH4H2PO4	16.8	2.40	(NH4)2HPO4	19.2	2.40	K2SO4	3.2	0.30	H2O	60.8	A + B + C
39.0	mixture	61.0	NH4H2PO4	28.4	6.33	(NH4)2HPO4	32.6	6.33	K2SO4	0	0	H2O	39.0	C + D
45.0	mixture	62.2	NH4H2PO4	29.0	7.19	(NH4)2HPO4	33.2	7.19	K2SO4	2.8	0.46	H2O	35.0	"

Part 2. Solubility isotherms in the NH₄H₂PO₄-(NH₄)₂HPO₄-K₂SO₄-H₂O system.
t/°C	Chemical₁	10² * Mass Fraction w₁	Chemical₂	10² * Mass Fraction w₂	m₂^(b)	Chemical₃	10² * Mass Fraction w₃	m₃^(b)	Chemical₄	10² * Mass Fraction w₄	m₄^(b)	Chemical₅	10² * Mass Fraction w₅	Solid Phase(s)^(c)
-5	mixture (a)	40.4	NH4H2PO4	18.8	2.74	(NH4)2HPO4	21.6	2.74	K2SO4	0	0	H2O	59.6	A
-5	mixture	37.0	NH4H2PO4	17.2	2.50	(NH4)2HPO4	19.8	2.50	K2SO4	3.15	0.30	H2O	59.85	"
-5	mixture	32.02	NH4H2PO4	14.91	2.179	(NH4)2HPO4	17.11	2.179	K2SO4	8.5	0.82	H2O	59.48	B
-5	mixture	27.2	NH4H2PO4	12.7	1.73	(NH4)2HPO4	14.5	1.73	K2SO4	9.2	0.83	H2O	63.6	"
-5	mixture	18.06	NH4H2PO4	8.41	1.01	(NH4)2HPO4	9.65	1.01	K2SO4	9.7	0.77	H2O	72.24	"
0	mixture	42.8	NH4H2PO4	19.9	3.03	(NH4)2HPO4	22.9	3.03	K2SO4	0	0	H2O	57.2	C
0	mixture	38.5	NH4H2PO4	17.9	2.67	(NH4)2HPO4	20.6	2.67	K2SO4	3.07	0.301	H2O	58.43	"
0	mixture	31.85	NH4H2PO4	14.83	2.179	(NH4)2HPO4	17.02	2.179	K2SO4	9.0	0.87	H2O	59.15	B
0	mixture	27.12	NH4H2PO4	12.63	1.734	(NH4)2HPO4	14.49	1.734	K2SO4	9.6	0.87	H2O	63.28	"
0	mixture	17.96	NH4H2PO4	8.361	1.011	(NH4)2HPO4	9.599	1.011	K2SO4	10.2	0.815	H2O	71.84	"
0	mixture	8.96	NH4H2PO4	4.17	0.450	(NH4)2HPO4	4.79	0.450	K2SO4	10.4	0.740	H2O	80.64	"
10	mixture	47.4	NH4H2PO4	22.1	3.65	(NH4)2HPO4	25.3	3.65	K2SO4	0	0	H2O	52.6	C
10	mixture	41.5	NH4H2PO4	19.3	3.02	(NH4)2HPO4	22.2	3.02	K2SO4	2.925	0.3020	H2O	55.575	"
10	mixture	31.64	NH4H2PO4	14.73	2.179	(NH4)2HPO4	16.91	2.179	K2SO4	9.6	0.94	H2O	58.76	B
10	mixture	26.91	NH4H2PO4	12.53	1.734	(NH4)2HPO4	14.38	1.734	K2SO4	10.3	0.941	H2O	62.79	"
10	mixture	17.8	NH4H2PO4	8.29	1.01	(NH4)2HPO4	9.51	1.01	K2SO4	11.0	0.887	H2O	71.2	"
10	mixture	8.88	NH4H2PO4	4.13	0.450	(NH4)2HPO4	4.75	0.450	K2SO4	11.2	0.804	H2O	79.92	"

Notes:
   Table 1  ^a  "Mixture" is an equimolar mixture of NH₄H₂PO₄ and (NH₄)₂HPO₄.
   Table 1  ^b  The molalities were calculated by the compiler. The units are: mol kg^–1.
   Table 1  ^c  The solid phases are: A=ice; B=K₂SO₄; C=NH₄H₂PO₄; D=(NH₄)₂HPO₄.
   Table 2  ^a  "Mixture" is an equimolar mixture of NH₄H₂PO₄ and (NH₄)₂HPO₄.
   Table 2  ^b  These values were calculated by the compiler. The units are: mol kg^–1
   Table 2  ^c  The solid phases are: A=ice; B=K₂SO₄; C=NH₄H₂PO₄; D=(NH₄)₂HPO₄.

Method/Apparatus/Procedure:
   An improved visual polythermic method¹ was used.

Source and Purity of Materials:
   Chemically pure or reagent grade salts were recrystallized twice and dried at 30 °C to 40 °C. The material designated "mixture" was prepared by mixing equimolar amounts of NH₄H₂PO₄ and (NH₄)₂HPO₄ and homogenizing by grinding in a mortar.

Estimated Errors:

   Temperature: Precision of temperature measurement was ±0.4 K.

References:
   ¹Erayzer, L.N.; Kaganskiy, I.M. Zavod. Lab. 1967, 1, 119.