IUPAC-NIST Solubilities Database

IUPAC-NIST Solubility Database
NIST Standard Reference Database 106

Solubility System: Ammonium dihydrogenphosphate with Potassium dihydrogenphosphate and Water

Components:
   (1) Ammonium dihydrogenphosphate; NH4H2PO4; [7722-76-1]  NIST Chemistry WebBook for detail
   (2) Potassium dihydrogenphosphate; KH2PO4; [7778-77-0]  NIST Chemistry WebBook for detail
   (3) Water; H2O; [7732-18-5]  NIST Chemistry WebBook for detail

Original Measurements:
   Bergman, A.G.; Gladkovskaya, A.A.; Galushkina, R.A., Zh. Neorg. Khim. 1972, 17, 2055.

Variables:

   Concentration = Composition and temperature

Prepared By:
   J. Eysseltová

Experimental Remarks:

   Remarks: Compiler's comment: It is not possible to construct a legitimate phase diagram on the basis of the data that are given. The concentration of component added has the meaning given only if the added component is a salt. When water is the added component, the relation 100wwater = 100 – 100w_add is valid. With this assumption the following compositions of points lying on the transition curve were calculated (next page).

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

Table 1
t/°C	Chemical₁	Chemical₂	10² * Mass Fraction w₂^(a)	Solid Phase(s)^(b)
+6.0	12.5% KH2PO4 + 87.5% H2O	NH4H2PO4 (Component added)	11.5	A + B
+14.2	15.0% KH2PO4 + 85.0% H2O	NH4H2PO4	11.6	A + B
+17.6	15.0% KH2PO4 + 85.0% H2O	NH4H2PO4	17.3	A + B
-4.5	71.72% NH4H2PO4 + 28.28% KH2PO4	H2O	20.5	B + C
+25.0	71.72% NH4H2PO4 + 28.28% KH2PO4	H2O	32.6	A + B
-4.0	45.81% NH4H2PO4 + 54.19% KH2PO4	H2O	18.2	A + C
+13.6	45.81% NH4H2PO4 + 54.19% KH2PO4	H2O	24.5	A + B
+14.0	45.81% NH4H2PO4 + 54.19% KH2PO4	H2O	25.0	A + B
-3.6	25.0% NH4H2PO4 + 75.0% KH2PO4	H2O	14.3	A + C
-4.0	10.0% NH4H2PO4 + 90.0% H2O	KH2PO4	10.3	A + C

Table 2
t/°C	Chemical₁	10² * Mass Fraction w₁	m₁ [mol/kg]	Chemical₂	10² * Mass Fraction w₂	m₂ [mol/kg]	Chemical₃	10² * Mass Fraction w₃	Solid Phase(s)^(a)
+6.0	NH4H2PO4	11.50	1.29	KH2PO4	11.21	1.06	H2O	77.28	A + B
+14.2	NH4H2PO4	11.60	1.34	KH2PO4	13.44	1.32	H2O	74.95	A + B
+17.6	NH4H2PO4	17.30	2.15	KH2PO4	12.78	1.34	H2O	69.91	A + B
-4.5	NH4H2PO4	14.70	1.60	KH2PO4	5.80	0.53	H2O	79.50	B + C
+25.0	NH4H2PO4	23.38	3.01	KH2PO4	9.22	1.00	H2O	67.40	A + B
-4.0	NH4H2PO4	8.33	0.88	KH2PO4	9.86	0.88	H2O	81.80	A + C
+13.6	NH4H2PO4	11.22	1.29	KH2PO4	13.28	1.29	H2O	75.50	A + B
+14.0	NH4H2PO4	11.45	1.32	KH2PO4	13.55	1.32	H2O	75.00	A + B
-3.6	NH4H2PO4	2.58	0.24	KH2PO4	7.72	0.63	H2O	89.70	A + C
-4.0	NH4H2PO4	9.06	0.98	KH2PO4	10.30	0.94	H2O	80.63	A + C
-	The composition of the transition point is:	-	-	-	-	-	-	-	-
-4.5	NH4H2PO4	8.50	0.07	KH2PO4	11.40	0.53	H2O	80.10	A + B + C

Notes:
   Table 1  ^a  This is the mass % of component added.
   Table 1  ^b  The solid phases are: A=β solid solution; B=α-NH₄H₂PO₄; C=ice.
   Table 2  ^a  The solid phases are: A=β-solid solution; B=α-NH₄H₂PO₄; C=ice.

Method/Apparatus/Procedure:
   The only information given is that a visually polythermic method¹ was used.

Source and Purity of Materials:
   Chemically pure salts were recrystallized and dried before use. Bidistilled water was used

Estimated Errors:
   Solubility: No information is given.
   Temperature: No information is given.

References:
   ¹Bergman, A.G.; Luzhnaya, N.P. Fiziko-Khimicheskie Osnovy Izucheniya i Ispol'zovaniya Solyanykh Mestorozhdeniy Khlorid-sul'fatnogo Tipa, Moscow, IAN SSSR, 1951.