IUPAC-NIST Solubilities Database

IUPAC-NIST Solubility Database
NIST Standard Reference Database 106

Solubility System: Ammonium dihydrogenphosphate with Sodium dihydrogenphosphate and Water

Components:
   (1) Ammonium dihydrogenphosphate; NH4H2PO4; [7722-76-1]  NIST Chemistry WebBook for detail
   (2) Sodium dihydrogenphosphate; NaH2PO4; [7558-80-7]  NIST Chemistry WebBook for detail
   (3) Water; H2O; [7732-18-5]  NIST Chemistry WebBook for detail

Original Measurements:
   Shpunt, S.Ya., Zh. Prikl. Khim. (Leningrad) 13, 9 (1940).

Variables:

   Concentration = Temperature and composition.

Prepared By:
   J. Eysseltová

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

Part 1. Crystallization temperatures on sections of the NaH₂PO₄-NH₄H₂PO₄H₂O system.
Solution number	t/°C	Chemical₁	10² * Mass Fraction w₁	m₁ [mol/kg]^(a)	Chemical₂	10² * Mass Fraction w₂	m₂ [mol/kg]^(a)	Solid Phase(s)^(b)
I	-2.1	NaH2PO4	7.7	0.70	NH4H2PO4	----	----	A
I	-3.3	NaH2PO4	7.4	0.70	NH4H2PO4	4.8	0.48	"
I	-4.5	NaH2PO4	7.0	0.70	NH4H2PO4	9.1	0.94	"
I	-5.5	NaH2PO4	6.8	0.71	NH4H2PO4	13.0	1.41	"
I	-0.6	NaH2PO4	6.5	0.70	NH4H2PO4	16.7	1.89	B
I	8.5	NaH2PO4	6.2	0.70	NH4H2PO4	20.0	2.36	"
I	17.1	NaH2PO4	6.0	0.70	NH4H2PO4	23.1	2.83	"
I	25.0	NaH2PO4	5.8	0.71	NH4H2PO4	25.9	3.30	"
I	30.8	NaH2PO4	5.6	0.71	NH4H2PO4	28.6	3.78	"
II	-4.5	NaH2PO4	15.4	1.52	NH4H2PO4	----	----	A
II	-5.0	NaH2PO4	15.0	1.52	NH4H2PO4	2.9	0.31	"
II	-5.6	NaH2PO4	14.6	1.53	NH4H2PO4	5.7	0.62	"
II	-6.1	NaH2PO4	14.2	1.53	NH4H2PO4	8.3	0.93	"
II	-6.7	NaH2PO4	13.9	1.54	NH4H2PO4	10.7	1.23	"
II	1.4	NaH2PO4	13.2	1.54	NH4H2PO4	15.2	1.84	B
II	8.9	NaH2PO4	12.8	1.52	NH4H2PO4	17.3	2.15	"
II	13.6	NaH2PO4	12.5	1.53	NH4H2PO4	19.3	2.46	"
II	19.8	NaH2PO4	12.2	1.53	NH4H2PO4	21.3	2.78	"
II	24.5	NaH2PO4	12.0	1.53	NH4H2PO4	23.1	3.09	"
II	30.1	NaH2PO4	11.7	1.54	NH4H2PO4	24.8	3.39	"
III	-6.6	NaH2PO4	23.1	2.50	NH4H2PO4	----	----	A
III	-7.1	NaH2PO4	22.7	2.51	NH4H2PO4	2.0	0.23	"
III	-7.6	NaH2PO4	22.2	2.50	NH4H2PO4	3.8	0.45	"
III	-8.0	NaH2PO4	21.8	2.50	NH4H2PO4	5.7	0.68	"
III	-8.5	NaH2PO4	21.4	2.50	NH4H2PO4	7.4	0.90	"
III	-9.0	NaH2PO4	21.0	2.50	NH4H2PO4	9.1	1.13	"
III	-2.2	NaH2PO4	20.3	2.50	NH4H2PO4	12.2	1.57	B
III	3.5	NaH2PO4	19.9	2.50	NH4H2PO4	13.8	1.81	"
III	7.9	NaH2PO4	19.6	2.50	NH4H2PO4	15.2	2.03	"
III	13.1	NaH2PO4	19.2	2.52	NH4H2PO4	17.3	2.37	"
III	29.0	NaH2PO4	18.7	2.51	NH4H2PO4	19.3	2.70	"
III	26.1	NaH2PO4	18.1	2.50	NH4H2PO4	21.3	3.06	"
III	30.1	NaH2PO4	17.7	2.49	NH4H2PO4	23.1	3.39	"
IV	-2.7	NaH2PO4	34.6	4.41	NH4H2PO4	----	----	C
IV	-2.6	NaH2PO4	33.9	4.41	NH4H2PO4	2.0	0.27	"
IV	-2.5	NaH2PO4	33.2	4.39	NH4H2PO4	3.8	0.52	"
IV	-2.6	NaH2PO4	32.6	4.40	NH4H2PO4	5.7	0.80	"
IV	-2.5	NaH2PO4	32.0	4.40	NH4H2PO4	7.4	1.06	"
IV	-2.9	NaH2PO4	31.5	4.42	NH4H2PO4	9.1	1.33	"
IV	1.9	NaH2PO4	30.9	4.41	NH4H2PO4	10.7	1.59	B
IV	9.0	NaH2PO4	30.4	4.41	NH4H2PO4	12.2	1.85	"
IV	13.9	NaH2PO4	29.9	4.42	NH4H2PO4	13.8	2.13	"
IV	18.5	NaH2PO4	29.4	4.42	NH4H2PO4	15.2	2.38	"
IV	27.6	NaH2PO4	28.4	4.41	NH4H2PO4	18.0	2.92	"
V	7.1	NaH2PO4	38.5	5.22	NH4H2PO4	----	----	C
V	6.8	NaH2PO4	37.8	5.23	NH4H2PO4	2.0	0.29	"
V	6.9	NaH2PO4	37.1	5.23	NH4H2PO4	3.8	0.56	"
V	7.2	NaH2PO4	36.4	5.24	NH4H2PO4	5.7	0.86	"
V	7.1	NaH2PO4	35.8	5.25	NH4H2PO4	7.4	1.13	"
V	7.1	NaH2PO4	35.2	5.26	NH4H2PO4	9.1	1.42	"
V	7.1	NaH2PO4	34.5	5.24	NH4H2PO4	10.7	1.70	B + C
V	12.1	NaH2PO4	33.9	5.24	NH4H2PO4	12.2	1.97	B
V	17.9	NaH2PO4	33.3	5.24	NH4H2PO4	13.8	2.27	"
V	22.8	NaH2PO4	32.8	5.26	NH4H2PO4	15.2	2.54	"
V	27.3	NaH2PO4	32.2	5.25	NH4H2PO4	16.7	2.84	"
VI	14.5	NaH2PO4	42.3	6.11	NH4H2PO4	----	----	C
VI	14.4	NaH2PO4	41.4	6.09	NH4H2PO4	2.0	0.31	"
VI	14.7	NaH2PO4	39.9	6.11	NH4H2PO4	5.7	0.91	"
VI	14.6	NaH2PO4	38.4	6.09	NH4H2PO4	9.1	1.51	"
VI	14.5	NaH2PO4	37.1	6.10	NH4H2PO4	12.2	2.09	"
VI	20.9	NaH2PO4	36.4	6.09	NH4H2PO4	13.8	2.41	B
VI	26.6	NaH2PO4	35.9	6.12	NH4H2PO4	15.2	2.70	"
VI	31.1	NaH2PO4	35.2	6.10	NH4H2PO4	16.7	3.02	"
VII	-8.4	NaH2PO4	24.9	2.91	NH4H2PO4	3.8	0.46	A
VII	-8.8	NaH2PO4	26.6	3.18	NH4H2PO4	3.7	0.46	"
VII	-9.7	NaH2PO4	28.2	3.44	NH4H2PO4	3.6	0.46	"
VII	-8.2	NaH2PO4	31.1	3.96	NH4H2PO4	3.5	0.46	C
VII	-5.3	NaH2PO4	32.5	4.22	NH4H2PO4	3.4	0.46	"
VII	-1.2	NaH2PO4	34.1	4.54	NH4H2PO4	3.3	0.46	"
VII	3.4	NaH2PO4	36.5	5.04	NH4H2PO4	3.2	0.46	C
VII	7.8	NaH2PO4	38.5	5.49	NH4H2PO4	3.1	0.46	"
VII	15.6	NaH2PO4	41.9	6.32	NH4H2PO4	2.9	0.46	"
VII	20.8	NaH2PO4	44.8	7.12	NH4H2PO4	2.8	0.46	"
VII	24.3	NaH2PO4	46.1	7.50	NH4H2PO4	2.7	0.46	"
VIII	-7.9	NaH2PO4	19.9	2.30	NH4H2PO4	8.0	0.96	A
VIII	-8.7	NaH2PO4	22.0	2.61	NH4H2PO4	7.8	0.96	"
VIII	-9.3	NaH2PO4	23.8	2.89	NH4H2PO4	7.6	0.96	"
VIII	-9.9	NaH2PO4	25.6	3.18	NH4H2PO4	7.4	0.96	"
VIII	-10.7	NaH2PO4	27.3	3.47	NH4H2PO4	7.2	0.96	A + C
VIII	-8.0	NaH2PO4	28.8	3.74	NH4H2PO4	7.1	0.96	C
VIII	-3.3	NaH2PO4	31.7	4.29	NH4H2PO4	6.8	0.96	"
VIII	1.5	NaH2PO4	34.1	4.79	NH4H2PO4	6.6	0.97	"
VIII	6.5	NaH2PO4	36.5	5.33	NH4H2PO4	6.4	0.97	"
VIII	10.7	NaH2PO4	38.5	5.80	NH4H2PO4	6.2	0.97	"
VIII	14.7	NaH2PO4	40.2	6.22	NH4H2PO4	6.0	0.97	"
VIII	18.3	NaH2PO4	41.9	6.68	NH4H2PO4	5.8	0.96	"
VIII	23.5	NaH2PO4	44.8	7.52	NH4H2PO4	5.6	0.98	"
VIII	28.2	NaH2PO4	47.3	8.31	NH4H2PO4	5.3	0.97	"

Part 2. Solutions coexisting with two solid phases
t/°C	Chemical₁	10² * Mass Fraction w₁	m₁ [mol/kg]^(a)	Chemical₂	10² * Mass Fraction w₂	m₂ [mol/kg]^(a)	Chemical₃	10² * Mass Fraction w₃	Solid Phase(s)^(b)
-4.3	NaH2PO4	----	----	NH4H2PO4	16.7	1.74	H2O	83.3	A + B
-9.9	NaH2PO4	32.4	3.99	NH4H2PO4	----	----	H2O	67.6	A + C
-6.0	NaH2PO4	6.6	0.70	NH4H2PO4	14.7	1.62	H2O	78.7	A + B
-7.1	NaH2PO4	13.6	1.53	NH4H2PO4	12.4	1.46	H2O	74.0	"
-9.1	NaH2PO4	21.0	2.53	NH4H2PO4	9.8	1.23	H2O	69.2	"
-2.8	NaH2PO4	31.3	4.39	NH4H2PO4	9.3	1.36	H2O	59.4	B + C
7.1	NaH2PO4	34.4	5.22	NH4H2PO4	10.7	1.69	H2O	54.9	"
14.7	NaH2PO4	37.3	6.09	NH4H2PO4	11.7	1.99	H2O	51.0	"
-10.2	NaH2PO4	30.0	3.75	NH4H2PO4	3.4	0.44	H2O	66.6	A + C
-10.7	NaH2PO4	27.4	3.49	NH4H2PO4	7.2	0.96	H2O	65.4	"

Part 3. Solubility isotherms.
t/°C	Chemical₁	Composition₁^(c)	10² * Mass Fraction w₁	m₁ [mol/kg]^(a)	Chemical₂	Composition₂^(c)	10² * Mass Fraction w₂	m₂ [mol/kg]^(a)	Chemical₃	Composition₃^(c)	10² * Mass Fraction w₃	Solid Phase(s)^(b)
-9.9	NH4H2PO4	---	---	---	NaH2PO4	100.0	32.4	3.99	H2O	1391	67.6	A + C
-9.9	NH4H2PO4	11.7	3.6	0.46	NaH2PO4	88.3	28.6	3.51	H2O	1400	67.8	A
-9.9	NH4H2PO4	24.0	7.5	0.96	NaH2PO4	76.0	24.6	3.02	H2O	1398	67.9	"
-9.9	NH4H2PO4	29.6	9.2	1.18	NaH2PO4	70.4	22.8	2.79	H2O	1402	68.0	A + B
-9.9	NH4H2PO4	23.8	8.5	1.17	NaH2PO4	76.2	28.4	3.75	H2O	1129	63.1	B + C
-9.9	NH4H2PO4	10.4	3.4	0.45	NaH2PO4	89.6	30.4	3.83	H2O	1302	66.2	C
-7	NH4H2PO4	---	---	---	NaH2PO4	100.0	24.2	2.66	H2O	2092	75.8	A
-7	NH4H2PO4	16.5	4.0	0.46	NaH2PO4	83.5	21.0	2.33	H2O	1988	75.0	"
-7	NH4H2PO4	33.5	8.4	0.98	NaH2PO4	66.5	17.4	1.95	H2O	1893	74.2	"
-7	NH4H2PO4	48.1	12.3	1.45	NaH2PO4	51.9	13.8	1.56	H2O	1851	73.9	A + B
-7	NH4H2PO4	34.6	10.6	1.34	NaH2PO4	65.4	20.8	2.53	H2O	1436	68.6	B
-7	NH4H2PO4	23.7	8.8	1.24	NaH2PO4	76.3	29.4	3.96	H2O	1068	61.8	B + C
-7	NH4H2PO4	19.8	7.0	0.96	NaH2PO4	80.2	29.7	3.91	H2O	1140	63.3	C
-7	NH4H2PO4	10.0	3.4	0.45	NaH2PO4	90.0	31.5	4.03	H2O	1239	65.1	"
-7	NH4H2PO4	---	---	---	NaH2PO4	100.0	33.6	4.22	H2O	1261	66.4	"
-4.3	NH4H2PO4	---	---	---	NaH2PO4	100.0	15.1	1.48	H2O	3745	84.9	A
-4.3	NH4H2PO4	56.8	8.8	0.91	NaH2PO4	43.2	7.0	0.69	H2O	3484	84.2	"
-4.3	NH4H2PO4	100.0	16.8	1.76	NaH2PO4	---	---	---	H2O	3184	83.2	A + B
-4.3	NH4H2PO4	70.9	15.3	1.70	NaH2PO4	29.1	6.6	0.70	H2O	2309	78.1	B
-4.3	NH4H2PO4	50.8	13.3	1.58	NaH2PO4	49.2	13.5	1.54	H2O	1782	73.2	"
-4.3	NH4H2PO4	36.4	11.4	1.46	NaH2PO4	63.6	20.6	2.52	H2O	1396	68.0	"
-4.3	NH4H2PO4	23.8	9.1	1.30	NaH2PO4	76.2	30.3	4.16	H2O	1015	60.6	B + C
-4.3	NH4H2PO4	18.9	6.9	0.96	NaH2PO4	81.1	31.0	4.16	H2O	1084	62.1	C
-4.3	NH4H2PO4	9.5	3.3	0.45	NaH2PO4	90.5	32.8	4.28	H2O	1175	63.9	"
-4.3	NH4H2PO4	---	---	---	NaH2PO4	100.0	34.6	4.41	H2O	--- (d)	65.4	"
0	NH4H2PO4	100.0	18.4	1.96	NaH2PO4	---	---	---	H2O	2833	81.6	B
0	NH4H2PO4	73.4	16.9	1.92	NaH2PO4	26.6	6.4	0.70	H2O	2127	76.7	"
0	NH4H2PO4	65.0	16.06	1.86	NaH2PO4	35.0	9.02	1.00	H2O	1941	74.92	"
0	NH4H2PO4	54.0	14.7	1.77	NaH2PO4	46.0	13.1	1.51	H2O	1697	72.2	"
0	NH4H2PO4	42.6	13.11	1.66	NaH2PO4	57.4	18.46	2.25	H2O	1420	68.43	"
0	NH4H2PO4	40.1	12.9	1.67	NaH2PO4	59.9	20.0	2.48	H2O	1333	67.1	"
0	NH4H2PO4	28.5	10.53	1.48	NaH2PO4	71.5	27.47	3.69	H2O	1077	62.0	"
0	NH4H2PO4	25.1	10.0	1.48	NaH2PO4	74.9	31.1	4.40	H2O	944	58.9	"
0	NH4H2PO4	24.1	9.64	1.43	NaH2PO4	75.9	31.69	4.50	H2O	937	58.67	B + C
0	NH4H2PO4	24.3	9.8	1.46	NaH2PO4	75.7	31.7	4.51	H2O	931	58.5	"
0	NH4H2PO4	17.4	6.7	0.97	NaH2PO4	82.8	33.2	4.60	H2O	999	60.1	C
0	NH4H2PO4	15.3	5.8	0.83	NaH2PO4	84.7	33.5	4.60	H2O	1024	60.7	"
0	NH4H2PO4	8.8	3.2	0.45	NaH2PO4	91.2	34.8	4.68	H2O	1083	62.0	"
0	NH4H2PO4	7.3	2.62	0.36	NaH2PO4	92.7	34.84	4.64	H2O	1109	62.54	"
0	NH4H2PO4	---	---	---	NaH2PO4	100.0	36.4	4.77	H2O	1150	63.6	"
+10	NH4H2PO4	100.0	21.8	2.42	NaH2PO4	---	---	---	H2O	2288	78.2	B
+10	NH4H2PO4	77.6	20.5	2.43	NaH2PO4	22.4	6.2	0.70	H2O	1766	73.3	"
+10	NH4H2PO4	59.7	18.0	2.26	NaH2PO4	40.3	12.7	1.53	H2O	1470	69.3	"
+10	NH4H2PO4	46.4	16.1	2.16	NaH2PO4	53.6	19.4	2.51	H2O	1196	64.5	"
+10	NH4H2PO4	30.5	12.7	1.93	NaH2PO4	69.5	30.2	4.41	H2O	875	57.1	"
+10	NH4H2PO4	26.0	11.5	1.84	NaH2PO4	74.0	34.1	5.22	H2O	788	54.4	"
+10	NH4H2PO4	24.6	11.1	1.81	NaH2PO4	75.4	35.5	5.54	H2O	757	53.4	B + C
+10	NH4H2PO4	14.6	6.2	0.96	NaH2PO4	85.4	38.0	5.67	H2O	838	55.8	C
+10	NH4H2PO4	7.3	3.0	0.45	NaH2PO4	92.7	39.5	5.72	H2O	900	57.5	"
+10	NH4H2PO4	---	---	---	NaH2PO4	100.0	40.5	5.67	H2O	961	59.5	"
+20	NH4H2PO4	100.0	25.9	3.04	NaH2PO4	---	---	---	H2O	1824	74.1	B
+20	NH4H2PO4	81.4	24.2	3.00	NaH2PO4	18.6	5.7	0.68	H2O	1508	70.1	"
+20	NH4H2PO4	64.9	21.4	2.80	NaH2PO4	35.1	12.1	1.52	H2O	1293	66.5	"
+20	NH4H2PO4	51.8	19.5	2.75	NaH2PO4	48.2	18.9	2.56	H2O	1048	61.6	"
+20	NH4H2PO4	36.1	15.8	2.50	NaH2PO4	63.9	29.2	4.42	H2O	806	55.0	"
+20	NH4H2PO4	31.5	14.5	2.40	NaH2PO4	68.5	32.9	5.21	H2O	730	52.6	"
+20	NH4H2PO4	27.6	13.4	2.33	NaH2PO4	72.4	36.7	6.13	H2O	658	49.9	"
+20	NH4H2PO4	24.9	12.4	2.22	NaH2PO4	75.1	39.1	6.72	H2O	621	48.5	B + C
+20	NH4H2PO4	12.2	5.7	0.96	NaH2PO4	87.8	42.9	6.95	H2O	701	51.4	C
+20	NH4H2PO4	6.2	2.8	0.45	NaH2PO4	93.8	44.2	6.95	H2O	750	53.0	"
+20	NH4H2PO4	---	---	---	NaH2PO4	100.0	45.3	6.90	H2O	789	54.7	"
+30	NH4H2PO4	100.0	30.2	3.76	NaH2PO4	---	---	---	H2O	1477	69.8	B
+30	NH4H2PO4	84.0	28.0	3.66	NaH2PO4	16.0	5.5	0.70	H2O	1278	66.5	"
+30	NH4H2PO4	73.6	26.10	3.54	NaH2PO4	26.4	9.77	1.27	H2O	1156	64.13	"
+30	NH4H2PO4	69.5	25.2	3.46	NaH2PO4	30.5	11.5	1.51	H2O	1116	63.3	"
+30	NH4H2PO4	56.9	23.0	3.40	NaH2PO4	43.1	18.2	2.58	H2O	930	58.8	"
+30	NH4H2PO4	45.6	20.0	3.16	NaH2PO4	54.4	24.97	3.78	H2O	802	55.03	"
+30	NH4H2PO4	40.7	18.6	3.04	NaH2PO4	59.3	28.2	4.42	H2O	745	53.2	"
+30	NH4H2PO4	36.1	17.1	2.96	NaH2PO4	63.9	31.9	5.23	H2O	678	50.8	"
+30	NH4H2PO4	32.3	16.2	2.91	NaH2PO4	67.7	35.4	6.09	H2O	617	48.4	"
+30	NH4H2PO4	31.6	15.78	2.82	NaH2PO4	68.4	35.62	6.11	H2O	622	48.60	"
+30	NH4H2PO4	24.9	13.30	2.58	NaH2PO4	75.1	41.89	7.79	H2O	536	44.81	B + C
+30	NH4H2PO4	24.9	13.20	2.54	NaH2PO4	75.1	41.60	7.67	H2O	544	45.20	"
+30	NH4H2PO4	18.5	9.55	1.78	NaH2PO4	81.5	43.75	7.80	H2O	580	46.70	C
+30	NH4H2PO4	12.3	6.26	1.15	NaH2PO4	87.7	46.50	8.20	H2O	594	47.24	"
+30	NH4H2PO4	10.2	5.2	0.96	NaH2PO4	89.8	47.8	8.47	H2O	588	47.0	"
+30	NH4H2PO4	6.8	3.42	0.62	NaH2PO4	93.2	48.55	8.42	H2O	615	48.03	"
+30	NH4H2PO4	5.0	2.5	0.45	NaH2PO4	95.0	49.0	8.42	H2O	627	48.5	"
+30	NH4H2PO4	---	---	---	NaH2PO4	100.0	51.2	8.74	H2O	628	48.8	"

Notes:
   Table 2  ^a  The molalities were calculated by the compiler.
   Table 2  ^b  The solid phases are: A=ice; B=NH₄H₂PO₄; C=NaH₂PO₄·2H₂O.
   Table 3  ^a  The molalities were calculated by the compilers.
   Table 3  ^b  The solid phases are: A=ice; B=NH₄H₂PO₄; C=NaH₂PO₄·2H₂O.
   Table 3  ^c  The composition units are: mol/100 mol of solute.
   Table 3  ^d  The compiler calculates this missing value to be 1259.

Method/Apparatus/Procedure:
   A standard visual polythermic method and the isothermal method were used but no details are given. The P₂O₅ content was determined by a standard method described in the "NIUIF materials" but no reference is given. The ammonia content was determined by the Kjeldahl method. The sodium ion content was probably determined by difference--compiler.

Source and Purity of Materials:
   No information is given.

Estimated Errors:
   Solubility: No information given.
   Temperature: The temperature was controlled to within ± 0.2 K.