IUPAC-NIST Solubility Database
NIST Standard Reference Database 106

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 Solubility System: Ammonium dihydrogenphosphate with Ammonium fluorosilicate and Water

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Components:
   (1) Ammonium dihydrogenphosphate; NH4H2PO4; [7722-76-1]  NIST Chemistry WebBook for detail
   (2) Ammonium fluorosilicate; (NH4)2[SiF6]; [16919-10-0]  NIST Chemistry WebBook for detail
   (3) Water; H2O; [7732-18-5]  NIST Chemistry WebBook for detail

Original Measurements:
   Morgunova, E.M.; Maslova, N.D.; Golovina, V.I., Zh. Neorg. Khim. 1972, 17, 2006.

Variables:

   Concentration = Composition and temperature

Prepared By:
   J. Eysseltová

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

Solubility isotherms in the (NH₄)₂[SiF₆]-NH₄H₂PO₄-H₂O system.

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)
25	(NH4)2[SiF6]	18.70	1.29	NH4H2PO4	---	---	H2O	81.30	A
25	(NH4)2[SiF6]	18.01	1.26	NH4H2PO4	1.66	0.18	H2O	80.33	A
25	(NH4)2[SiF6]	16.59	1.16	NH4H2PO4	3.38	0.37	H2O	80.03	A
25	(NH4)2[SiF6]	15.47	1.10	NH4H2PO4	5.62	0.62	H2O	78.91	A
25	(NH4)2[SiF6]	13.50	0.98	NH4H2PO4	9.33	1.05	H2O	77.17	A
25	(NH4)2[SiF6]	12.42	0.92	NH4H2PO4	11.50	1.31	H2O	76.08	A
25	(NH4)2[SiF6]	11.59	0.87	NH4H2PO4	13.48	1.56	H2O	74.93	A
25	(NH4)2[SiF6]	10.96	0.83	NH4H2PO4	15.20	1.79	H2O	73.84	A
25	(NH4)2[SiF6]	10.11	0.78	NH4H2PO4	16.93	2.02	H2O	72.96	A
25	(NH4)2[SiF6]	9.55	0.74	NH4H2PO4	18.02	2.16	H2O	72.43	A
25	(NH4)2[SiF6]	9.26	0.73	NH4H2PO4	19.48	2.38	H2O	71.26	A
25	(NH4)2[SiF6]	8.59	0.69	NH4H2PO4	21.34	2.65	H2O	70.07	A
25	(NH4)2[SiF6]	7.97	0.64	NH4H2PO4	22.42	2.80	H2O	69.61	A
25	(NH4)2[SiF6]	7.80	0.64	NH4H2PO4	23.60	2.99	H2O	68.60	A + B
25	(NH4)2[SiF6]	7.06	0.58	NH4H2PO4	24.53	3.12	H2O	68.41	B
25	(NH4)2[SiF6]	5.45	0.45	NH4H2PO4	25.87	3.27	H2O	68.68	B
25	(NH4)2[SiF6]	3.65	0.29	NH4H2PO4	26.89	3.37	H2O	69.46	B
25	(NH4)2[SiF6]	1.84	0.15	NH4H2PO4	28.11	3.49	H2O	70.05	B
25	(NH4)2[SiF6]	---	---	NH4H2PO4	29.77	3.69	H2O	70.23	B
50	(NH4)2[SiF6]	25.77	1.95	NH4H2PO4	---	---	H2O	74.23	A
50	(NH4)2[SiF6]	22.13	1.76	NH4H2PO4	7.17	0.88	H2O	70.70	A
50	(NH4)2[SiF6]	17.26	1.40	NH4H2PO4	13.57	1.71	H2O	69.17	A
50	(NH4)2[SiF6]	12.77	1.09	NH4H2PO4	21.54	2.85	H2O	65.69	A
50	(NH4)2[SiF6]	9.75	0.87	NH4H2PO4	27.34	3.78	H2O	62.91	A
50	(NH4)2[SiF6]	7.80	0.72	NH4H2PO4	31.72	4.56	H2O	60.48	A + B
50	(NH4)2[SiF6]	4.07	0.38	NH4H2PO4	35.13	5.02	H2O	60.80	B
50	(NH4)2[SiF6]	---	---	NH4H2PO4	43.95	6.82	H2O	56.05	B
75	(NH4)2[SiF6]	32.30	2.68	NH4H2PO4	---	---	H2O	67.70	A
75	(NH4)2[SiF6]	25.16	2.14	NH4H2PO4	8.88	1.17	H2O	65.96	A
75	(NH4)2[SiF6]	20.69	1.81	NH4H2PO4	15.07	2.04	H2O	64.24	A
75	(NH4)2[SiF6]	7.17	0.80	NH4H2PO4	42.35	7.29	H2O	50.48	A + B
75	(NH4)2[SiF6]	6.30	0.72	NH4H2PO4	44.33	7.81	H2O	49.37	B
75	(NH4)2[SiF6]	3.30	0.37	NH4H2PO4	46.26	7.97	H2O	50.44	B
75	(NH4)2[SiF6]	---	---	NH4H2PO4	55.66	10.91	H2O	44.34	B
90	(NH4)2[SiF6]	35.82	3.13	NH4H2PO4	---	---	H2O	64.18	A
90	(NH4)2[SiF6]	33.16	2.83	NH4H2PO4	1.14	0.15	H2O	65.70	A
90	(NH4)2[SiF6]	27.08	2.40	NH4H2PO4	9.71	1.34	H2O	63.21	A
90	(NH4)2[SiF6]	22.06	2.01	NH4H2PO4	16.48	2.33	H2O	61.46	A
90	(NH4)2[SiF6]	17.72	1.71	NH4H2PO4	24.27	3.64	H2O	58.01	A
90	(NH4)2[SiF6]	18.86	1.96	NH4H2PO4	27.21	4.39	H2O	53.93	A
90	(NH4)2[SiF6]	11.17	1.25	NH4H2PO4	38.52	6.66	H2O	50.31	A
90	(NH4)2[SiF6]	9.02	1.06	NH4H2PO4	43.18	7.85	H2O	47.80	A
90	(NH4)2[SiF6]	7.13	0.87	NH4H2PO4	46.95	8.89	H2O	45.92	A
90	(NH4)2[SiF6]	6.40	0.80	NH4H2PO4	48.44	9.32	H2O	45.16	A + B
90	(NH4)2[SiF6]	4.98	0.60	NH4H2PO4	48.74	9.16	H2O	46.28	B
90	(NH4)2[SiF6]	2.82	0.34	NH4H2PO4	51.17	9.67	H2O	46.01	B
90	(NH4)2[SiF6]	1.11	0.13	NH4H2PO4	51.87	9.59	H2O	47.02	B
90	(NH4)2[SiF6]	---	---	NH4H2PO4	61.85	14.09	H2O	38.15	B

Notes:
   Table 1  ^a  These values were calculated by the compiler. The unit is: mol kg^–1.
   Table 1  ^b  The solid phases are: A=(NH₄)₂[SiF₆]; B=NH₄H₂PO₄.

Method/Apparatus/Procedure:
   The isothermal method was used. The samples were equilibrated in polyethylene vessels at 25 °C and 50 °C, and in ebonite vessels at 75 °C and 90 °C. Equilibrium was attained in 3 weeks at 25 °C, in 7 days at 50 °C and in 2 days at 75 °C and 90 °C. The composition of the solid phases was determined by the Schreinemakers' method. Ammonium was determined by the distillation method. [SiF₆]^2– was determined by precipitation as K₂[SiF₆].¹

Source and Purity of Materials:
   (NH₄)₂[SiF₆] was prepared from reagent grade H₂[SiF₆] (MRTU 609-4821-67) and recrystallized. NH₄H₂PO₄ was prepared as described by others.²

Estimated Errors:
   Solubility: No information is given.
   Temperature: The temperature was controlled to within ± 0.1 K. No other information is given.

References:
   ¹Ricci, J.E.; Skarulis, J.A. J. Am. Chem. Soc. 1951, 73, 3624.
   ²Karyakin, Yu.V. Chistye Khimicheskiye Reaktivi Leningrad, Goskhimizdat 1947.

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Last updated: February 18, 2015 (Created: August 17, 2007)