Sodium tetraphosphate

Sodium tetraphosphate
Sodium tetraphosphate
Are common
Systematic ; name	Sodium tetraphosphate
Traditional names	Sodium phosphate; sodium tetramethaphosphate; sodium tetracyclophosphate
Chem. formula	Na 4 P 4 O 12
Physical properties
condition	colorless crystals
Molar mass	407.85 g / mol
Density	2,476 g / cm³
Thermal properties
T. decomp.	616 ° C
Classification
Reg. CAS number	13396-41-3
PubChem
Reg. EINECS number	236-482-6
Smiles
Inchi
ChemSpider

Sodium tetraphosphate is an inorganic compound, a salt of sodium and tetraphosphoric acid with the formula Na ₄ P ₄ O ₁₂ , colorless crystals, it dissolves in water, forms crystalline hydrates .

Content

Getting

Synthesis in two stages: dissolution of copper oxide in phosphoric acid with the formation of copper tetraphosphate

{\mathsf {2CuO+4H_{3}PO_{4}\ {\xrightarrow {}}\ Cu_{2}P_{4}O_{12}\downarrow +6H_{2}O}}

{\ displaystyle {\ mathsf {2CuO + 4H_ {3} PO_ {4} \ {\ xrightarrow {}} \ Cu_ {2} P_ {4} O_ {12} \ downarrow + 6H_ {2} O}}}

the resulting precipitate is added to a solution of sodium sulfide :

{\mathsf {Cu_{2}P_{4}O_{12}+2Na_{2}S\ {\xrightarrow {}}\ Na_{4}P_{4}O_{12}+2CuS\downarrow }}

{\ displaystyle {\ mathsf {Cu_ {2} P_ {4} O_ {12} + 2Na_ {2} S \ {\ xrightarrow {}} \ Na_ {4} P_ {4} O_ {12} + 2CuS \ downarrow} }}

Two-stage synthesis with the formation of tetraphosphoric acid:

{\mathsf {P_{4}O_{10}+2H_{2}O\ {\xrightarrow {10^{o}C}}\ H_{4}P_{4}O_{12}}}

{\ displaystyle {\ mathsf {P_ {4} O_ {10} + 2H_ {2} O \ {\ xrightarrow {10 ^ {o} C}} \ H_ {4} P_ {4} O_ {12}}}}

followed by neutralization with sodium hydroxide :

{\mathsf {4NaOH+H_{4}P_{4}O_{12}\ {\xrightarrow {\tau ^{o}C}}\ Na_{4}P_{4}O_{12}+2H_{2}O}}

{\ displaystyle {\ mathsf {4NaOH + H_ {4} P_ {4} O_ {12} \ {\ xrightarrow {\ tau ^ {o} C}} \ Na_ {4} P_ {4} O_ {12} + 2H_ {2} O}}}

Heating of sodium dihydrogen phosphate with phosphoric acid to form sodium dihydrotetraphosphate :

{\mathsf {2NaH_{2}PO_{4}+2H_{3}PO_{4}\ {\xrightarrow {400^{o}C}}\ Na_{2}H_{2}P_{4}O_{12}+4H_{2}O}}

{\ displaystyle {\ mathsf {2NaH_ {2} PO_ {4} + 2H_ {3} PO_ {4} \ {\ xrightarrow {400 ^ {o} C}} \ Na_ {2} H_ {2} P_ {4} O_ {12} + 4H_ {2} O}}}

followed by neutralization with sodium hydroxide :

{\mathsf {Na_{2}H_{2}P_{4}O_{12}+2NaOH\ {\xrightarrow {}}\ Na_{4}P_{4}O_{12}+2H_{2}O}}

{\ displaystyle {\ mathsf {Na_ {2} H_ {2} P_ {4} O_ {12} + 2NaOH \ {\ xrightarrow {}} \ Na_ {4} P_ {4} O_ {12} + 2H_ {2} O}}}

Physical Properties

Sodium tetraphosphate forms colorless crystals.

It is soluble in water, not soluble in ethanol and acetone .

Forms crystalline hydrates of the composition Na ₄ P ₄ O ₁₂ • n H ₂ O, where n = 4 and 10.

Crystalline hydrate Na ₄ P ₄ O ₁₂ • 10H ₂ O at 40 ° C loses 6 water molecules.

In Na ₄ P ₄ O ₁₂ • 4H ₂ O crystalline hydrate, a phase transition occurs at 54 ° С, and complete dehydration occurs at 100 ° С.

Chemical Properties

Decomposes on heating:

{\mathsf {3Na_{4}P_{4}O_{12}\ {\xrightarrow {400^{o}C}}\ 4Na_{3}P_{3}O_{9}}}

{\ displaystyle {\ mathsf {3Na_ {4} P_ {4} O_ {12} \ {\ xrightarrow {400 ^ {o} C}} \ 4Na_ {3} P_ {3} O_ {9}}}}

In alkaline solutions it undergoes hydrolysis:

{\mathsf {Na_{4}P_{4}O_{12}+2NaOH\ {\xrightarrow {}}\ Na_{6}P_{4}O_{13}+H_{2}O}}

{\ displaystyle {\ mathsf {Na_ {4} P_ {4} O_ {12} + 2NaOH \ {\ xrightarrow {}} \ Na_ {6} P_ {4} O_ {13} + H_ {2} O}}}

in hot solutions, the reaction proceeds differently:

{\mathsf {Na_{4}P_{4}O_{12}+4NaOH\ {\xrightarrow {100^{o}C}}\ Na_{5}P_{3}O_{10}+Na_{3}PO_{4}+2H_{2}O}}

{\ displaystyle {\ mathsf {Na_ {4} P_ {4} O_ {12} + 4NaOH \ {\ xrightarrow {100 ^ {o} C}} \ Na_ {5} P_ {3} O_ {10} + Na_ { 3} PO_ {4} + 2H_ {2} O}}}

Literature

Chemical Encyclopedia / Editorial Board: Knunyants I.L. et al. - M .: Soviet Encyclopedia, 1992. - T. 3. - 639 p. - ISBN 5-82270-039-8 .
Chemistry Handbook / Editorial: Nikolsky B.P. et al. - 3rd ed., rev. - L .: Chemistry, 1971. - T. 2. - 1168 p.
Inorganic Synthesis Guide: 6 Vol. / Ed. Brower G. - M .: Mir, 1985 .-- T. 2 .-- 338 p.