Dibasic Sodium Phosphate USP NF Grade Specifications:
Na2HPO4-12H2O --- 358.14
Na2HPO4-7H2O --- 268.07
Na2HPO4-2H2O --- 177.99
Na2HPO4-H2O --- 159.94
Na2HPO4 --- 141.96
Phosphoric acid, disodium salt, dodecahydrate;
Disodium hydrogen phosphate, dodecahydrate CAS 10039-32-4
Phosphoric acid, disodium salt, heptahydrate;
Disodium hydrogen phosphate heptahydrate CAS 7782-85-6
Phosphoric acid, disodium salt, dihydrate;
Disodium hydrogen phosphate, dihydrate CAS 10028-24-7
Phosphoric acid, sodium salt, monohydrate;
Disodium hydrogen phosphate, monohydrate CAS [118830-14-1
Phosphoric acid, disodium salt, hydrate;
Disodium hydrogen phosphate hydrate CAS 10140-65-5
Anhydrous CAS 7558-79-4

DEFINITION
Dibasic Sodium Phosphate is dried or contains one, two, seven, or twelve molecules of water of hydration. It contains NLT 98.0% and NMT 100.5% of Na2HPO4, calculated on the dried basis.

IDENTIFICATION
A. Identification Tests-General, Sodium
B. Identification Tests-General, Phosphate.

ASSAY
Procedure
Sample: Equivalent to 2.5 g of Na2HPO4
Sample solution: Transfer the Sample to a 250-mL beaker. Add 50 mL of water and 40.0 mL of 1 N hydrochloric acid and stir until dissolved.
Blank: Transfer 40.0 mL of 1 N hydrochloric acid to a 250-mL beaker. Add 50 mL of water.
Analysis: Titrate the Blank with 1 N sodium hydroxide and record the volume of 1 N sodium hydroxide consumed. Titrate the excess acid in the Sample solution potentiometrically with 1 N sodium hydroxide to the inflection point at about pH 4, and record the burette reading. Subtract this burette reading from that of the Blank and designate the volume of 1 N sodium hydroxide resulting from this subtraction as A. Continue the titration with 1 N sodium hydroxide to the inflection point at about pH 8.8, record the burette reading, and calculate the volume (B) of 1 N sodium hydroxide required in the titration between the two inflection points (pH 4 to 8.8). Where ;A is equal to or less than B, each mL of the volume A of 1 N sodium hydroxide is equivalent to 142.0 mg of Na2HPO4. Where A is greater than B, each mL of the volume (2B - A) of 1 N sodium hydroxide is equivalent to 142.0 mg of Na2HPO4.
Acceptance criteria: 98.0% to 100.5% on the dried basis.

Specifications of Sodium Phosphate Dibasic FCC Food Grade
Disodium Monohydrogen Phosphate; Disodium Phosphate
Na2HPO4 Formula Weight, anhydrous 141.96
Na2HPO4-2H2O Formula Weight, dihydrate 177.99
INS: 339(ii) CAS: anhydrous 7558-79-4
CAS: dihydrate 10028-24-7

DESCRIPTION
Sodium Phosphate, Dibasic, occurs as a white, crystalline powder or as granules. It may be anhydrous or contain two molecules of water of hydration. The anhydrous form is hygroscopic. Both forms are freely soluble in water and insoluble in alcohol.
Function: Emulsifier; texturizer; buffer; nutrient.

REQUIREMENTS
Identification: A 1:20 aqueous solution gives positive tests for Phosphate and for Sodium.
Assay: Not less than 98.0% of Na2HPO4 after drying.
Arsenic: Not more than 3 mg/kg.
Fluoride: Not more than 0.005%.
Insoluble Substances: Not more than 0.2%.
Lead: Not more than 4 mg/kg.
Loss on Drying Anhydrous: Not more than 5.0%; Dihydrate: Between 18.0% and 22.0%.

Specifications of Sodium Phosphate Dibasic, Heptahydrate Analytical Reagent Grade
Disodium Hydrogen Phosphate Heptahydrate
Na2HPO4-7H2O
Formula Weight 268.07
CAS Number 7782-85-6

REQUIREMENTS
Assay: 98.0-102.0% Na2HPO4-7H2O
pH of a 5% solution: 8.7-9.3 at 25C

MAXIMUM ALLOWABLE
Insoluble matter: 0.005%
Chloride (Cl): 0.001%
Nitrogen compounds (as N): 0.001%
Sulfate (SO4): 0.005%
Heavy metals (as Pb): 0.001%
Iron (Fe): 0.001%

Specifications of Sodium Phosphate Dibasic Analytical Reagent Grade
Disodium Hydrogen Phosphate
(suitable for buffer solutions)
Na2HPO4
Formula Weight 141.96
CAS Number 7558-79-4

REQUIREMENTS
Assay: 99.0% Na2HPO4 min
pH of a 5% solution: 8.7-9.3 at 25C

MAXIMUM ALLOWABLE
Insoluble matter: 0.01%
Loss on drying at 105C: 0.2%
Chloride (Cl): 0.002%
Nitrogen compounds (as N): 0.002%
Sulfate (SO4): 0.005%
Heavy metals (as Pb): 0.001%
Iron (Fe): 0.002%