Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Sodium Phosphate, Tribasic, Dodecahydrate Part 4, Monographs for Reagent Chemicals: General Descriptions, Specifications, and Tests eISBN: 9780841230460 Tom Tyner Chair, ACS Committee on Analytical Reagents James Francis Secretary, ACS Committee on Analytical Reagents
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ABSTRACT This monograph for Sodium Phosphate, Tribasic, Dodecahydrate provides, in addition to common physical constants, a general description including typical appearance, applications, change in state (approximate), and aqueous solubility. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, Excess Alkali, Insoluble Matter, Chloride, Sulfate, Heavy Metals, and Iron.
Na3PO4 • 12H2O
Formula Wt 380.12
CAS No. 10101-89-0
Note: This reagent, when stored under ordinary conditions, may lose some water of crystallization. Any loss in water will result in an assay of more than 100% Na3PO4 · 12H2O but does not affect the determination of the relative amount of free alkali present.
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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colorless or white solid buffer; sequestering agent melting point, 75 °C soluble in 3.5 parts water, 1 part boiling water
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98.0–102.0% Na3PO4 · 12H2O Maximum Allowable Excess alkali (as NaOH). . . . . . . . . . . . . . . . . 2.5% Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.01% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.01%
© 2017 American Chemical Society
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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4366 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 0.001% Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.001%
TESTS Assay
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(By acid–base titrimetry). Weigh accurately about 7.5 g, and dissolve in 50 mL of water and exactly 50.0 mL of 1 N hydrochloric acid volumetric solution. Heat to boiling to expel carbon dioxide. While protecting the solution from absorbing carbon dioxide from the air, cool, and titrate the solution with 1 N sodium hydroxide volumetric solution to the inflection point at about pH 4, as measured with a pH meter. Calculate A, the equivalent of 1 N hydrochloric acid consumed by the sample. Continue the titration with 1 N sodium hydroxide to the second inflection point at about pH 8.8. Calculate B, the equivalent of 1 N sodium hydroxide required in the titration between the two inflection points.
If A is equal to or greater than 2B, then
If A is less than 2B, then
Excess Alkali Calculate the amount of excess alkali as sodium hydroxide from the titration values obtained in the test for assay. If A is equal to or less than 2B, there is no excess alkali present when the salt is dissolved. If A is greater than 2B, then
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Dissolve 10.0 g in 100 mL of water, add 0.10 mL of methyl red indicator solution, add hydrochloric acid until the solution is slightly acid to the methyl red indicator, and continue as described.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 1.0 g of sample and 3 mL of nitric acid.
© 2017 American Chemical Society
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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4366 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Sulfate Dissolve 1.0 g in 15 mL of water, and add 4.0 mL of 10% hydrochloric acid (solution approximately pH 2). Filter through washed filter paper, and add 10 mL of water through the same filter. For the control, add 0.10 mg of sulfate ion (SO4) in 20 mL of water, and add 1.0 mL of (1:19) hydrochloric acid. Dilute both to 35 mL with water, add 5.0 mL of 40% barium chloride solution, and mix. Observe turbidity after 10 min. Sample solution turbidity should not exceed that of the control solution.
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dissolve 4.0 g in about 20 mL of water, add 6 mL of 2 N hydrochloric acid, and dilute with water to 32 mL. Use 24 mL to prepare the sample solution, and use the remaining 8.0 mL to prepare the control solution.
Downloaded by CORNELL UNIV on May 7, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4366
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 2 (Hydroxylamine and 1,10-Phenanthroline)]. Dissolve 1.0 g in 10 mL of water, and add 3 mL of 1 N hydrochloric acid. Omit the addition of acid to the standard.
© 2017 American Chemical Society
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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4366 ACS Reagent Chemicals, Part 4
