Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Phosphorus Pentoxide (Phosphorus(V) Oxide) 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
ABSTRACT This monograph for Phosphorus Pentoxide provides, in addition to common physical constants, a general description including typical appearance, applications, 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, Insoluble Matter, Phosphorus Trioxide, Ammonium, and Heavy Metals.
P2O5
Formula Wt 141.94
CAS No. 1314-56-3
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . white to off-white, very hygroscopic solid Applications . . . . . . . . . . . . . . . . . . . . . . . . desiccant Aqueous solubility . . . . . . . . . . . . . . . . . . . . exothermic hydrolysis by water to form phosphoric acid
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥98.0% P2O5 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.02% Phosphorus trioxide (P2O3). . . . . . . . . . . . . . . Passes test Ammonium (NH4) . . . . . . . . . . . . . . . . . . . . 0.01% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 0.01%
© 2017 American Chemical Society
A
DOI:10.1021/acsreagents.4270 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Note: When making a solution, the phosphorus pentoxide must be added carefully and in small portions to water that has been cooled. Quiet dissolution may be achieved by allowing the sample to remain for at least 8 h in the uncovered weighing bottle placed in a covered beaker containing the necessary water. The pentoxide will absorb enough water from the air to dissolve without sputtering.
Assay (By acid–base titrimetry). Weigh accurately about 1.0 g, carefully dissolve in 100 mL of water, and evaporate to about 25 mL. Cool, dilute to 120 mL, add 0.5 mL of thymolphthalein indicator solution, and titrate with 1 N sodium hydroxide volumetric solution to the first appearance of a permanent blue color. One milliliter of 1 N sodium hydroxide corresponds to 0.03549 g of P2O5.
Insoluble Matter Carefully dissolve 5.0 g in 40 mL of water, warming if necessary. Filter through a tared, preconditioned filtering crucible, and set aside the filtrate for sample solution A. Wash the residue thoroughly, and dry at 105 °C.
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For the Determination of Phosphorus Trioxide, Ammonium, and Heavy Metals
S a m p l e S o l u t i o n A . Dilute the filtrate, without washings, obtained in the test for insoluble matter with water to 100 mL (1 mL = 0.05 g).
Phosphorus Trioxide† To 60 mL of sample solution A (3 g sample), add 0.20 mL of 0.1 N potassium permanganate volumetric solution. Heat to boiling, and allow to digest on a hot plate (~100 °C) for 10 min. The pink color should not be entirely discharged. (Limit about 0.02%.)
Ammonium† Dilute 2.0 mL of sample solution A (0.1 g sample) with water to 40 mL, and add 10 mL of freshly boiled 10% sodium hydroxide reagent solution and 2 mL of Nessler reagent. Any color should not exceed that produced by 0.01 mg of ammonium ion (NH4) in an equal volume of solution containing the quantities of reagents used in the test.
Heavy Metals† [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dilute 8.0 mL of sample solution A (0.4 g sample) with water to about 30 mL, boil for 5 min, cool, 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.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4270 ACS Reagent Chemicals, Part 4
