Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Ammonium Phosphate, Monobasic (Ammonium Dihydrogen Phosphate) 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 Ammonium Phosphate, Monobasic 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, pH of a 5% Solution at 25.0 °C, Insoluble Matter, Chloride, Nitrate, Sulfate, Heavy Metals, Iron, Calcium, Magnesium, Potassium, and Sodium.
NH4H2PO4
Formula Wt 115.03
CAS No. 7722-76-1
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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colorless solid buffer solutions melting point, 190 °C 1 g in 2.5 mL at 25 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥98.0% NH4H2PO4 pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 3.8–4.4 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.005% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 5 ppm Nitrate (NO3) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.01% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 5 ppm Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.001% Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Magnesium (Mg) . . . . . . . . . . . . . . . . . . . . . 0.0005%
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4033 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Potassium (K) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Sodium (Na) . . . . . . . . . . . . . . . . . . . . . . . . 0.005%
TESTS Assay (By acid–base titration). Weigh accurately about 2 g, and dissolve in 50 mL of water. Titrate with 1 N sodium hydroxide to the inflection point occurring at about pH 8, as measured with a pH meter. One milliliter of 1 N sodium hydroxide corresponds to 0.1150 g of NH4H2PO4.
pH of a 5% Solution at 25.0 °C [Part 2: Direct Electrometric Methods; pH Potentiometry; pH Range; Procedure for pH of a 5% Solution at 25.0 °C].
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 20.0 g dissolved in 200 mL of water.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 2.0 g of sample and 3 mL of nitric acid.
Nitrate [Part 2: Colorimetry and Turbidimetry; Nitrate; Procedure for Nitrate, Method 1 (Brucine Sulfate)]. For sample solution A, use 1.5 g. For control solution B, use 1.5 g and 1.5 mL of nitrate ion (NO3) standard solution.
Sulfate Dissolve 1.0 g in 15 mL of water, and add 2.5 mL of 10% hydrochloric acid (solution approximately pH 2). Filter through a washed filter paper, and add 10 mL of water through the same filter paper. 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 reagent 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 6.0 g in 30 mL of water. Use 25 mL to prepare the sample solution, and use the remaining 5 mL to prepare the control solution.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 2 (Hydroxylamine and 1,10-Phenanthroline)]. Use 1.0 g. Add 3 mL of dilute ammonium hydroxide (1:4) to both the sample and the standard solutions.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4033 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Calcium, Magnesium, Potassium, and Sodium (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).
For the Determination of Calcium, Magnesium, Potassium, and Sodium
S a m p l e S t o c k S o l u t i o n . Dissolve 20.0 g of sample in 75 mL of water, add 2 mL of nitric acid (1:1), transfer to a 100 mL volumetric flask, and mix (1 mL = 0.20 g).
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Ca
422.7
4.0
0.02; 0.04
N/A
No
Mg
285.2
4.0
0.01; 0.02
A/A
Yes
K
766.5
1.0
0.05; 0.10
A/A
No
Na
589.0
0.10
0.005; 0.01
A/A
No
*A/A is air/acetylene; N/A is nitrous oxide/acetylene.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4033 ACS Reagent Chemicals, Part 4
