Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Potassium Phosphate, Monobasic (Potassium Dihydrogen Phosphate)
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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 Potassium 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, Loss on Drying, Chloride, Sulfate, Heavy Metals, Iron, and Sodium.
KH2PO4
Formula Wt 136.08
CAS No. 7778-77-0
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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white or colorless solid buffer solutions melting point, 253 °C 33 g in 100 mL at 25 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.0% KH2PO4 pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 4.1–4.5 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.01% Loss on drying . . . . . . . . . . . . . . . . . . . . . . 0.2% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.003% Heavy metals (by ICP–OES) . . . . . . . . . . . . . . 0.001% Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.002% Sodium (Na) . . . . . . . . . . . . . . . . . . . . . . . . 0.005%
© 2017 American Chemical Society
A
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4305 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By acid–base titrimetry). Weigh accurately about 5.0 g of sample, and dissolve in 50 mL of water. Titrate with 1 N sodium hydroxide volumetric solution to the inflection point at about pH 8.8, as measured with a pH meter. One milliliter of 1 N sodium hydroxide corresponds to 0.1361 g of KH2PO4.
pH of a 5% Solution at 25.0 °C Downloaded by CORNELL UNIV on June 12, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4305
[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]. Dissolve 10 g in 100 mL of water.
Loss on Drying Weigh accurately about 2 g, and dry for 2 h at 105 °C.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 1.0 g of sample and 2 mL of nitric acid.
Sulfate Dissolve 2.0 g in 15 mL of water, and add 2.5 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 0.06 mg of sulfate ion (SO4) in 20 mL of water, and add 1.0 mL of (1:19) hydrochloric acid. Dilute both sample and control solutions to 35 mL with water, add 5.0 mL of 40% barium chloride solution to each, and mix. Observe turbidity after 10 min. Sample solution turbidity should not exceed that of the control solution.
Heavy Metals ([Part 2: Trace and Ultratrace Elemental Analysis; Inductively Coupled Plasma−Optical Emission Spectroscopy (ICP–OES); Calculation of Heavy Metals (by ICP–OES) Results], by ICP–OES). Use 1.0 g sample.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 2 (Hydroxylamine and 1,10-Phenanthroline)]. Dissolve 1.0 g in water, dilute with water to 20 mL, and use 10 mL.
Sodium (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).
© 2017 American Chemical Society
B
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4305 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
For the Determination of Sodium
S a m p l e S t o c k S o l u t i o n . Dissolve 1.0 g of sample in water, and dilute to 100 mL in a volumetric flask with water (1 mL = 0.01 g).
For the Determination of Sodium
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Na
589.0
0.20
0.01; 0.02
A/A
No
Downloaded by CORNELL UNIV on June 12, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4305
*A/A is air/acetylene.
© 2017 American Chemical Society
C
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4305 ACS Reagent Chemicals, Part 4
