Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Potassium Nitrate 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 Nitrate 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, Iodate, Nitrite, Phosphate, Sulfate, Heavy Metals, Iron, Calcium, Magnesium, and Sodium.
KNO3
Formula Wt 101.10
CAS No. 7757-79-1
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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white solid preparation of standard solutions melting point, 334 °C 32 g in 100 mL at 20 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.0% KNO3 pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 4.5–8.5
Insoluble matter . . . . . . . Chloride (Cl) . . . . . . . . . Iodate (IO3) . . . . . . . . . . Nitrite (NO2) . . . . . . . . . Phosphate (PO4) . . . . . . . Sulfate (SO4) . . . . . . . . . Heavy metals (by ICP–OES)
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© 2017 American Chemical Society
Maximum Allowable 0.005% 0.002% 5 ppm 0.001% 5 ppm 0.003% 5 ppm
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DOI:10.1021/acsreagents.4296 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Iron (Fe) . . . . . Calcium (Ca) . . Magnesium (Mg) Sodium (Na) . . .
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3 ppm 0.005% 0.002% 0.005%
TESTS Assay (By acid–base titrimetry). Weigh, to the nearest 0.1 mg, about 0.4 g of sample, and dissolve in 100 mL of water. Pass the solution through a cation-exchange column [Part 2: Titrimetric Methods; Ion-Exchange Column Assays; Method for IonExchange Column Assays] with water at a rate of about 5 mL/min, and collect the eluate in a 500 mL titration flask. Then, wash the resin in a column at a rate of about 10 mL/min, and collect in the same titration flask. Add 0.15 mL of phenolphthalein to the flask, and titrate with 0.1 N sodium hydroxide. Continue the titration as the washing proceeds until 50 mL of the eluate requires no further titration. One milliliter of 0.1 N sodium hydroxide corresponds to 0.01011 g of KNO3.
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 g dissolved in 150 mL of water.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 0.50 g.
Iodate [Part 2: Direct Electrometric Methods; Specific Polarographic Procedures; Polarographic Procedure for Bromate and Iodate]. Use 10.0 g of sample in 25 mL of solution. For the standard, add 0.05 mg of iodate ion (IO3).
Nitrite [Part 2: Direct Electrometric Methods; Specific Polarographic Procedures; Polarographic Procedure for Nitrate]. Use 1.0 g of sample and 0.01 mg of nitrite.
Phosphate [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 1 (Direct Molybdenum Blue)]. Dissolve 4.0 g in 25 mL of approximately 0.5 N sulfuric acid, and continue as directed.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4296 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Sulfate [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 2]. Evaporate 1.7 g using 7 mL of dilute hydrochloric acid (1:1). Repeat the evaporation, and heat the last residue for 1 h at 120 °C.
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 2.0 g sample.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Use 3.3 g.
Calcium, Magnesium, 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, and Sodium
S a m p l e S t o c k S o l u t i o n . Dissolve 5.0 g of sample in water in a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.05 g).
For the Determination of Calcium, Magnesium, and Sodium
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Ca
422.7
0.50
0.025; 0.05
N/A
No
Mg
285.2
0.50
0.01; 0.02
A/A
Yes
Na
589.0
0.20
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.4296 ACS Reagent Chemicals, Part 4
