Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Potassium Nitrite 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 Nitrite 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, Insoluble Matter, Chloride, Sulfate, Heavy Metals, Iron, Calcium, Magnesium, and Sodium.
KNO2
Formula Wt 85.10
CAS No. 7758-09-0
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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white or slightly yellow solid complexing agent melting point, 441 °C; decomposition starts at 350 °C 300 g in 100 mL at 20 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥96.0% KNO2
Insoluble matter . . . Chloride (Cl) . . . . . Sulfate (SO4) . . . . . Heavy metals (as Pb) Iron (Fe) . . . . . . . . Calcium (Ca) . . . . . Magnesium (Mg) . . . Sodium (Na) . . . . . .
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© 2017 American Chemical Society
Maximum Allowable 0.01% 0.03% 0.01% 0.001% 0.001% 0.005% 0.002% 0.5%
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DOI:10.1021/acsreagents.4297 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By oxidation–reduction titrimetry). Weigh accurately about 6 g, dissolve in water, and dilute with water to 1 L in a volumetric flask. Add 5 mL of sulfuric acid to 300 mL of water, and while the solution is still warm, add 0.1 N potassium permanganate volumetric solution until a faint pink color that persists for 2 min is produced. Then, add 40.0 mL of 0.1 N potassium permanganate, and mix gently. Add, slowly and with constant agitation, 25.0 mL of the sample solution, holding the tip of the pipette well below the surface of the liquid. Add 15.0 mL of 0.1 N ferrous ammonium sulfate volumetric solution, allow the solution to stand for 5 min, and titrate the excess of ferrous ammonium sulfate with 0.1 N potassium permanganate. Each milliliter of 0.1 N potassium permanganate consumed by the potassium nitrite corresponds to 0.004255 g of KNO2.
where V = the volume, in mL, of potassium permanganate used in the back-titration.
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 20 g dissolved in 200 mL of water.
Chloride Dissolve 3.3 g in 20 mL of water, filter if necessary through a chloride-free filter, and dilute with water to 100 mL. Dilute 1.0 mL of this solution with 15 mL of water, and slowly add 1 mL of acetic acid. Heat to boiling, boil gently for 5 min, cool, and dilute with water to 20 mL. Add 1 mL of nitric acid and 1 mL of silver nitrate reagent solution. Any turbidity should not exceed that produced by 0.01 mg of chloride ion (Cl) in an equal volume of solution containing the quantities of reagents used in the test.
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For the Determination of Sulfate, Heavy Metals, and Iron
S a m p l e S o l u t i o n A . Dissolve 10.0 g in water, and dilute with water to 100 mL (1 mL = 0.1 g).
Sulfate† [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 2]. Use 5.0 mL of sample solution A (0.5 g sample) plus 1 mL of hydrochloric acid.
Heavy Metals† [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. To 30 mL of sample solution A (3 g sample), add 5 mL of hydrochloric acid, and evaporate to dryness on a hot plate (~100 °C). Add 5 mL of hydrochloric acid, and again evaporate to dryness. Dissolve in about 20 mL of water, and dilute with water to 25 mL. For the control, add 0.02 mg of lead to 10 mL of sample solution A (1 g sample), add 5 mL of hydrochloric acid, and treat exactly as the 30 mL of sample solution A.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4297 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Iron
†
[Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. To 10 mL of sample solution A (1 g sample), add 5 mL of hydrochloric acid, and evaporate to dryness on a hot plate (~100 °C). Dissolve the residue in 15–20 mL of water, add 2 mL of hydrochloric acid, filter if necessary, and dilute with water to 50 mL. Use the solution without further acidification.
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 A . Dissolve 0.40 g of sample in water in a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.004 g). S a m p l e S t o c k S o l u t i o n B . Dissolve 5.0 g of sample in 80 mL of water. Transfer to 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
0.004
0.01; 0.02
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.4297 ACS Reagent Chemicals, Part 4
