Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Potassium Oxalate Monohydrate (Oxalic Acid, Potassium Salt, Monohydrate) 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 Oxalate Monohydrate 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, Substances Darkened by Hot Sulfuric Acid, Neutrality, Insoluble Matter, Chloride, Sulfate, Ammonium, Heavy Metals, Iron, and Sodium.
(COOK)2•H2O
Formula Wt 184.23
CAS No. 6487-48-5
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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colorless solid reducing agent dehydrates at 100 °C 36 in 100 mL at 20 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98.5–101.0% K2C2O4 · H2O Substances darkened by hot sulfuric acid . . . . . Passes test Neutrality . . . . . . . . . . . . . . . . . . . . . . . . . Passes test Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.01% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.002% Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.01% Ammonium (NH4) . . . . . . . . . . . . . . . . . . . . 0.002% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 0.002% Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.001% Sodium (Na) . . . . . . . . . . . . . . . . . . . . . . . . 0.02%
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4298 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 1.8 g, and dissolve in water in a 250 mL volumetric flask. Dilute to volume, and mix. To a 50 mL aliquot, add 50 mL of water and 5 mL of sulfuric acid. Titrate slowly with 0.1 N potassium permanganate volumetric solution until about 25 mL has been added. Heat the solution to about 70 °C, and complete the titration to a permanent faint pink color. One milliliter of 0.1 N potassium permanganate consumed corresponds to 0.009212 g of K2C2O4 · H2O.
Substances Darkened by Hot Sulfuric Acid Heat 1.0 g in a recently ignited test tube with 10 mL of sulfuric acid until the appearance of dense fumes. The acid when cooled should have no more color than a mixture of the following composition: 0.2 mL of cobalt chloride reagent solution, 0.3 mL of ferric chloride reagent solution, 0.3 mL of cupric sulfate reagent solution, and 9.2 mL of water.
Neutrality Dissolve 2.0 g in 200 mL of water, and add 10.0 mL of 0.01 N oxalic acid and 0.20 mL of 1% phenolphthalein indicator solution. Boil the solution in a flask for 10 min, passing through it a stream of carbon dioxide-free air. Cool the solution rapidly to room temperature while keeping the flow of carbon dioxide-free air passing through it, and titrate with 0.01 N sodium hydroxide. Not less than 9.2 nor more than 10.5 mL of 0.01 N sodium hydroxide should be required to match the pink color produced in a buffer solution containing 0.20 mL of 1% phenolphthalein indicator solution. The buffer solution contains: 3.1 g of boric acid, 3.8 g of potassium chloride, and 5.90 mL of 1 N sodium hydroxide in 1 L of water.
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 10 g dissolved in 100 mL of water.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Dissolve 2.0 g in water plus 10 mL of nitric acid, filter if necessary through a chloride-free filter, and dilute with water to 100 mL. To 25 mL of the solution, add 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.
Sulfate [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 4].
Ammonium Dissolve 1.0 g in 50 mL of ammonia-free water, and add 2 mL of Nessler reagent. Any color should not exceed that produced by 0.02 mg of ammonium ion (NH4) in an equal volume of solution containing 2 mL of Nessler reagent.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4298 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Mix 2.0 g with 2 mL of water, add 2 mL of nitric acid and 2 mL of 30% hydrogen peroxide, and digest in a covered beaker on a hot plate (~100 °C) until reaction ceases. Remove the cover, and evaporate to dryness. Dissolve the residue in 4 mL of dilute nitric acid (1:1), and again evaporate to dryness. Dissolve the residue in about 20 mL of water, dilute with water to 32 mL, and use 24 mL to prepare the sample solution. Use the remaining 8.0 mL, plus the residue from evaporation of 1 mL of 30% hydrogen peroxide and 3 mL of nitric acid to dryness, to prepare the control solution.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Mix 2.0 g with 2 mL of water, add 2 mL of nitric acid and 2 mL of 30% hydrogen peroxide, and digest in a covered beaker on a hot plate (~100 °C) until reaction ceases. Remove the cover, and evaporate to dryness. Add 5 mL of hydrochloric acid, and again evaporate to dryness. Dissolve the residue in a few milliliters of water, add 4 mL of hydrochloric acid, and dilute with water to 100 mL. Use 50 mL without further acidification. For the control, use the residue from evaporating to dryness 1 mL of nitric acid, 1 mL of 30% hydrogen peroxide, and 2.5 mL of hydrochloric acid.
Sodium (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).
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
0.05
0.01; 0.02
A/A
No
*A/A is air/acetylene.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4298 ACS Reagent Chemicals, Part 4
