Sodium Oxalate - ACS Publications - American Chemical Society

Monograph pubs.acs.org/doi/book/10.1021/acsreagents

Sodium Oxalate (Ethanedioic Acid, Disodium Salt) 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 Sodium Oxalate provides, in addition to common physical constants, a general description including typical appearance, applications, 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, Loss on Drying, Neutrality, Chloride, Ammonium, Sulfate, Heavy Metals, Iron, Potassium, and Substances Darkened by Hot Sulfuric Acid.

(COONa)2

Formula Wt 134.00

CAS No. 62-76-0

GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . white solid Applications . . . . . . . . . . . . . . . . . . . . . . . . standardizing potassium and permanganate solutions; titrimetry Aqueous solubility . . . . . . . . . . . . . . . . . . . . 3.7 g in 100 mL at 20 °C

SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.5% (COONa)2 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.005% Loss on drying . . . . . . . . . . . . . . . . . . . . . . 0.01% Neutrality . . . . . . . . . . . . . . . . . . . . . . . . . Passes test Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.002% Ammonium (NH4) . . . . . . . . . . . . . . . . . . . . 0.002% Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.002% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 0.002% Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.001% Potassium (K) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Substances darkened by hot sulfuric acid . . . . . Passes test

© 2017 American Chemical Society

A

DOI:10.1021/acsreagents.4359 ACS Reagent Chemicals, Part 4

ACS Reagent Chemicals

Monograph

pubs.acs.org/doi/book/10.1021/acsreagents

TESTS Assay (By indirect titration of reducing power of oxalate against permanganate). Weigh, to the nearest 0.1 mg, about 0.25 g of the dried sample, and dissolve with 100 mL of water in a 250 mL glass-stoppered flask. Add 3 mL of sulfuric acid, and then slowly add 20 mL of 0.1 N potassium permanganate volumetric solution. Heat the solution to 70 °C, and complete the titration with the permanganate until a pale pink color persists for 30 s. One milliliter of 0.1 N potassium permanganate corresponds to 0.0067 grams of Na2C2O4.

Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 20 g dissolved in 500 mL of water.

Loss on Drying Weigh accurately 10 g in a tared, preconditioned dish or crucible, and dry at 105 °C to constant weight.

Neutrality Dissolve 2.0 g in 200 mL of water, and add 10.0 mL of 0.01 N oxalic acid and 0.15 mL of 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. 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 of a buffer solution containing 0.15 mL of phenolphthalein indicator solution. For the buffer solution, add 3.1 g of boric acid, 3.8 g of potassium chloride, and 5.90 mL of 1 N sodium hydroxide to a 1 L container, and fill to the mark with water.

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.

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. †

For the Determination of Sulfate, Heavy Metals, and Iron

S a m p l e S t o c k S o l u t i o n A . In a 400 mL beaker, mix 10.0 g of sample with 50 mL of water. Add 5.0 mL of 1% sodium carbonate reagent solution, 15 mL of nitric acid, and 15 mL of 30% hydrogen peroxide. Digest in a covered beaker on a hot plate until the reaction ceases. Remove the cover, and evaporate to dryness. Add 25 mL of dilute hydrochloric acid (1:1), and evaporate to dryness. Repeat the evaporation with another 25 mL of dilute hydrochloric acid (1:1). Dissolve the residue in 30 mL of water, add 1 mL of dilute hydrochloric acid (1:9), filter, and dilute to 60 mL with water (1.0 g = 6.0 mL).


B



Monograph


B l a n k S o l u t i o n B . In a 400 mL beaker, add 10 mL of 1% sodium carbonate reagent solution to 30 mL of nitric acid and 30 mL of 30% hydrogen peroxide, and evaporate to dryness. Add 100 mL of dilute hydrochloric acid (1:1), and evaporate to dryness. Dissolve the residue in 30 mL of water, add 2 mL of dilute hydrochloric acid (1:19), filter, and dilute to 120 mL with water.

Sulfate† [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 1]. For the sample, use 30 mL (5 g sample) of sample stock solution A. Prepare standards using 30 mL of blank solution B and 0.05 and 0.10 mg of sulfate ion (SO4), respectively.

Heavy Metals† [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. For the sample, use 9 mL (1.5 g sample) of sample stock solution A. Prepare standards by adding 0.01 and 0.02 mg lead ion (Pb) to, respectively, 3 mL (0.5 g sample) of sample stock solution A and 6 mL of blank solution B. Adjust the pH of the standard and sample solutions to between 3 and 4 (using a pH meter) with 1 N acetic acid or 10% ammonium hydroxide reagent solution, dilute with water to 40 mL, and mix. Add 5 mL of freshly prepared hydrogen sulfide water to each, and mix.

Iron† [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. For the sample, dilute 12 mL (2 g sample) of sample stock solution A to 40 mL with water. Prepare standards by adding 0.005 and 0.1 mg of iron ion (Fe), respectively, to two 12 mL portions of blank solution B, and dilute both with water to 40 mL. To the sample and standards, add 3 mL of hydrochloric acid, 30–50 mg of ammonium persulfate crystals, and 3 mL of ammonium thiocyanate reagent solution.

Potassium (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).

For the Determination of Potassium

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 5 mL of nitric acid in a 200 mL volumetric flask, and dilute to the mark with water (1 mL = 0.025 g).

For the Determination of Potassium

Element

Wavelength (nm)

Sample Wt (g)

Standard Added (mg)

Flame Type*

Background Correction

K

766.5

0.50

0.025; 0.05

A/A

No

*A/A is air/acetylene.


C



Monograph


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.


D


Sodium Oxalate - ACS Publications - American Chemical Society

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