Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Sulfurous Acid 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 Sulfurous Acid provides, in addition to common physical constants, a general description including typical appearance, applications, density, and pKa. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, Residue after Ignition, Chloride, Heavy Metals, and Iron.
(a solution of SO2 in water)
CAS No. 7782-99-2
GENERAL DESCRIPTION Typical appearance Applications . . . . . Density . . . . . . . . pKa . . . . . . . . . .
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colorless, clear liquid reducing agent 1.03 1.8
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥6.0% SO2 Maximum Allowable Residue after ignition. . . . . . . . . . . . . . . . . . 0.005% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 5 ppm Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 2 ppm Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ppm
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4390 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By iodometric titration). Tare a glass-stoppered conical flask containing 50.0 mL of 0.1 N iodine. Quickly introduce about 2 mL of the sample, stopper, and weigh again. Titrate the excess iodine with 0.1 N sodium thiosulfate volumetric solution, adding 3 mL of starch indicator solution near the end of the titration. One milliliter of 0.1 N iodine consumed corresponds to 0.003203 g of SO2.
Residue after Ignition Evaporate 20.0 g (20 mL) to dryness on a hot plate (~100 °C) in a tared, preconditioned crucible or dish, and ignite at 800 ± 25 °C for 15 min.
Chloride Digest 10.0 g (10 mL) with 2 mL of nitric acid on a hot plate (~100 °C) for 1 h. Cool, and dilute with water to 100 mL. To 20 mL of the solution, 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.
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. To 10.0 g (10 mL) add 10 mL of water, boil to expel the sulfur dioxide, and dilute with water to 25 mL.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. To 2.0 g (2.0 mL), add about 10 mg of sodium carbonate, and evaporate to dryness. Dissolve the residue with 0.5 mL of hydrochloric acid, add 0.5 mL of nitric acid, and evaporate again to dryness. Dissolve the residue in 2 mL of hydrochloric acid, dilute with water to 50 mL, and use the solution without further acidification.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4390 ACS Reagent Chemicals, Part 4
