Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Sulfuric Acid, Fuming 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 Sulfuric Acid, Fuming provides, in addition to common physical constants, a general description including typical appearance, applications, aqueous solubility, 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, Nitrate, Ammonium, Arsenic, and Iron.
CAS No. 8014-95-7
Note: This specification applies to fuming sulfuric acid with nominal contents of 15%, 20%, or 30% free SO3.
GENERAL DESCRIPTION Typical appearance Applications . . . . . Aqueous solubility . pKa . . . . . . . . . .
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colorless to light-brown viscous liquid dehydrating agent miscible; generates heat ~ –3
SPECIFICATIONS Assay (free SO3) . . . . . . . . . . . . . . . . . . . . . 12.0–17.0%, 18.0–24.0%, or 26.0–29.5% Maximum Allowable Residue after ignition. . . . . . . . . . . . . . . . . . 0.002% Nitrate (NO3) . . . . . . . . . . . . . . . . . . . . . . . 1 ppm Ammonium (NH4) . . . . . . . . . . . . . . . . . . . . 3 ppm Arsenic (As) . . . . . . . . . . . . . . . . . . . . . . . . 0.03 ppm Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 2 ppm
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4388 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By acid–base titrimetry). Weigh accurately about 4.0 g in a tared Dely weighing tube. Carefully transfer to a casserole containing 100 mL of carbon dioxide-free water by placing the tip of the tube beneath the surface and flushing the tube with carbon dioxide-free water. Cool, add 0.15 mL of phenolphthalein indicator solution, and titrate with 1 N sodium hydroxide volumetric solution. One milliliter of 1 N sodium hydroxide corresponds to 0.04904 g of H2SO4.
where % free SO3 = 4.445 × (% H2SO4 – 100). Note: For accurate results, a weight burette should be used. The Dely weighing tube and its use are described in standard reference books.
Residue after Ignition [Part 2: Gravimetric Methods; Residue after Ignition]. Evaporate 50.0 g (27 mL) to dryness in a tared, preconditioned platinum dish, and ignite at 800 ± 25 °C for 15 min.
Nitrate [Part 2: Colorimetry and Turbidimetry; Nitrate; Procedure for Nitrate, Method 1 (Brucine Sulfate)].
For the Determination of Nitrate
S a m p l e S o l u t i o n A . Cautiously add 10.0 g (5 mL) to 1.0 mL of water, dilute to 50 mL with brucine sulfate reagent solution, and mix. C o n t r o l S o l u t i o n B . Cautiously add 10.0 g (5 mL) to 1.0 mL of nitrate ion (NO3) standard solution, dilute to 50 mL with brucine sulfate reagent solution, and mix.
Continue with the procedure, starting with the preparation of blank solution C.
Ammonium Add 1.5 g (0.8 mL) of sample to 25 mL of cold water. Cautiously add 20 mL of freshly boiled 10% sodium hydroxide solution while cooling the solution. Transfer to a 50 mL Nessler tube, add 2 mL of Nessler reagent, and dilute to volume with water. The color produced should not exceed that produced by 0.005 mg of ammonium ion treated identically.
Arsenic [Part 2: Colorimetry and Turbidimetry; Arsenic]. To 100.0 g (52 mL), add 3 mL of nitric acid, and evaporate on a hot plate (~100 °C) to about 10 mL. Cool, cautiously dilute with about 20 mL of water, and evaporate to about 5 mL. Cool, cautiously dilute again with about 20 mL of water, and evaporate just to dense fumes of sulfur trioxide. Cool, and cautiously wash the solution into a generator flask with the aid of 50 mL of water. Omit the addition of 20 mL of dilute sulfuric acid (1:4). For the standard, use 0.003 mg of arsenic ion (As).
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4388 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)]. Cautiously add 5.0 g (2.6 mL) to about 10 mg of sodium carbonate, and evaporate to dryness by heating on a hot plate (~100 °C). Cool, add 5 mL of dilute hydrochloric acid (1:1), cover with a watch glass, and digest on a hot plate (~100 °C) for 15 min. Cool, and dilute with water to 25 mL.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4388 ACS Reagent Chemicals, Part 4
