Bromine - ACS Reagent Chemicals (ACS Publications)

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

Bromine 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

Downloaded by CORNELL UNIV on May 12, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4060

ABSTRACT This monograph for Bromine 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, Residue after Evaporation, Chlorine, Iodine, Sulfur Compounds, Heavy Metals, and Nickel.

Br2

Formula Wt 159.81

CAS No. 7726-95-6

GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .

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dark reddish-brown fuming liquid brominating agent boiling point, 60 °C 3.13 g in 100 mL at 30 °C

SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.5% Br2 Maximum Allowable Residue after evaporation . . . . . . . . . . . . . . . 0.005% Chlorine (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.05% Iodine (I) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.001% Sulfur compounds (as S) . . . . . . . . . . . . . . . . 0.001% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 2 ppm Nickel (Ni) . . . . . . . . . . . . . . . . . . . . . . . . . 5 ppm

© 2017 American Chemical Society

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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.

DOI:10.1021/acsreagents.4060 ACS Reagent Chemicals, Part 4

ACS Reagent Chemicals

Monograph

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

TESTS Assay


(By iodometric titration). Weigh a 250 mL volumetric flask containing 15 g of potassium iodide in 45 mL of water. Add 1 mL of sample. Stopper promptly, mix by shaking, and reweigh. Dilute to volume with water, and mix thoroughly. Place a 25.0 mL aliquot of this solution in a conical flask, and titrate the liberated 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 sodium thiosulfate corresponds to 0.007990 g of Br2.

Residue after Evaporation [Part 2: Gravimetric Methods; Residue after Evaporation]. In a fume hood, evaporate 31 g (10 mL) to dryness from a tared, preconditioned container on a hot plate (~100 °C), and dry the residue at 105 °C for 30 min. Reserve the residue for the test for heavy metals.

Chlorine To each of two 250 mL wide-mouth conical flasks, add 0.5 mL of dilute sulfuric acid (1:4), 5 mL of potassium bromide solution (1.50 g of KBr per liter), and 35 mL of water. For the sample, add 3 g (1.0 mL) of the bromine to one of the flasks. For the standard, add 1.5 mg of chloride ion (3.2 mg of KCl) to the other. Digest each on a hot plate (~100 °C) until the sample solution is colorless, to each add 4 mL of potassium peroxydisulfate solution (1.0 g per 100 mL), and wash down the sides of the flasks with a little water. Digest again on a hot plate (~100 °C) for 30–40 min. Cool and dilute each with water to 100 mL. Transfer 1.0 mL of each solution into separate 50 mL beakers, and add 22 mL of water, 1 mL of nitric acid, and 1 mL of silver nitrate reagent solution to each. Any turbidity in the solution of the sample should not exceed that in the standard.

Iodine To each of two 250 mL wide-mouth conical flasks, add 1.0 mL of 10% potassium chloride reagent solution, 50 mL of water, and a few silicon carbide boiling chips. For the sample, add 10.5 g (3.5 mL) of the bromine to one of the flasks. For the control, add 0.3 mL of the bromine and 0.1 mg of iodide ion (0.13 mg of KI) to the other flask. Boil cautiously in a hood to remove the excess bromine, adding water as required to maintain a volume of not less than 50 mL. When no trace of yellow color remains in either flask, cool, and add 5 mL of 10% potassium iodide reagent solution and 5 mL of dilute sulfuric acid (1:4) to each. Any color in the solution of the sample should not exceed that in the control.

Sulfur Compounds To 8 g (2.6 mL), add 5 mL of water, and evaporate to dryness on a hot plate (~100 °C). To the residue, add 5 mL of dilute hydrochloric acid (1:19), filter if necessary, and dilute to 50 mL with water. To 10 mL of this residue solution, add 1 mL of 12% barium chloride reagent solution. Any turbidity should not exceed that produced by 0.05 mg of sulfate ion (SO4) in an equal volume of solution containing the quantities of reagents used in the test. Compare 10 min after adding the barium chloride to the sample and standard solutions. Reserve the remaining residue solution for the test for nickel.

Heavy Metals For the sample, use the residue reserved from the test for residue after evaporation. For the standard, use a solution containing 0.06 mg of lead. To each, add 3 mL of nitric acid, 1 mL of water, and 1.0 mL of 1% sodium carbonate reagent solution. Evaporate to dryness on a hot plate (~100 °C), dissolve the residues in about 20 mL of water, and dilute with water to 25 mL. Adjust the pH of the standard and sample solutions to between 3 and 4 (using a pH meter) with 1 N acetic acid reagent solution or 10% ammonium hydroxide reagent solution, dilute with water to 40 mL, and mix. Add 10 mL of freshly


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ACS Reagent Chemicals

Monograph

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

prepared hydrogen sulfide water to each, and mix. Any color in the solution of the sample should not exceed that in the standard.

Nickel


To 25 mL of the residue solution reserved from the test for sulfur compounds, add 5 mL of bromine water. Stir, and add ammonium hydroxide (1:1) until the bromine color is discharged. Add 5 mL of 1% dimethylglyoxime reagent solution in ethyl alcohol and 5 mL of 10% sodium hydroxide reagent solution. Any red color should not exceed that produced by 0.02 mg of nickel ion (Ni) in an equal volume of solution containing the quantities of reagents used in the test. Compare 10 min after adding the dimethylglyoxime to the sample and standard solutions.


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Bromine - ACS Reagent Chemicals (ACS Publications)

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