Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Bromthymol Blue (3′,3"-Dibromothymolsulfonphthalein; 4,4′-(3H-2,1-Benzoxathiol-3-ylidene)bis-[2bromo-3-methyl-6-(1-methylethyl)phenol] S,S-Dioxide) 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 Bromthymol Blue 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: Clarity of Solution and Visual Transition Interval.
C27H28Br2O5S (sultone) C27H27Br2O5SNa (sodium salt)
Formula Wt 624.38 Formula Wt 646.37
CAS No. 76-59-5 CAS No. 34722-90-2
Note: This monograph applies to both the sultone and salt forms of this indicator.
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . cream-colored solid Applications . . . . . . . . . . . . . . . . . . . . . . . . indicator
© 2017 American Chemical Society
A
DOI:10.1021/acsreagents.4064 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Change in state (approximate) . . . . . . . . . . . . melting point, 200–202 °C Aqueous solubility . . . . . . . . . . . . . . . . . . . . sparingly soluble
SPECIFICATIONS Clarity of solution . . . . . . . . . . . . . . . . . . . . Passes test Visual transition interval . . . . . . . . . . . . . . . . pH 6.0 (yellow) to pH 7.6 (blue)
TESTS Clarity of Solution If the indicator is the sultone form, dissolve 0.1 g in 100 mL of alcohol. If the indicator is a salt form, dissolve 0.1 g in 100 mL of water. Not more than a faint trace of turbidity or insoluble matter should remain. Reserve the solution for the test for visual transition interval.
Visual Transition Interval Dissolve 1 g of potassium chloride in 100 mL of water. Adjust the pH of the solution to 6.0 (using a pH meter as described) with 0.01 N hydrochloric acid or sodium hydroxide. Add 0.10–0.30 mL of the 0.1% solution reserved from the test for clarity of solution. The color of the solution should be yellow, with not more than a faint trace of green color. Titrate the solution with 0.01 N sodium hydroxide to a pH of 6.7 (using a pH meter). The color of the solution should be green. Continue the titration to pH 7.6. The color of the solution should be blue.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4064 ACS Reagent Chemicals, Part 4
