Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Bromocresol Green (3′,3′′,5′,5′′-Tetrabromo-m-cresolsulfonphthalein; 4,4′-(3H-2,1-Benzoxathiol-3ylidene)bis-[(2,6-dibromo-3-methyl)phenol] S,S-Doixde)
Downloaded by CORNELL UNIV on May 16, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4061
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 Bromocresol Green 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.
C21H14Br4O5S (sultone) C21H13Br4O5SNa (sodium salt)
Formula Wt 698.02 Formula Wt 720.00
CAS No. 76-60-8 CAS No. 62625-32-5
Note: This monograph applies to both the sultone and the salt forms of this indicator.
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . white to yellow solid Applications . . . . . . . . . . . . . . . . . . . . . . . . indicator
© 2017 American Chemical Society
A
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4061 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Change in state (approximate) . . . . . . . . . . . . melting point, 218–219 °C Aqueous solubility . . . . . . . . . . . . . . . . . . . . slightly soluble
SPECIFICATIONS Clarity of solution . . . . . . . . . . . . . . . . . . . . Passes test Visual transition interval . . . . . . . . . . . . . . . . pH 3.8 (yellow) to pH 5.4 (blue)
TESTS Downloaded by CORNELL UNIV on May 16, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4061
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 3.8 (using a pH meter) with 0.01 N hydrochloric acid. 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. Titrate the solution with 0.01 N sodium hydroxide to a pH of 4.5 (using the pH meter). The color of the solution should be green. Continue the titration to a pH of 5.4. The color of the solution should be blue.
© 2017 American Chemical Society
B
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4061 ACS Reagent Chemicals, Part 4
