Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Tetrabromophenolphthalein Ethyl Ester 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 Tetrabromophenolphthalein Ethyl Ester provides, in addition to common physical constants, a general description including typical appearance and applications. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, Melting Point, and Solubility.
C22H14Br4O4 (free acid) Formula Wt 661.97 C22H13Br4O4K (potassium Formula Wt 700.06 salt)
CAS No. 1176-74-5 CAS No. 62637-91-6
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . yellow to red solid Applications . . . . . . . . . . . . . . . . . . . . . . . . indicator
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥95.0% Melting point (free acid) . . . . . . . . . . . . . . . . 208.0–213.0 °C (within an interval of no more than 3.0°) Solubility. . . . . . . . . . . . . . . . . . . . . . . . . . Passes test
© 2017 American Chemical Society
A
DOI:10.1021/acsreagents.4393 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By spectrophotometry). Weigh accurately 50.0 mg, transfer to a 100 mL volumetric flask, dissolve in about 75 mL of a 50/ 50 mixture of ethyl alcohol and pH 7.00 buffer solution (described below), and dilute to volume with the mixture. Pipette 2 mL of this solution into a 100 mL volumetric flask, and dilute to volume with buffer solution. Determine the absorbance of this solution in 1.00 cm cells at the wavelength of maximum absorption, approximately 593 nm, using the pH 7.00 buffer solution as the blank. Determine the molar absorptivity by dividing the absorbance by 1.5 × 10–5 (that is, the molar concentration of the tetrabromophenolphthalein ethyl ester) and calculate the assay value as follows:
For the Assay
p H 7 . 0 0 B u f f e r S o l u t i o n . Add 291 mL of 0.1 M sodium hydroxide to 500 mL of 0.1 M monobasic potassium phosphate, and dilute with water to 1 L.
Note: Because the solutions are light-sensitive, protect them from direct light.
Melting Point [Part 2: Measurement of Physical Properties; Melting Point].
Solubility For the free acid, dissolve 0.1 g in 100 mL of toluene. For the potassium salt, dissolve 0.1 g in 100 mL of water. For either, the solution should be clear, and dissolution should be complete.
© 2017 American Chemical Society
B
DOI:10.1021/acsreagents.4393 ACS Reagent Chemicals, Part 4
