Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Phenolphthalein (3,3-Bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone; 3,3-Bis(phydroxyphenyl)phthalide) 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 Phenolphthalein provides, in addition to common physical constants, a general description including typical appearance, applications, change in state (approximate), aqueous solubility, density, and pKa. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Clarity of Alcohol Solution and Visual Transition Interval.
C20H14O4
Formula Wt 318.32
CAS No. 77-09-8
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . . Density . . . . . . . . . . . . . . . . pKa . . . . . . . . . . . . . . . . . .
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white or yellowish-white solid indicator for acidimetric titrations melting point, 258–262 °C almost insoluble 1.3 9.7
SPECIFICATIONS Clarity of alcohol solution . . . . . . . . . . . . . . . Passes test Visual transition interval . . . . . . . . . . . . . . . . From pH 8.0 (colorless) to pH 10 (red)
© 2017 American Chemical Society
A
DOI:10.1021/acsreagents.4265 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Clarity of Alcohol Solution Dissolve 1.0 g in 100 mL of ethyl alcohol. 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 1.0 g of potassium chloride in 100 mL of water. Adjust the pH of the solution to 8.0 (using a pH meter) with 0.01 N acid or base. Add 0.15 mL of the 1% solution reserved from the test for clarity of alcohol solution. The solution should be colorless. Titrate the solution with 0.01 N sodium hydroxide until the pH is 8.2 (using a pH meter). The solution should have a pale pink color. Continue the titration until the pH is 8.6 (using a pH meter). The solution should have a definite pink color.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4265 ACS Reagent Chemicals, Part 4
