Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Methylthymol Blue, Sodium Salt (3,3′-Bis[N,N-di(carboxymethyl)-aminomethyl]thymolsulfonphthalein, Sodium Salt) 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 Methylthymol Blue, Sodium Salt 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: Clarity of Solution, Suitability as a Metal Indicator, and Visual Transition Interval.
C37H40N2O13Na4S
Formula Wt 844.74
CAS No. 1945-77-3
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . green or brown solid Applications . . . . . . . . . . . . . . . . . . . . . . . . pH indicator
SPECIFICATIONS Clarity of solution . . . . . . . . . . . . . . . . . . . . Passes test Suitability as a metal indicator. . . . . . . . . . . . Passes test Visual transition interval . . . . . . . . . . . . . . . . From pH 6.5 (yellow) to pH 8.5 (blue)
TESTS Clarity of Solution Dissolve 0.1 g in 100 mL of water. Not more than a trace of turbidity or insoluble matter should remain. Reserve this solution for the test for visual transition interval.
© 2017 American Chemical Society
A
DOI:10.1021/acsreagents.4230 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Suitability as a Metal Indicator Mix 50 mL of water with 5 mL of diethylamine. Add 25–50 mg of methylthymol blue indicator mixture and 10.0 mL of 0.1 M EDTA volumetric solution. The solution is colorless or gray. Titrate with 0.1 M strontium chloride solution (described below). The color change is from colorless-gray to blue. Add 0.05 mL of 0.1 M EDTA. The color should return to the colorless-gray.
For the Determination of Suitability as a Metal Indicator
S t r o n t i u m C h l o r i d e S o l u t i o n , 0 . 1 M . Dissolve 0.666 g of strontium chloride hexahydrate in water, and dilute to 25.0 mL in a volumetric flask.
Visual Transition Interval Dissolve 1.0 g of potassium chloride in 100 mL of water. Adjust the pH of the solution to 6.5 (using a pH meter) with 0.01 N hydrochloric acid or 0.01 N sodium hydroxide. Add 0.15 mL of the 0.1% solution reserved from the test for clarity of solution. The color of solution should be yellow. Titrate the solution with 0.01 N sodium hydroxide to a pH of 8.5 (using a pH meter). The color of the solution should be blue.
© 2017 American Chemical Society
B
DOI:10.1021/acsreagents.4230 ACS Reagent Chemicals, Part 4
