Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Methyl Orange (4-(Dimethylamino)azobenzenesulfonic Acid, Sodium Salt; 4-[[4-(Dimethylamino)phenyl]azo]benzenesulfonic Acid, Sodium Salt; C.I. Acid Orange 52)
Downloaded by CORNELL UNIV on May 9, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4225
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 Methyl Orange provides, in addition to common physical constants, a general description including typical appearance, applications, 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.
C14H14N3NaO3S
Formula Wt 327.33
CAS No. 547-58-0
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . orange-yellow solid Applications . . . . . . . . . . . . . . . . . . . . . . . . pH indicator Aqueous solubility . . . . . . . . . . . . . . . . . . . . soluble in 500 parts water; more soluble in hot water
SPECIFICATIONS Clarity of solution . . . . . . . . . . . . . . . . . . . . Passes test Visual transition interval . . . . . . . . . . . . . . . . From pH 3.2 (pink) to pH 4.4 (yellow)
© 2017 American Chemical Society
A
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4225 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Clarity of Solution 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
Downloaded by CORNELL UNIV on May 9, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4225
Dissolve 1 g of potassium chloride in 100 mL of water. Adjust the pH of the solution to 3.0 (using a pH meter) with 0.01 N hydrochloric acid. Add 0.15 mL of the 0.1% solution reserved from the test for clarity of solution. The solution should have a definite pink color. Titrate the solution with 0.01 N sodium hydroxide to a pH of 3.2 (using a pH meter). A small amount of yellow color should appear, producing a pinkish orange color. Continue the titration to pH 4.4 (using a pH meter); the solution should have a definite yellow color.
© 2017 American Chemical Society
B
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4225 ACS Reagent Chemicals, Part 4
