Monograph pubs.acs.org/doi/book/10.1021/acsreagents
PAR (4-(2′-Pyridylazo)resorcino) 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 PAR 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 and Suitability as a Complexometric Indicator.
C11H9N3O2 (free acid) Formula Wt 215.21 C11H8N3NaO2 (monosodi- Formula Wt 237.21 um salt)
CAS No. 1141-59-9 CAS No. 16593-81-0
Note: This specification includes both the free acid and the salt forms of the indicator.
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . orange solid (free acid form) Applications . . . . . . . . . . . . . . . . . . . . . . . . complexometric indicator
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4254 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
SPECIFICATIONS Clarity of solution . . . . . . . . . . . . . . . . . . . . Passes test Suitability as a complexometric indicator (Pb) . . Passes test
TESTS Clarity of Solution If the indicator is the salt form, weigh 0.10 g of sample, and dissolve in 100 mL of water. If the indicator is the acid form, dissolve 0.10 g in 1 N sodium hydroxide volumetric solution, and dilute to 100 mL, maintaining the pH at 8.9. Not more than a trace of turbidity or insoluble matter should remain. Reserve the solution for the test for suitability as a complexometric indicator.
Suitability as a Complexometric Indicator Add 10.0 mL of 0.1 M EDTA volumetric solution to 100 mL of water. Adjust the pH of the solution to 4.0 with 1% nitric acid. Add hexamethylenetetramine reagent solution to a pH of 5–6. Add 0.2 mL of the 0.1% solution reserved from the clarity of solution test. Heat the solution to 60 °C, and titrate with 0.1 M lead nitrate volumetric solution. The color of the solution should change from yellow to pink. Add back 0.05 mL of 0.1 M EDTA. The solution should return to the original yellow color.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4254 ACS Reagent Chemicals, Part 4
