First pKa values of some acid-base indicators

✍ Scribed by V. Das Gupta; John B. Reed Jr.

• Book ID: 102402194
• Publisher: John Wiley and Sons
• Year: 1970
• Tongue: English
• Weight: 259 KB
• Volume: 59
• Category: Article
• ISSN: 0022-3549
• DOI: 10.1002/jps.2600591136

✦ Synopsis

An attempt was made to estimate the first pKa values of bromocresol green, bromocresol purple, bromophenol blue, cresol red, and phenol red using a method similar to that of Reilley and Sawyer. Values of -0.75 (-2.13 on the Hammett acidity scale) for bromocresol purple, +1.05 for cresol red, and +1.03 for phenol red were estimated. pKa values of cresol red and phenol red were not estimated on the Hammett acidity scale, since this scale is good only for acidic solutions stronger than 0.1 M. Trials to estimate the first pKa values of bromocresol green and bromophenol blue were not successful due to the upper limitation on the strength of commercially available hydrochloric acid. Values of -0.85 (approximately -2.7 on the Hammett acidity scale) or less for bromocresol green and -0.95 (-3.2 on the Hammett acidity scale) or less for bromophenol blue have been predicted. Keyphrases Indicators, acid