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A comparative study of some hydroxyanthraquinones as acid-base indicators
J Barbosa1, E Bosch, R Carrera
1Department of Analytical Chemistry, University of Barcelona, Barcelona, Spain.
Talanta
|November 1, 1985
Summary
Four anthraquinone dyes, including Alizarin and Alizarin S, were evaluated as acid-base indicators. They demonstrated good performance, comparable to Bromocresol Green, for various titration applications.
Area of Science:
- Analytical Chemistry
- Organic Dyes
Background:
- Acid-base indicators are crucial for determining endpoints in titrations.
- Anthraquinone derivatives are known for their chromophoric properties.
Purpose of the Study:
- To compare the acid-base indicator properties of Alizarin, Alizarin S, quinizarin, and quinalizarin.
- To evaluate their performance against established indicators like Bromocresol Green and Methyl Orange.
Main Methods:
- Determination of chromaticity coordinates and complementary chromaticity coordinates.
- Measurement of pK(a) values and transition pH-ranges.
- Assessment of pH at maximum color change and optimum indicator concentration.
Main Results:
- Alizarin, Alizarin S, quinizarin, and quinalizarin were identified as effective acid-base indicators.
- The color change quality of these anthraquinone dyes was found to be similar to Bromocresol Green.
- Key parameters like pK(a) and transition pH-range were quantified for each indicator.
Conclusions:
- Anthraquinone dyes like Alizarin S show significant potential as reliable acid-base indicators.
- These indicators offer a viable alternative with comparable performance to widely used indicators in analytical titrations.
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