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+ Spectrophotometry
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Muhammad Tayyab

Thymol Blue - molar absorptivity

Alison Gray  Follow

First of all, molar absorptivity is dependent on wavelength, so you either need to specify a wavelength or you need the entire spectrum.

When searching for absorptivity, it's often effective to search for the older name 'extinction coefficient'. Using that search term in Google, I found an absorption spectrum for thymol blue here (pdf).

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James Mahood  Follow
I added the wavelengths in which the experiments have been done. And also,I was not able to find the information I need in that pdf document.More
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Duncan McDougall  Follow
Its often calculated at the isobestic wavelength.More
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Eva Bentova  Follow
Just read them off the graph at Fig. 2. For the acid at 540 nm (are you sure thats the right wavelength? Its a weird wavelength to measure the acid form at) it looks like its about 0.05 L.(mol.cm)^-1, and for the base at 600 nm it looks like its about 0.85 L(mol.cm)^-1. You may want to measure that graph more precisely than my eyeball did.More
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Dr. One Two  Follow
The wavelength of choice has a maximum absorbance. The molar absorptivity is not usually calculated for other wavelengths.More
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Erica Wallace  Follow
If you use the isbestic wavelength, you only find out how much thymol blue is in the solution; you dont find out the pH of the solution, which is the purpose of using the pH indicator.More
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