Hi. The objective is to demonstrate to students that surfactant solutions can solubilize dirt/hydrophobic substances. So, I am looking for dyes/any material which can show visible change in color when surfactant is added to water. Please let me know if you have any suggestions. thanks in advance.
Dear Abhinav:
In the attached article, you can find the desired dye and theory.
Regards
You might also like to look at the fascinating Reichardt's dye.(Google it!). It shows huge colour changes when dissolved in different solvents and micelles.
Some tests are specific to certain types of surfactants. For example, Methylene Blue active substance or MBAS testing is a colorimetric analysis test method that uses methylene blue as a cationic dye, to detect quantities of anionic surfactants. There are test kits available for simplicity from companies such as: CHEMetrics, HACH and Osprey.
One other simple way of showing solubilization of dirt by soaps and detergents is to simply dissolve an oil soluble dye in vegetable oil, place a couple of grams of this solution in a beaker, add water on top mix, let settle, no color in the water will develop. Then pour water+surfactant on top of the colored oil, mix and let settle. The surf solution will suspend the oil and the liquid will remain colored.
Dear Abhinav,
it would be a more direct visualization of you finely disperse e.g. a small amount of diesel in water by sonication. Then adding drops of dish washing agent until turbidity disappears. Alternatively you may shake a very small amount of diesel in water and for comparison with a concentrated surfactant solution. You have to make sure that amount of oil is below solubilization capacity because otherwise emulsions will be formed.
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