Science Buddies: "Ask an Expert"

Hi im doing my science fair product and i need to develop it, how do i look or measure soap residuals in water? Which are the easiers residuals to look for? is it hard to find a ph meter and meaure the ph of water after the soap has make contact?

Hi EstherCast,

Soapy water has a pH greater than 7 while tap water has a pH close to 7. Depending on how you are making your tests, you may be able to use pH to detect soap residual. For example, the following link describes a procedure for determining if glassware has been rinsed enough to remove any soap residual.

https://www.alconox.com/downloads/pdf/cap.pdf

It’s fairly easy to use a pH meter for water testing. If your school has a pH meter you might want to ask your teacher about using it for your project. If not, you might be able to use pH test strips or a simple pH tester. Neither of these are as accurate as a pH meter but they are less expensive and may be OK for your project.

You may want to post some additional information about your project and the experiment you are planning. With more details the forum contributors should be able to provide more helpful answers to your questions.

I hope this helps. Please post again if you have more questions.

A. Norman

Thanks