Science Buddies: "Ask an Expert"

We are asked to come up with a device that can measure pH levels, the problem is that some devices are too expensive and we need it tomorrow. Do you have any suggestions on what we can use aside from pH paper? ThankS

Hi Klonoa,

You are probably interested in pH indicators. With this method, you add a few drops of the indicator to the solution you're interested in, and it changes color depending on the pH. Each one will tell you if the solution is above or below a certain range, so to investigate a completely unknown solution, you'd need several indicators, and you'd want to divide your sample into as many parts as you have indicators -- some of them are alkaline or acidic and you wouldn't want that to interfere with your measurement. Plenty of info about specific indicators available by googling.

Can you tell us more about the project you're planning?

Good luck,
Amanda

Hi,

To measure ph you need look no farther than your kitchen or garden. Here are some ideas:

http://www.woodrow.org/teachers/chemist ... exp23.html

Red cabbage is particularly good because its color changes occur over a wide ph range.

http://www.pharmainfo.net/reviews/natur ... ors-review

(be sure to scroll down the page of the second site to see the interesting info)

http://antoine.frostburg.edu/chem/senes ... tors.shtml

Good luck!

Barrett Tomlinson

Thank you for your ideas. It really helped me a lot. My project is about the "Comparison of pH levels in mouths of mammals in a specific period of time" There are actually many factors that affect it like high sugar diet. Using mouthwash or similar products may also increase saliva pH.

We really needed a device that is reliable and accurate. So again thank you for your suggestions
Barrett Tomlinson
Amanda

Long before modern pH meters were available in laboratories, pH was accurately measured using titration methods and phenolphthalein which switches from clear to pink at a pH of about 8.2. See http://en.wikipedia.org/wiki/Titration Obviously, a modern pH meter significantly decreases the labor costs; however, the older methods still work and are as accurate as titrator (person doing the work).