[mbas]

Hello,

For a schoolproject we needed to test the effect of saliva on the pH on some sort of drink. The only problem is we got some results that were kinda strange. Saliva would neutralize the drink, so the pH has to be closer to 7. But when we began (we even rinsed our mouths with water a few minutes before) we got with the first two drinks the opposite. For example: we used two different kind of icedtea. The pH before was: 4,08 and 3,88, and after they were (average of two results) 2,91 and 3,16. Even if the equiptment were a little bit unreliable, this is a big difference. What we did: - We rinsed our mouths with water. - We put the pH-meter in the icedtea. - We rinsed the pH-meter with water and Aqua destilate before using it again. - We drank (well not exactly drank) 15 ml of the icetea, and waited 15 seconds before we spit it out. - We put the pH meter in the icetea with salivia and waited until the pH was stable (on the pH-meter)

We did this two times (two different people drank the icedtea) with two different ice tea and with both we got this odd results. Even the pH of the two different people didn't quite differ (2,91 and 2,93 & 3,15 and 3,18). Even if our saliva was still a bit sour from the previous tea, the saliva should be above 3,88 at least. This were the drinks we started with so, we don't know what we did wrong.

Do you guys have any idea of what we did wrong? (in al the other results (were we used normal tea instead of icetea) the pH of the tea with saliva was always higher.

We would be fairy grateful if you'll find us a solution. Yours faithfully (yes, I'm going to do it the fancy way )

Two girls in desperate need of some chemistry advice

[Borek]

Bacteria?

[DrCMS]

Temperature variations?

[mbas]

The icetea was room temperature. Well maybe it could have been bacteria. We didn't wash the equiptment in the beginning.

[Arkcon]

Can you think about how much saliva a person can produce, and guess how many samples you can make before its no longer the same sort of test?  Can you think of a different way to do this test?  There's a lot of variability, trusting your mouth is the same from sample to sample.