Testing the pH of common drinks using DrDAQ as a pH meter: results

The expected results shown below are the average of a poll taken at Pico before the experiment was carried out.

Liquid Expected pH Recorded pH
Milk 8 6.76
Lemon squash 4.5 3.56
Ribena 5 3.19
Cherry Coke 3 2.17
Pepsi 3 2.63
Original Coke 2.5 2.61
Black coffee 7.5 5.51
Black tea 7.5 6.37
Lemon tea 5 3.73
Apple juice 3.5 3.49
Orange juice 4 3.84
Ph Results

Graph of Expected results vs Recorded results

Warning: NEVER drink laboratory chemicals

The results here indicate that some soft drinks have a similar pH to acids. This does NOT mean that acids are safe to drink.

Answers to questions

A1. We can predict that the pH of the majority of our foods and drinks will be neutral or acidic.

A2. pH = 7.02

A3.  [H+]  = 3.5E-6 M

Background information for discussion

Dental erosion occurs when tooth enamel (and dentine) are destroyed by the action of acid on teeth. This is a different process to the damage caused by acid from decay producing bacteria.

Unlike tooth decay, erosion affects the whole surface of the tooth. Exposure to acid over a long period of time leads to progressive loss of enamel with the effect that the tooth ‘shrinks’ and crumbles at the biting edge. Eventually the dentine is exposed leading to pain and sometimes death of the tooth.

The process is irreversible and requires expensive cosmetic dentistry to restore function and appearance.

From the results obtained here, we can see that several common drinks fall below the ‘safe’ recommended pH level of 5.5. In order to minimise damage the following dental recommendation should be followed.

Dental recommendation

After acid exposure the enamel is softened and is vulnerable. Calcium salts in saliva will remineralise and harden some of the softened enamel given time. Therefore, DO NOT BRUSH your teeth straight after drinking an acid drink as the softened enamel will be further damaged by the brushing which will speed up the process of erosion - wait at least half an hour before brushing.

Teachers’ notes

The experiment requires that all the liquids under test are approximately the same temperature. They should therefore be prepared in advance. The experiment should take between 20 and 30 minutes to carry out.

Credits, comments and further info

This experiment was written by Pico Technology.