1. The pH scale runs from 0 to 14; distilled water has a pH of about 7 and is considered neutral, and acidity increases by 10 times with each decrease in a whole pH number.

2. The pH scale is from 0 to 14, with numbers below 7 acidic (low on oxygen) and numbers above 7 alkaline.

3. On the Ph scale, it is very acidic and can dissolve a nail in about 4 days.

4. In this media the proton activity can be measured by using a glass electrode with an aqueous pH scale.

5. Despite this diversity and the fact that certain organisms can grow at extremes of the pH scale, generalities can be made.

6. If the approximate pH to be measured is known, the electrodes should be standardized, using two values of buffer solutions to calibrate the system at each end of the desired pH scale.