pH value: acids and bases

In short: The pH value shows how acidic or basic a solution is. The scale runs from 0 (strongly acidic) through 7 (neutral) to 14 (strongly basic).

In more detail: pH measures the concentration of hydrogen ions. Each step on the scale means a factor of ten.

In detail

• Examples: Stomach acid about 1 to 2, lemon juice 2, coffee 5, water 7, soap 9 to 10, bleach 12 to 13.
• Skin: Its acid mantle is at about pH 5.5. Very basic soaps attack it.
• Measuring: Indicator paper, red cabbage juice or an electronic pH meter.
• Neutralisation: Acid and base react to water and salt.
• Safety: Strong acids and bases burn. Wear goggles and gloves, never pour water into acid, but acid into water (aggregatzustaende).