The pH scale typically ranges from 0 to 14. However, it's important to understand that this is a general guideline. It is possible to encounter pH values below 0 and above 14, though these are less common.
Understanding the pH Scale
The pH scale measures how acidic or alkaline (basic) a substance is. A pH of 7 is considered neutral. Values below 7 indicate acidity, while values above 7 indicate alkalinity.
- Acidic: pH < 7 (e.g., lemon juice, stomach acid)
- Neutral: pH = 7 (e.g., pure water)
- Alkaline (Basic): pH > 7 (e.g., baking soda solution, seawater)
Several sources confirm this basic range:
- The US EPA (https://www.epa.gov/goldkingmine/what-ph) states that the pH scale ranges from 0 to 14.
- The USGS (https://www.usgs.gov/media/images/ph-scale-0) also indicates a 0-14 range.
- LaMotte's Wide Range pH Test Kit (https://lamotte.com/wide-range-ph-test-kit-3353-01) and Wide Range pH Test Strips (https://lamotte.com/wide-range-ph-test-strips-3-2950) both cover the 0-14 range.
Practical Considerations and Limitations
While the 0-14 range is widely accepted, the accuracy of measurement depends on the testing method and the specific substance being tested. Some specialized tests, like those used for highly acidic or alkaline solutions in industrial settings, might go beyond this standard range. Additionally, standard pH test kits may have limited accuracy at the extreme ends of the scale, requiring “high-range” kits for accurate readings in highly alkaline conditions, as noted on Reddit (https://www.reddit.com/r/Aquariums/comments/yi77bw/whats_the_difference_between_ph_and_high_range_ph/).
Furthermore, the pH of different substances varies widely. For example, soil pH can range from highly acidic to moderately alkaline (https://www.qld.gov.au/environment/land/management/soil/soil-properties/ph-levels), and skin pH typically falls within the acidic range (https://pubmed.ncbi.nlm.nih.gov/18489300/).
