If you’ve ever found yourself in a conversation nodding in agreement, even though you had only a vague of knowledge of the subject, you’re in good company. If the subject of that conversation was pH – or pH factor, for those who remember when it was commonly called that – you might want to keep reading. Next time it comes up, you won’t have to pretend to understand.
The first thing to know is there’s an argument over what pH actually stands for. You’ll find references to both “power of hydrogen” and “potential hydrogen,” depending on what you’re reading and which side of the argument the writer comes down on. There’s some interesting history to the argument. Mostly it has to do with which language – German, French, or Latin – and therefore which country, can take credit for the work of Danish chemist Søren Peder Lauritz Sørensen, who first introduced the concept of
the pH scale in 1909 at the Carlsberg Laboratory in Copenhagen.
The simple version is, pH is a logarithmic scale running from 0 to 14 that measures how acidic or basic (alkaline) a solution or substance is. On this 0-to-14 scale, 7.0 is neutral, the pH of pure water. Zero (the extreme acidic end of the scale) is the equivalent of battery acid, or hydrochloric acid. Fourteen, the extreme alkaline end of the scale, is the equivalent of liquid drain cleaner or caustic soda, also know as lye. In between the extremes are these:
- normal stomach acid – 2
- upset stomach acid – 1
- tomatoes, acid rain, and black coffee – 5
- bread, potatoes, milk, and normal rain – 7
- seawater and eggs – 8
- milk of magnesia – 11
- ammonia – 12
- bleach – 13
The “Acid Touch”
Closer to home, human skin and blood fall on different sides of neutral. Until 2006, the pH of human skin was generally considered to be about 5.5. But a 2006 International Journal of Cosmetic Science study demonstrated average skin pH to be closer to 4.7. Our skin is acidic, closer to bananas than salmon, more so than we thought for a long time. Our blood, though, is alkaline, falling in
the 7.35 to 7.45 range. Most often, when the pH of the body is cited, it’s this blood pH that’s meant.
Closer to our Botanie home, cold-process soap is naturally alkaline. It is normal for soap to have a pH between 8 and 10.5. Commercial, industrially made soap has an average pH of 10.5. The pH of handmade cold-process soap can be as low as 8.5.
The focus here has been on the more simply understood and commonly applied aspects of pH. For those wanting more depth, more exponents, more numbers in general, pH won’t let you down. Whether it’s the molar concentration of hydrogen ions or the negative logarithm of the hydrogen ion concentration, there is plenty of science and math to be had.