The pH of it all

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When we talk about wine, we talk about acidity, and when describing wines, one of the typical ways to describe acidity in wine is to use the pH scale. Dedicated students of wine can easily quote 2.9 to 3.9 as the typical range of pH in wine.

I personally love the zip and zest of highly acidic wines and adore Mosel Riesling (the drier the better), New Zealand Sauvignon Blanc, and even 100% Sicilian Grillo. I’ll take the tongue-curling antics of a wine with a pH of 2.9 any day.

But what exactly is pH? You probably already know that it is a scale runs from 0 to 14 and measures how acidic or basic a substance is. But what does that mean? To answer this question we need to dive into some science…we can start with chemistry and biology, and might just have to visit the physics department (and if we are going there, it better be worth it). So here we go!

About the p and the H: First things first—the term “pH” stands for “power of hydrogen.” The term was invented in 1909 by the Danish biochemist Søren Peter Lauritz Sørensen, so originally the “p” stood for potenz (the German word for power). The “H” (for us absolute beginners) is the element symbol for hydrogen, and the pH scale reflects the concentration and type of the hydrogen-based atoms in a solution. (Note: some references define the “p” in pH as “parts” or “potential.”)

What’s hydrogen got to do with it: Hydrogen is the common element to all acids. What determines whether a solution is acidic or basic is the form and degree of saturation of hydrogen ions.

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Define ions, please: To put it as simply as possible—ions are atoms or molecules that have lost or gained an electron over the course of their travels. In the case of hydrogen, this can occur when water splits apart.  If a hydrogen atom loses an electron, it becomes positively charged and is known as a hydrogen ion (H+). If a hydrogen atom gains an electron, it becomes negatively charged and is known as a hydroxide ion (OH).

Hydrogen ions: An acid is a molecule that can split apart in water and release hydrogen ions (thus, acidic solutions have measurable concentrations of hydrogen atoms). Bases are stronger in hydroxide ions. In neutral solutions, the two are roughly equal and they cancel each other out (neutralize each other).  The way that these hydrogen molecules react in water is the basis for the pH scale.

Deliver me from logarithms: The pH scale is logarithmic. Logarithms are multiples of ten; that means that for every full integer on the pH scale, the strength of the acid or base increases tenfold. Thus a pH of 2 is ten times more acidic than a pH of 3—and a pH of 2 is 100 times more acidic than a pH of 4. If this seems confusing, consider another logarithmic scale, the Richter Scale, where an earthquake measuring 7 is ten times stronger than a 6.

Liquid required: A substance has to be water-based in order to have a pH. Powders and oils (such as vegetable oil or olive oil) cannot be measured on the pH scale. There are, however, several other ways of measuring acidity.

The neutrality zone: A 7 on the pH scale is neither acidic nor basic, and considered neutral. Distilled water is generally neutral, but other types of water are not. An interesting (kind of gross) fact is that  human blood is very close to neutral (just slightly basic) and often has a pH of 7.35 to 7.45. Any deviation from this ideal blood pH can have devastating effects on one’s health.

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Just the basics: In the wine world we deal with levels of acidity, but it is interesting to understand the types of substances on the other end of the scale.  Here are a few common items and their basic pH levels:

  • 8: Baking soda, sea water
  • 9: Toothpaste
  • 10: Milk of Magnesia
  • 11: Ammonia
  • 12: Soapy water
  • 13: Oven cleaner
  • 14: Drain cleaner

The equation for pH: Never mind. If you are interested (and have a logarithmic calculator and know how to use it) click here.

References/for more information:

The Bubbly Professor (who has not formally studied chemistry or physics since college) is “Miss Jane” Nickles of Austin, Texas… missjane@prodigy.net

About bubblyprof
Wine Writer and Educator...a 20-year journey from Bristol Hotels to Le Cordon Bleu Schools and the Society of Wine Educators

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