Precision Laboratories & Precision Europe manufacture a wide variety of pH test strips, some narrow-range, wide-range, acidic, basic, and so on and so forth.

what is pH?, acids, bases, pH scaleBut what is the meaning behind these pH measurements?!

Okay, so you’re probably not that concerned about pH, but just for kicks, let’s take a refresher course on acids, bases, and the pH scale.

What is pH?

pH is defined as the negative log of the hydrogen ion concentration, or pH = -log [H+].

Huh?

In simple terms, good ol’ H2O, water, dissociates into hydrogen ions and hydroxide ions.

H2O = H+ + OH

It has been established that any point in which the concentration of hydrogen ions [H+] and hydroxide ions [OH] equal 1×10-14.

[H+] [OH] = 1×10-14

To help make sense of this, the concept of p on the –log [ ] is used.

pH + pOH = 14

Here’s what we’re getting at:

When the pH is low (acidic), the pOH is high, and vice versa, when the pH is high (alkaline), the pOH is low. When the [H+] = [OH], the pH=7 (pOH=7). This pH is considered neutral.

No matter where you are in the world, it is standard to use pH as a measurement of hydrogen ions and hydroxide ions. pOH is not usually used.

Acid vs Base

pH, pH scale, hydrogen ion, hydroxide ion, acids, bases

Okay, enough of the math lesson. What does this mean to a non-scientist? Put simply, an acidic solution contains more hydrogen ions. Acidic solutions have a pH value below 7, giving them a sour taste.

A basic, or alkaline, solution contains more hydroxide ions. Alkaline solutions have a pH above 7, giving them a bitter taste.

The pH Scale

So now that we know about acids and bases, let’s take a look at the pH scale. Below are some examples of where common solutions land on the pH scale. (This scale uses the color chart from our pH 1-14 test strips.)

pH scale, pH 1-14, acids, bases

As you probably know, citric juices, such as orange juice and lemon juice, have a sour taste, which is consistent with their pH level. As you might suspect, this is why it’s called citric acid.

If you’ve ever had heartburn or acid reflux (due to excess stomach acid), then you may have tried the age-old remedy of baking soda water, which has a more bitter taste. Again, this is consistent with the pH of baking soda.

Ready to put this knowledge to use?

If you know you are testing a more acidic solution, then you should use a narrow-range pH test strip somewhere between 0 and 7. The same goes for an alkaline solution: use a pH strip somewhere between 7 and 14. If your solution has a more neutral pH, choose a mid-range strip, for example pH 5-9.

How narrow you go depends on how much you know about the pH of the solution you are testing. If you aren’t sure where your solution will fall on the pH scale, a broad-range strip, like our pH 1-14, is a better solution.

That’s it for this science lesson. Easy-peasy! Next week, we’re looking at common errors in pH measurement that will affect your results, so stay tuned!