How Do You Use a pH Test Strip?

A pH test strip is a quick and accurate way to check if a water-based liquid is acidic or alkaline (basic). Just about every liquid you encounter on a daily basis is acidic or basic. Whether you are a teacher or a student taking chemistry, electroplating metal or making sushi or salsa, you need to be aware of pH. This blog will help you choose the right pH test strip for the job.

What Does pH Mean?

The simplest definition of pH is that it measures how many hydrogen ions (H⁺) are present. A lot of hydrogen ions present means the liquid is acidic whereas very few means it is basic. The pH scale is logarithmic so that a change of 1 pH unit is equal to having 10 times as many or 10 times fewer hydrogen ions, e.g. pH 5 has 10 times more than pH 6.

Why Does pH Matter?

The list below shows the pH of liquids you might find at home. The pH of a liquid can determine many things ranging from color to corrosiveness to taste. It is especially important in biology since your body is in many ways a chemical factory. The pH of your mouth, stomach, small intestine, and blood are tightly regulated because of the different chemical reactions they support.

Note that the items listed as pH 0, 1, 13, 14 are very corrosive. Children should not handle these unsupervised. Wearing protective gloves and goggles when handling is recommended.

Which pH Test Strips do I Need?

We offer 4 triple pad pH test strips. If you are testing a variety of liquids that can be acid or base such as those listed above, go with the wide range acid base pH 1-14 test strips. If you are interested in acid and base in urine & saliva, use pH acid-base 4.5-10 test strips. If you are investigating acids, use the 0-7 pH strips & for bases, the pH 7-14 .

How Do You Read a Triple Pad pH Strip?

Triple pad pH test strips have 3 comparison points to help eliminate ambiguity in reading the correct pH. This is particularly helpful with liquids that are not completely clear like milk or tomato juice. Note that the color chart shown above with the common household items does not correspond directly to the color chart below.

pH 1-14 test strips for acid or base aqueous (water-based) liquids. Compare the wetted test strip to the color chart. The first pad (Pad 1) is the one closest to the end.

How Accurate are pH test strips?

If the color chart for a given pH strip is shown in 0.5 increments then the strip is correct to within +/- 0.25 pH units. The pH 4.5-10 test strips in the image below shows this. When the color chart shows increments of 1 pH unit then the strip is correct to within +/- 0.5 pH units. The strips and their color charts are all calibrated using standards based on the sun’s light spectrum. Fluorescent lighting for example can alter the appearance of both strip and color charts.

These strips measure accurately on either side of neutral pH. They are very popular for recording day-to-day changes in the pH of urine and saliva

What Chemicals are in pH Test Strips?

Our pH test strips use a variety of chemical indicators. You can find out more about them in Wikipedia or other chemistry references.

If you are interested in their structure or chemical makeup, enter them into our 3D Molecular Model Builder. If you do this, one thing you will notice is that all of them have 2 or more ring structures.

To anyone interested in molecular symmetry, the skeleton of many indicators is Triphenylmethane which possesses the “propeller” shape known as a C3 point group.