Testing the pH of a liquid is important for a range of reasons both in the home and environment. The most common way to test pH is by using litmus paper, which comes in strips that are used to test a liquid's pH level. The paper turns different colors to indicate how acidic or basic a liquid is. The pH also can be tested using a pH meter with a probe or a field test kit, neither of which uses litmus paper.
Things You'll Need
- Probe and pH meter
- Glass container
- Octet comparator
- Indicator solution
- Test tubes
- Distilled water
Field Test Kit
Fill the test tube that comes with the field test kit to the mark with the test liquid. Make sure the fill level is as close as possible to the line so that the results produced are accurate.
Drip a few drops of the indicator solution into the test tube with the sample and give it a slight shake to mix the two liquids. Add as many drops as the test field kit advises to produce the most accurate results. The solution in the test tube should change color based on what its pH is.
Check the color change of the test liquid against the color chart in the octet comparator. The comparator is a small, usually black box with slots in the top to fit a test tube and a visible color chart on the front. Match the color of the sample to the same shade on the chart to determine the pH.
Probe and pH Meter
Rinse the pH meter's probe with distilled water and carefully pat dry with a paper towel before each test. This makes sure that nothing is on the probe that can affect the final result of the test. Make sure the pH has been calibrated to the manufacturer's specifications before starting any tests.
Fill a glass container with enough of the test liquid so that the tip of the probe will be fully submerged. Be sure to perform the test quickly after adding the liquid to the container as pH levels can shift quickly.
Dip the probe into the test liquid, making sure not to move it around too much. Stirring can slightly alter pH level in some liquids and nullify the readings. Watch the pH meter's display; it likely will fluctuate for a few seconds as it gathers the reading. Once it has settled on a final number, this should be the pH of the liquid sample.
Tips & Warnings
- Narrow and wide range field test kits are available; if you have an idea of what the range of the liquid is but want a more precise reading, get a narrow range kit. If you don't know the approximate pH, get a wide range kit.
- For both methods, perform the test at least three times and take an average of all the results in case of any mistakes with one test.
- When using the pH meter and probe, follow the manufacturer's specific instructions to the letter to get the most accurate readings.
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