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Three ways to test pH levels in water

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Posted January 4, 2019

Water, being a liquid and a solution (i.e., when it’s not 100% pure H20) has certain chemical properties because of its makeup. All solutions are acidic, basic, or neutral, and this is determined by the pH (power of Hydrogen) scale, with values ranging from 0 to 14. Essentially, this is a measure of how many hydrogen ions are present or hydroxide ions are present.

Acidic solutions are found on the lower end of the spectrum (such as citric acid, at 2.2 pH) and can have millions of times more hydrogen ions than basic solutions. Basic solutions are found on the higher end of the spectrum (such as bleaches and oven cleaners, at 13.5 pH) and can have millions of times more hydrogen ions than acidic solutions.

Laboratorian using the pH meter in order to prepare a buffer solution. Image credit: CDC / Susan McClure, Public Domain

Laboratorian using the pH meter in order to prepare a buffer solution. Image credit: CDC / Susan McClure, Public Domain

A pH measurement of 7 is considered neutral. Water, in its purest form, has a PH level of exactly 7, and this provides the foundation for measuring pH levels. It is relatively easy to test the pH level of water and here are three ways to do that.

USING A PH METER

According to thehomedweller, firstly, consult with the manufacturer’s instructions and specifications to calibrate the probe and meter. One way to do this would be to test the probe by dipping it in a substance with a pH level that you are already aware of. It may be an idea to carry out the calibration exercise several hours prior to using it, if you are using the probe in the field rather than a lab. Clean the probe before using it by rinsing it with clean water and wiping the water off with a clean tissue.

Fill up a clean container with the water you wish to test. You will need to make sure that the water level adequately covers the tip of the electrode to get an accurate reading. You should let the container of water or  sit for a short time to allow the temperature to stabilize. The pH meter probe’s accuracy is affected by water temperature, so use a thermometer to measure the temperature of the water and adjust the meter to match.

Place the probe into the container of water and allow enough time for the meter to reach equilibrium. Read the pH meter to get the pH measurement of the water sample. The closer to 7, the purer the water you have.

USING PH PAPERS

Firstly, fill up a clean container with test water. You will need to make sure that the water level is deep enough to cover the pH testing strip.

Secondly, dip one of the test strips into the container of water for a few seconds. The testing strip will change color momentarily. Once the strip has changed color, you will then be able to find out the pH level.

Universal indicator paper for the measurement of acidity or alkalinity (pH indicator). Concentration of Hydrogen ions compared to distilled water. Image credit: Albarubescens via Wikimedia, CC BY-SA 4.0

Universal indicator paper for the measurement of acidity or alkalinity (pH indicator). Concentration of Hydrogen ions compared to distilled water. Image credit: Albarubescens via Wikimedia, CC BY-SA 4.0

The pH testing strip would have been supplied with a pH color chart. Using this pH color chart, match up the color of the dipped pH testing strip with the colors on the chart to find out the pH level of the sample water.

USING LITMUS PAPERS

Litmus paper works a little differently to pH papers and will only determine whether a solution is acidic or basic.

Firstly fill up a clean container with test water and make sure the water level is deep enough to cover the litmus paper strips.

Secondly, dip one of the test strips into the container of water for a few seconds.

Litmus paper will either be red and blue. Red litmus paper turns blue if it is dipped in a basic solution. Conversely, blue litmus paper will turn red if it is dipped in an acidic solution. This limited test will only be compatible with tests involving acidic or basic solutions. Neutral solutions with a pH level of 7 will not change the color of the red or blue litmus papers.

It’s helpful to remember that a pH reading of 6 (such as milk) is ten times more acidic than water, while seawater and eggs (pH 8) are ten times more basic than water. Acidic solutions tend to be acrid and burning; basic solutions can also be sharp and burning but are slippery.

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