The 10 Best pH Testers
What Exactly Is pH And How Is It Measured?
pH is a measurement of the relative amount of hydroxyl and free hydrogen molecules in a liquid. Liquids with higher levels of hydroxyl are considered basic or alkaline, while a liquid that has a higher level of free hydrogen ions is considered acidic. Pure water at 25 degrees Celsius has a pH of 7.0 and is considered neutral. This means it has an equal amount of hydroxyl and free hydrogen atoms. All other measurements are based against the 7.0 neutral standard. Acids and bases can be used to counteract each other in a liquid until a neutral balance is achieved.
The pH scale ranges from 0.0 to 14.0. The lower the measurement, the more acidic a solution, and the higher the measurement, the more alkaline. A measurement of 6.0, would be considered slightly acidic, while a measurement of 2.0 would be considered extremely acidic. The best way of comparing acid in a solution is by finding out "how many times as acidic" one liquid is versus the other. The easiest way to do this is by using a logarithm. The pH scale is based on a logarithm that gives us a standard for how many times as acidic a solution is against neutral. Each 1 point step up means a liquid is 10 times more alkaline, and each 1 point step down means a liquid is 10 times more acidic.
Temperature can also play a role in pH measurements. At warmer temperatures, a neutral pH will be lower than 7.0. This is because the forward reaction of the autodissociation of water is endothermically favored and the rate of ionization in water increases at warmer temperatures. The increased rate of ionization increases the concentration of hydrogen atoms, which decreases the pH level. This means that at 40 degrees Celsius, a neutral pH level would be 6.77 instead of 7.0.
The Importance Of pH
Whether we are looking at pH levels in relation to plant growth or upkeeping an aquarium, the optimal level can be the difference between success or failure.
In agricultural applications, pH levels will affect everything from root development and the availability of usable nutrients in a growing medium to the prevention of fungi growth and plant disease. While many plants can survive in a variety of conditions and some plants may thrive in more acidic or more basic soils, the majority of plants prefer a neutral to slightly acidic growing medium. The ideal range for most plants is between 6.0 and 6.5. When growing mediums are highly acidic, manganese and and aluminum levels can become toxic to a plant. At levels of 7.0 or higher, minerals like magnesium, phosphorus and calcium can become unavailable.
In aquariums, maintaining the proper pH range can help your fish thrive. If you have a saltwater aquarium, a slightly alkaline water in the 8.1 to 8.4 range can offer your fish a natural antiseptic effect and help them resist bacteria and illnesses. It can also slow down the rate at which coral calcifies. Observing changes in your water's pH can even give you an early warning sign that your marine environment is undergoing other dangerous changes.
Common Methods For Measuring pH
There are three main methods for measuring the pH of a solution: the hydrogen paper method, the colorimetric method, and the electrode method.
The hydrogen paper method relies on special type of test paper called litmus paper. Litmus paper is a simple filter paper that has been treated with a mixture of natural dyes derived from a variety of lichens. These dyes change color in response to exposure to acidic and basic solutions, typically red when exposed to acid and blue when exposed to a base. The hydrogen paper method is the oldest form of testing pH levels and litmus has been used as far back as 1300 AD. Unfortunately, while it can tell us if a solution is acidic or basic, it doesn't give us a precise numerical measurement.
The colorimetric method is similar to the hydrogen paper method as it uses the natural color changing reaction of chemicals when exposed to acids and bases to determine pH levels. In this case, indicator reagents like phenol red and bromthymol blue are used to produce the color. Instead of dipping a piece of paper into the solution and having the paper change color as with the hydrogen paper method, these indicator reagents are dropped into a small sampling of the liquid to be measured, and the sample changes color. It is slightly more precise than the hydrogen paper method as the liquid's color and intensity can be compared to a color graph to obtain a numerical pH level.
Currently the most common and most accurate way for measuring pH in home and laboratory settings is the electrode method. This method makes use of a probe and a meter, which must be calibrated before use in a pH buffer solution. The meter measures minuscule voltage differences between a reference electrode and the measuring electrode, and then converts these measurements into a numerical pH reading.