pH Measurement of Pure Water

Pure water can take many forms. Pure water can be considered as either tap water, filtered water, or distilled water. In all cases, keeping track of the minerals in the water is essential to making sure the water being used is ideal for the application it is needed for.

 

A form of pure water is distilled water. Distilled water is important for applications such as pumping or automotive batteries. In the automotive industry, distilled water is desirable for lead acid batteries. Because distilled water is free of impurities and minerals, automotive companies will use distilled water to top off car and truck batteries. Tap water will severely reduce a battery lifespan due to the ions found in the water. Also, for internal engine components (car radiator, cooling systems, etc.), using tap water can cause rusting and build-up in the system, leading to higher costs and potential damage.

 

Also, distilled water may sometimes be used to top off aquatic applications but should not be used as the main source of water. Distilled water does not possess enough minerals to support an aquatic ecosystem; it should only be used when combined with tap or filtered water. When tap or filtered water evaporates from an aquarium, it leaves behind minerals. A constant topping off an aquarium with tap or filtered water will make the water concentrated with minerals; instead, use distilled water to mix in with a certain amount of tap or filtered water so that it will be more beneficial for the fish and other living creatures/plants in the aquatic system.

 

Distilled water contains absolutely no minerals. It is one of the most pure water available; however, it is dangerous for drinking. Trace minerals in drinking water can be beneficial for human health, but they can cause system build-up in applications where such trace minerals pose a problem.

 

Unfiltered tap water typically contains chemicals that can interact with water to alter the pH. Filtered water can range from water that is filtered through a simple type of system to an intricate filtration system. Before using filtered water for an application, it is important to make sure that the minerals and chemicals in the water will not damage the filtration system. Also, when using either filtered water or tap water for an application, check to make sure that the minerals and deposits in the water will not hinder or damage the application it is used in.

 

Producing pure water involves processes such as distillation, boiling, reverse osmosis, microfiltration, carbon filtration, and many other processes. Minimizing the contact pure water has to air will prevent the water from dissolving gases out of the air. For example, the water can absorb carbon dioxide in the air very quickly and within 60 seconds, the pH of pure water can decrease by one pH unit or even more.

 

Cross contamination must be avoided to keep the water pure and free of any mineral deposits. For distilled water, use containers such as glass to help prevent unwanted water contaminations.

 

Determining the pH of pure water can be difficult. The pH of pure water is seven. In the pH scale, seven is the neutral point—neither alkaline nor acidic. Since pure water has low ionic strength and conductivity, using an electrode to calibrate the pH might prove to be challenging.

 

Temperature compensation is important. When using a meter, checking the precision of the pH meter should be done regularly to make sure the water is pure.

 

The S8000 series modular pH platform is great for measuring pH requirements in low ionic conditions. Low ionic samples such as pure water applications can cause pH electrodes to appear drifty and unstable, making it difficult to use as a process control. For this reason Sensorex offers special models of our most popular electrodes such as our S8000CD-LC for use in low ionic conditions where the conductivity levels are less than 100 microSiemens.

 

To withstand the low ionic conditions of pure water, the chemistry inside the S8000CD-LC is balanced creating a pH and reference cell well suited for these types of applications. The result is an electrode which is stable and repeatable which will allow users to utilize them for process control.

 

Another unique feature of the S8000 series is its cartridge style desigh with module available for submersion and inline configurations as well as optional accessories for temperature compensation, ground loop interrupt, unity gain pre-amplifiers, differential amplifiers and two-wire loop powered blind transmitters.