pH value

pH Value | Meaning

What is pH value?

The pH value, also known as acidity, is one of the properties of a liquid or aqueous solution. The term pH is derived from the Latin name "Potentia Hydrogenii". This says something about the concentration of hydrogen ions. These ions have the ability (the p in pH indicates potency) to strongly alter chemical constituents with which they come into contact. One can think of them as a highly corrosive substance. More information on how these processes are applied in practice can be found in our article on caustic soda dosing, a widely used alkaline liquid.

The pH value ranges from 0 to 14 where a pH value of 7 is considered neutral. The pH value is a logarithmic scale and says something about the ratio of H3O+ to OH- ions. A high concentration of H3O+ means that a liquid has a low pH value. Respectively, a high concentration of OH ions means the pH value is high and the liquid is alkaline. When the ratio between the two ions is equal and the acid-base ratio is optimal, the pH value is 7. This is pure water (distilled water), for example.

Liquids with a pH higher than 7 are considered alkaline. This can include liquids such as caustic soda. Liquids with a pH lower than 7 are considered acidic. Fluids with a high acidity are, for example, the better-known acids like hydrochloric acid and sulphuric acid.

pH Value | Measurement

The pH value can be measured in different ways:

  • Litmus test. Litmus is a natural blue-violet dye originally used for colouring textiles or food. Nowadays, this dye is mainly used for measuring pH values. This is because litmus takes on a different colour depending on the pH value. If litmus comes into contact with an acidic liquid (pH 7), it turns blue. 
  • pH sensor. These sensors use an electrochemical reaction. These sensors consist of 2 different electrodes. An electrode (glass electrode) that measures the number of H3O ions in the liquid to be measured and compares it with a reference electrode (silver/silver chloride electrode). The difference between the two electrodes provides that for the measurement of the pH value. For more information on the operation and applications of pH sensors, see our article on ORP value and redox
  • Titration. This is the most accurate way to determine the pH value of a liquid and is mainly used by science. It uses the ratio of H3O+ to OH- ions. In a liquid with a low pH value and a high concentration of H3O+, such as lemon juice, a strongly alkaline liquid like caustic soda is added. Just until the number of H3O+ ions equals the number of OH ions. This is the equivalence point.

Acidity per liquid

To further indicate the difference in acidity, we have a chart below showing some alkaline and acidic liquids and their corresponding pH value.

Low pH (acid) liquids

LiquidpH Value
Hydrochloric acid0
Sulphuric acid1
Lemon juice2
Acid rain4
Juice of a tomato4,5

Liquids with a neutral pH value (pH = 7)

LiquidpH Value
Distilled water7

Liquids with a high pH value (alkaline)

LiquidpH Value
Dishwasher detergent10,5
Household ammonia11,5
Oven cleaner12
Sink unblocker13
Soda lye13
The pH value is an important value for, among other things, the regulation of free chlorine in swimming water. For optimal chlorine action in bathing water, the pH value should be between 7 and 7.6

pH Value | Increase / Decrease

Especially for pools and spas, it is important to continuously measure and regulate the pH value of the water. For public pools, this is even mandatory. Especially with a low pH value of swimming water, this can lead to corrosion of the metal parts in the pool, but too low a pH value can also cause the bound chlorine in the swimming water to stink and cause irritations. Also, the chlorine will not work as well (disinfection is less). A combination of pH and measuring and controlling free chlorine or Redox

Increase pH level 

If you want to increase the pH value of water, for example, you need to add an alkaline liquid (high pH value). Caustic soda is often used for this purpose. In the diagram above, you can see, for example, that chlorine has a higher pH value. 

Lowering pH value

If you want to lower the pH value of water, for example, you should add an acidic liquid (low pH). Think for example of citric acid, sulphuric acid or hydrochloric acid. For more information on liquids and pH value, take a look at the chart above.

pH Value | Applications

pH and its measurement/control is used in various industries:

  • For keeping pool water and water in spas, for example, clean and pure;
  • Drinking water treatment;
  • Cast water used in horticulture;
  • Legionella control;
  • Wastewater treatment;
  • Food industry;
  • Pharmacy;
  • Energy (cooling water treatment).
Correct pH is important for drinking water treatment

pH Value | dosing pumps and systems

Within Emec's product range, we offer various solutions for pH regulation. We also offer a number of turnkey packages with dosing pumps incl. sensors and controllers. For more information about our solutions and how they can be applied in different industries, visit our page on complete solutions.

Dosing pumps suitable for alkaline and acidic liquids 

Chemical liquids with very high or very low pH values can be very corrosive for the parts of the dosing pump that come into contact with this liquid. We call these the "wet parts". Especially for these heavy acids and bases, we offer dosing pumps that are suitable for this. We offer pumps for highly alkaline liquids such as caustic soda, but also for highly acidic liquids such as sulphuric acid and acetic acid. Not sure which pump you need? We will be happy to help!

pH Sensors and Controllers

For the pH value, we offer a sensor that works on the electrochemical principle. Connected to a controller (Emec Centurio or LDS) or directly to a dosing pump with pH controller, the system can then automatically regulate the pH value in a liquid.

Prefer a complete dosing system for pH regulation?

At Emec Webshop, we also offer a number of panels and installations with dosing pump and matching sensors and controllers. In addition, we also offer pumps from the Emec WDPHXX series. The dosing pumps from this series are suitable for measuring pH and Redox or Free chlorine (in combination with flowblock). This makes these dosing pumps very suitable for swimming pools, for example.

Frequently asked questions about pH value (FAQ)

How do you increase pH?

To raise the pH, you can add alkaline substances to the solution. Examples of such substances are sodium hydroxide (lye), calcium carbonate (lime) or potassium hydroxide. These react with the acidic components in the solution and raise the pH.

How do you get the pH up?

You can raise the pH by adding bases. Bases react with the acidic components in the solution and neutralise them, increasing the pH. Make sure you add the right amount to achieve the desired pH, and check regularly with a pH meter.

How do you lower pH?

To lower the pH, you can add acidic substances to the solution. Examples are hydrochloric acid, sulphuric acid or phosphoric acid. These acids react with the alkaline components in the solution and lower the pH.

What does pH mean?

pH is a measure of the acidity or alkalinity of a solution. It is an important parameter in many chemical and biological processes. pH is measured on a scale from 0 to 14, with 7 being neutral. A low pH indicates acidity, while a high pH indicates alkalinity.

About Emec Metering Pumps

Emec is an Italian company that has specialised in dosing systems and measuring equipment for chemicals for over 35 years. This extensive experience and passion for the product is reflected not only in the reliability and innovation of the dosing systems, but also in customer focus. For example, Emec offers a 5-year warranty* (!) as well as excellent after-sale support.

* Warranty applies to the equipment and diaphragm only. Not for the wet parts such as the pump head.

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