What is Deionized Water? Definition, Properties, and Uses

If you work in a laboratory, manufacturing plant, or any industry that requires ultra-pure water, you may have heard of deionized water. But what is deionized water? Simply put, it is water that has had all of its ions removed, resulting in a product that is nearly pure H2O.

Deionized water has several unique properties that make it ideal for various applications, from laboratory experiments to industrial processes. For example, deionized water has a very low conductivity, which makes it an excellent solvent for certain chemicals and materials. Additionally, deionized water is less likely to cause corrosion or damage equipment because it is impurities-free.

Key Takeaways

  • Deionized water is created by removing all ions from water, resulting in a nearly pure H2O product.
  • Deionized water has a low conductivity and is impure-free, making it ideal for laboratory experiments and industrial processes.
  • Deionized water is less likely to cause corrosion or damage to equipment than other types of water.

Definition of Deionized Water

Deionized water, also known as DI water, is a type of purified water that has had all of its ions removed through a process known as deionization. Deionized water uses specially designed equipment to remove ions from water. 

This process eliminates minerals, salts, and other impurities, leaving water free of contaminants that can negatively affect experiments, manufacturing processes, or other applications.

How does ion exchange work?

Ion exchange is a process that involves the exchange of ions between two solutions, typically involving a solid phase and a liquid phase. In the case of deionization, the solid phase is an ion exchange resin, which is generally made up of tiny beads that are coated with charged groups. When water is passed through the resin, the charged groups on the resin attract and bind to the ions in the water, removing them from the solution.

What does deionization remove from water?

Deionization is highly effective at removing a wide range of minerals and other impurities from water, including

  • Calcium
  • Magnesium
  • Sodium
  • Chloride
  • Sulfate
  • Nitrate
  • Silica

Deionized water is commonly used in various applications, and its high purity and lack of minerals make it ideal for use in applications where the presence of impurities could cause problems or affect the outcome of experiments or processes.

How many types of deionized water are there?

There are two main types of deionized water: Type I and Type II. These two systems are used in various industries, including pharmaceuticals, electronics, and power generation. They are also used in laboratories for multiple applications, such as analytical chemistry, microbiology, and histology.

Type I Deionized Water

Type I deionized water is the purest form, with a resistivity of at least 18.2 MΩ-cm and a total organic carbon (TOC) content of less than ten ppb. This type of water is suitable for critical laboratory applications, such as molecular biology, cell culture, and trace metal analysis.

Type II Deionized Water

Type II deionized water has a lower resistivity than Type I water, typically ranging from 1 to 10 MΩ-cm. It also has a higher TOC content, usually 10 to 50 ppb. This type of water is suitable for less critical laboratory applications, such as general chemistry, buffer preparation, and glassware washing.

Properties of Deionized Water

Properties of Deionized Water

As we have read by now, deionization is an effective way to produce high-quality water free of ions and minerals. In this section of the article, we will look at the properties of Deionized water in detail. Let us begin reading.

Physical Properties

Deionized or demineralized water is purified with mineral ions removed through ion exchange. Here are some physical properties of deionized water:

  • Colorless and odorless: Deionized water is transparent and has no distinct smell, taste, or color.
  • Low electrical conductivity: Deionized water has a low electrical conductivity due to the absence of mineral ions, making it a poor conductor of electricity.
  • Low surface tension: Deionized water has a lower surface tension than tap water, which makes it more effective at cleaning and rinsing.
  • High resistivity: Deionized water has a high resistivity, which means it resists the flow of electric current.

Chemical Properties

Deionized water has a neutral pH and is free from dissolved minerals and other contaminants. Here are some chemical properties of deionized water:

  • Low pH: Deionized water has a neutral pH of around 7, which means it is neither acidic nor alkaline.
  • Low dissolved solids: Deionized water has a deficient concentration of dissolved solids, typically less than ten parts per million (ppm).
  • Lack of minerals: Deionized water contains no minerals, such as calcium, magnesium, or iron, which can cause scaling and corrosion in industrial equipment.
  • High purity: Deionized water is highly pure and free from impurities, making it ideal for laboratory and industrial applications that require high cleanliness.

Process of Deionization

The Deionized water passes water through ion exchange resins that attract and capture ions, effectively removing them from the water.

How is deionized water measured?

Deionized water is typically measured in terms of its resistivity or conductivity. Resistivity is the measure of a material’s ability to resist the flow of electric current, while conductivity is the opposite, measuring a material’s ability to conduct electric current.

Deionized water has a very high resistivity due to the ions’ absence, making it an excellent insulator. This property makes it useful in various applications, including electronics manufacturing, where it cleans and rinses sensitive components.

Uses of Deionized Water

Uses of Deionized Water

Deionized water is used in various industrial, laboratory, and medical applications due to its high purity and lack of impurities. Its unique properties make it essential in many manufacturing processes and scientific experiments.

Industrial Applications

Deionized water is widely used in various industries due to its high purity and lack of impurities. It is used in manufacturing semiconductors, pharmaceuticals, cosmetics, and food and beverage. Deionized water is also used in cooling systems, boilers, and other industrial equipment to prevent the buildup of mineral deposits that can cause corrosion and reduce efficiency.

Laboratory Applications

Deionized water is commonly used in laboratories for experiments and cleaning. It is used in preparing solutions and reagents, as well as for cleaning lab equipment and glassware. Deionized water is preferred over tap water because it contains no minerals or other impurities that could interfere with the accuracy of experiments.

Medical Applications

Deionized water is used in various medical applications, including dialysis, drug manufacturing, and laboratory testing. It also produces medical devices, such as contact lenses and surgical instruments. Deionized water is preferred in medical applications because it does not contain any impurities that could cause harm to patients or interfere with the effectiveness of medical treatments.

Advantages and Disadvantages of Deionized Water

Advantages and Disadvantages of Deionized Water

Deionized water has many advantages and disadvantages that should be considered when deciding whether to use it in a particular application.


Deionized water has several advantages over other types of water. Some of the benefits of deionized water include:

  • Purity: Deionized water is very pure and does not contain any minerals, salts, or other impurities that can affect the quality of the water.
  • Consistency: Deionized water is very consistent in composition, making it ideal for use in various applications where character is important.
  • Corrosion resistance: Deionized water is less corrosive than other water types, making it ideal for applications where corrosion can be problematic.
  • Improved performance: Deionized water can improve the performance of specific equipment, such as boilers and cooling towers, by reducing the buildup of mineral deposits.


While deionized water has many advantages, it also has some disadvantages. Some disadvantages of deionized water include:

  • Cost: Deionized water can be more expensive than other types of water, making it less practical for some applications.
  • Lack of minerals: Deionized water does not contain minerals, which can be a disadvantage in some applications where minerals are required.
  • Corrosion risk: While deionized water is less corrosive than other types of water, it can still be corrosive to specific materials, such as copper and brass.
  • Special handling: Deionized water requires special handling and storage to maintain its purity, which can be a disadvantage in some applications.

Comparison with Other Types of Water

When comparing deionized water to other types, there are several factors to consider. Here is a table that shows some of the critical differences:

Type of WaterSourcePurityConductivityUses
Tap WaterMunicipal water supplyVariesHighDrinking, bathing, cleaning
Distilled WaterBoiled and condensed water vaporHighLowLaboratory experiments, medical procedures
Reverse Osmosis WaterFiltered through a semipermeable membraneHighLowAquariums, car washes
Deionized WaterTreated to remove ions and impuritiesHighLowLaboratory experiments, manufacturing processes

Tap water can vary in purity depending on the source and treatment process. It is generally safe for drinking and other household uses but may not be suitable for more sensitive applications.

Distilled water is also highly pure but can be expensive and time-consuming. It is often used in laboratory experiments and medical procedures where even small amounts of impurities can be harmful.

Reverse osmosis water is similar to deionized water in terms of purity but may still contain some contaminants due to limitations in the filtration process. It is often used in aquariums and car washes where high purity is essential but not critical.

Deionized water is the purest and most reliable form of water for many applications, but each type has unique properties and uses.

Safety and Handling of Deionized Water

When handling deionized water, it is important to take certain precautions to ensure safety and prevent contamination. Here are some guidelines:


  • Store deionized water in a clean, dry, and cool place to prevent contamination.
  • Keep it away from direct sunlight and heat sources.
  • Make sure the container is tightly sealed to prevent evaporation and contamination.


  • Wear protective gloves and goggles when handling deionized water to avoid contact with skin and eyes.
  • Do not drink or ingest deionized water, which may cause dehydration and electrolyte imbalance.
  • Do not use deionized water for medical procedures or injections, as it may cause harm to the body.
  • Avoid spilling deionized water on the floor or equipment, as it may cause damage or corrosion.


  • Dispose of deionized water following local regulations and guidelines.
  • Do not dispose of deionized water in the sewer or drainage system, as it may cause pollution and environmental damage.
  • Do not mix deionized water with other chemicals or substances, as it may cause a hazardous reaction.

By following these guidelines, you can ensure the safe handling and disposal of deionized water.


Where can I buy deionized water?

Deionized water can be purchased at most hardware stores, automotive stores, and online retailers. It is also commonly found in laboratories and industrial facilities.

What is the formula for deionized water?

Deionized water has the same chemical formula as regular water, which is H2O. The difference is that deionized water has removed all its ions through ion exchange.

What is the difference between deionized water and distilled water?

Deionized water and distilled water are both types of purified water, but they are produced using different methods. Distilled water is produced by boiling water and then collecting the steam, which is condensed into liquid form. Deionized water is produced through ion exchange, which removes ions from water.

Can deionized water be used for drinking purposes?

While deionized water is safe to drink, it is not recommended for regular consumption as it does not contain essential minerals found in regular drinking water. Deionized water is primarily used in industrial and laboratory applications where purity is essential.


Deionized water has several properties that make it ideal for use in these industries. It is free of minerals and other impurities that can cause damage to equipment or negatively affect research results. It is also highly pure and consistent in composition, essential for maintaining accuracy in scientific experiments.

Deionized water is used in many applications, including as a solvent, coolant, and cleaning agent. It also produces cosmetics, food and beverages, and other consumer products.