What Is The Conductivity Of Distilled Water?


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Distilled water is a type of purified water that has gone through the process of distillation to remove impurities such as calcium, sodium, and magnesium. Because of this, distilled water contains no ions and therefore, has a low electrical conductivity range of 0.5 to 3 µS/cm.

Water is a valuable resource, and many people are aware that water can conduct electricity. However, different water bodies have different electrical conductance values because of their ion concentration. 

For example, seawater contains salts (NaCl), so it has a very high conductance value, while distilled water has a low conductance value and therefore, is a bad conductor of electricity.

What Is Electrical Conductivity?

Electrical conductivity (EC) is the ability of water to conduct an electrical current in a solution over a certain distance, usually measured in Siemens (S) per distance (microSeimens per centimeter; µS/cm). Occasionally, you may also come across the U.S units millimhos per centimeter (mmho/cm), another basic unit of measure of electrical conductivity. 

The ability of water to conduct electricity is due to the ion concentration within the water from dissolved solids and inorganic materials like carbonate compounds, chlorides, and sulfides. 

Ions present in water can conduct electricity because they have positive and negative charges. The electrolytes then split into positively charged particles called cations, and negatively charged particles called anions. The concentrations of anions and cations remain the same, so even though the conductivity of water increases when more ions are dissolved in water, the water itself remains electrically neutral. 

Electrical Conductivity Of Distilled Water

Most public drinking water supplies are purified. Water purification is important to reduce and remove the number of suspended particles, parasites, algae, viruses, bacteria, and fungi to make water safe for human consumption and use. Purified water is treated to remove chemicals and contaminants, but distilled water takes it one step further. 

Distillation is a water purification process that uses heat to collect condensed water in the form of water vapor. During the distillation process, the water is heated until a boiling point has been met. The water is then left until it vaporizes. The vaporized water is then collected into a condenser to cool, where it is converted back into liquid form. 

As distilled water is treated to remove both contaminants and minerals.  It is the removal of impurities and ions in the process that makes the conductivity of distilled water very low; the electrical conductivity range of distilled water is 0.5 to 3 µS/cm, which corresponds to a resistivity of 18 megohm-cm (MΩ).

As distilled water has a low conductance value, it is unable to conduct electricity. Distilled water is also a poor conductor because it only contains stable water (H2O) molecules that are bound by covalent bonds with no other free electrons to pass an electrical charge, making it a good insulator. 

Is Distilled Water Safe To Drink?

Distilled water is safe to drink, yet the taste is often very bland because it has been stripped of all impurities including calcium, sodium, and magnesium that are found in tap water. 

As distilled water lacks natural minerals that are necessary for human function, purified water or sanitary tap water is better for you. 

Distilled Water Uses

While distilled water may not be the first choice for drinking water supplies, it can be used in many industries and applications. These include the following:

  • Cooking and cleaning in domestic homes
  • Beverage industries
  • The manufacturing process of car batteries and radiators
  • General sanitization processes in health care facilities
  • Manufacturing medicines
  • Calibrating laboratory equipment
  • Aquariums 

Making Distilled Water Conduct Electricity

As mentioned, distilled water is a pure form of water that cannot generate electricity due to the absence of dissolved ions. However, you can make distilled water conduct electricity.

If you were to add an impurity like sodium chloride (NaCl), more commonly known as salt, the distilled water will become a salt solution containing sodium and chloride ions, resulting in conducting electricity. 

The free ions present in salt are what allow a voltage to flow through the solution and produce an electrical current. The more salt that is added to pure water, the greater the conductivity will be. 

What Affects The Electrical Conductivity Of Water?

Electrical conductivity is affected by temperature, substances dissolved in water, and the concentration of ions in a solution. These are influenced by both natural and human impacts. 

Natural impacts on the electrical conductivity of water include precipitation (rain), geology, and evaporation. Human impacts include agricultural and impervious surface runoff, septic leachate, and the use of road salts. 

Testing Electrical Conductivity In Distilled Water

Measuring the electrical conductivity of water tells us how many dissolved substances, chemicals, and minerals are dissolved in the water. Once the conductance of water is measured, the correct treatment can be applied. 

To accurately measure the conductivity of distilled water, a conductivity meter is used. A conductivity meter comes with a conductivity probe that attaches to the conductivity meter to display the reading. 

Once the conductivity probe is inserted into the water, an electrical current flows between the two electrodes inside the probe, reading the electrical current and providing the conductance value. 

Common Conductivity Values

  • Distilled water: 0.5 to 3 µS/cm
  • Tap water: 50 to 800 µS/cm
  • Freshwater: 100 to 200 µS/cm
  • Industrial wastewater: 10,000 µS/cm
  • Seawater: 55,000 µS/cm

Summing Up, The Conductivity Of Distilled Water

Conductivity measures the ability of water to pass an electrical current. Measuring electrical conductivity is essential in detecting the presence of impurities in water supplies. 

Distilled water is a form of pure water stripped of dissolved impurities and free ions. Distilled water is therefore unable to conduct electricity because it has a low conductivity range of 0.5 to 3 µS/cm. As distilled water has a low conductivity, it is useful in electrical and sterilization processes. 

If you have any questions regarding the conductivity of water or what conductivity probe will best suit your testing needs, do not hesitate to contact our world-class team at Atlas Scientific.

Conductivity Probes

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