As soon as water comes in contact with air, CO2 gas starts to dissolve it, forming carbonic acid (H2CO3). What is distilled water? This results in the pH being lower than seven. D.I. *That test will produce a score from 1 to 14. Water. The Relationship between pH and Deionized Water . The topic of pH and water has been well documented over the years; however, there is still much confusion about its significance in high purity water applications. Deionized water is free of ions, which are charged molecules or atoms that occur naturally in water. Deionized water, like distilled water, is a very pure form of water. You must also keep in mind that water (Deionised Water, or Distilled Water) do not have a pH of 7. The pH of distilled water is theoretically about 7. This means that it typically needs to be used in tandem with another type of treatment, such as Reverse Osmosis, to ensure that all contaminants are properly eliminated from it. To determine the pH of **D.I 3. The basics of pH . In practice, it’s difficult to put an exact number on the pH of distilled water because simple exposure to air can dissolve carbon dioxide.. Why does the pH of a substance matter? To measure the pH of water accurately you will require pH Ionic Strength Adjusters. It is the assumption that because distilled water has been purified, it has a neutral pH of 7. * water, it is necessary to conduct a test using the pH scale, which measures whether or not a substance is an acid, a base or neutral 1. Where they differ is that deionized water is water that has had all the ions removed from it. The pH scale encompasses 14 orders of m agnitude of the concentration of the Hydrogen (H+) ion on a scale of 0 to 14. But this is not always the case because distilled water is very rarely 100% pure, and even more rarely has a pH …