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Deionized water, which is also known as demineralized water (DI water or de-ionized water; can also be spelled deionised water), is water that has had its mineral ions removed; cations such as sodium, calcium, magnesium, potassium, manganese and iron and anions such as chloride, sulfate, nitrate, bicarbonate, and silica. Deionization is a physical process that uses ion exchange resins that exchange out the mineral salts from water. The majority of water impurities are dissolved salts. Deionization produces a high purity water that is generally similar to distilled water, and this process is quick and without scale buildup. Deionization does not significantly remove uncharged organic molecules, viruses or bacteria, except by incidental trapping in the resin. Deionization removes cations from water by exchanging them for hydrogen ions (H+) on the resin and removes anions from water by exchanging them for hydroxide ions (OH) on the resin.
Demineralization will typically remove all these salts except for traces of sodium and silica.
| Cations |
Anions |
| Calcium Ca++ |
Bicarbonate HCO3- |
| Magnesium Mg++ |
Chloride Cl- |
| Sodium Na+ |
Sulfate SO4-- |
| Potassium K+ |
Nitrate NO3- |
| Iron Fe++ |
Silica SiO2 |
Conductivity & Resistivity
Resistivity is the reciprocal of conductivity:
Specific Conductivity = 1/resistance
Specific Conductivity = 1,000,000/resistance = micromhos
| Resistance in Ohms |
Conductivity in micromhos |
Approximate TDS |
| 18,000,000- 18 megohm |
0.055 |
0.0 ppm |
| 10,000,000- 10 megohm |
0.10 |
<0.01 |
| 5,000,000- 5 megohm |
0.20 |
<0.1 |
| 1,000,000- 1 megohm |
1.0 |
<0.5 |
| 100,000- 0.1 megohm |
10.0 |
<2.0* |
* Effluent containing NaOH, due to trace NaOH from SBA-OH
Water Quality for Various Processes
Battery Water - Approximately 30 micromhos/cm
Process Applications - Typically .1 to 10 micromhos/cm
Reagent Grade (Lab) -0.05 to 5 micromhos/cm
Semi-conductor - Greater than 17 megohms/cm
Contact General Water for DI Water Service
Located in suburban Philadelphia, General Water is a regional service company offering portable DI water tanks, parts and service. Contact us for further assistance.
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Technical Resources
