Question
Asked 9th Sep, 2013

What is the difference between distilled water and deionized water (DI water)?

What may be the difference in the pH of distilled water and deionized water? Does deionized water have a greater pH value than distilled water?

Most recent answer

21st Nov, 2013
Ernő Keszei
Eötvös Loránd University
Concerning water droplets, a good quality distillation column can minimise their quantity and improve steam quality to almost 100 percent. If you need high purity water, the usual procedure is to deionise distilled water as DI - as explained before - does not remove non-ionic (e.g. organic) species.
There is a difference between high purity DI water and simple DI water. The latter is more "soft" only than tap water; it might even have a greater conductivity than distilled (or double distilled) water.

Popular Answers (1)

9th Sep, 2013
Kenneth W. Pratt
National Institute of Standards and Technology
Deionizing systems use a mixture of cation and anion exchange resins (usually in a mixed bed). These resins exchange cations and anions in the source water for H+ and OH-, respectively. The H+ and OH- combine to form H2O, leaving only the residual H+ and OH- produced by autodissociation (autoprotolysis), H2O = H+ + OH-; the equilibrium constant of this reaction = 1 x 10^-14 at 25 °C. So the pH of deionized (DI) water is close to 7 **at delivery** and the electrolytic conductivity is about 0.055 µS/cm (corresponds to resistivity ~18 MΩ cm, hence the - technically incorrect, as the units are incorrect - term "18 megohm" water). However, this is true only if the DI water **has not** been in contact with atmospheric CO2. If it is in equilibrium with atmospheric CO2, the conductivity is on the order of 1 µS/cm (resistivity ~1 MΩ cm) and the pH is ~5,6 , both owing to dissociation of the dissolved CO2 to H+ and HCO3-. DI (or any other CO2-free-) water avidly takes up atmospheric CO2 and rapidly approaches the equilibrated values of pH and conductivity. For this reason, conductivity sensors in DI systems are located immediately following the last resin bed (column) and the water is continuously circulated, so that the conductivity value is obtained before the water has a chance to take up any CO2.
Distillation relies on phase separation to eliminate the dissolved ions (which remain in the pot). However, the steam is in contact with the atmosphere, and distilled water generally has electrolytic conductivity and pH values simliar to those of DI water that has equilibrated with the atmosphere (i.e., pH 5.6 and conductivity 1 µS/cm). Distillation systems can only remove CO2 if elaborate measures are taken to avoid contact with the atmosphere (e.g., flushing with pure N2 and blanketing the product H2O with N2).
DI systems do not remove molecular species (e.g. sugar, most other organics) from the product water. However, many commercial systems include an activated charcoal (or similar) column that removes many organics. Distillation will remove nonvolatile molecular species, but not volatile ones (they distill over with the steam).
Note that DI systems do not remove dissolved O2, as it is a molecular species.
The same dissociation reactions occur in both distilled and DI water. DI resins can "bleed" organics, although many of these will be taken up by the activated charcoal.
125 Recommendations

All Answers (167)

9th Sep, 2013
Fahad Alghamd
Saudi Food and Drug Authority
Distilled water: salt-free with an ionic ions
Deionized water: free of ions and salts so fixed salts, so fixed pH and stable
9th Sep, 2013
Martin Chaplin
London South Bank University
The pH will depend on residual solutes and storage conditions. Carbon dioxide is particularly important. There is probably but not necessarily more acidity in distilled water.
9th Sep, 2013
Moonis Ali Khan
King Saud University
Distilled water is a water that has been boiled and condensed during this process almost all impurities removed. while, deionized water is a water generally free from ions like Na, Cl, K, Mg that are generally present is tap water usually for deionization process ion-exchangers are used. But still deionized water may contain organic junk matter.
1 Recommendation
9th Sep, 2013
Jack Silver
Teledyne ISCO, Inc
Distilled water has been heated and condensed. Non-volatile materials will be removed (most ionic materials, although thare's a small possibility of volatile materials, such as ammonium acetate for example, making it across if that somehow is in the starting water.
Deionized water has been passed over ion exchange columns replacing cations with hydronium ions, anions with hydroxyl ions which combine with the hydronium ions. This is often passed over carbon filters to remove organic compounds.
I've also heard the term "deionized water" used with conjunction with reverse osmosis systems. I do not know if the term "deionized water" is strictly correct with these RO systems, but some of these systems deliver 18 meg Ohm water as well.
1 Recommendation
9th Sep, 2013
Shailendra Dwivedi
All India Institute of Medical Sciences Gorakhpur
yes as above mentioned but at current distilled water is generally after steam condensation stored in brass metal so again there is chance of ionic impurity and lighter ions could also moved with steam and in deionized water the ionic impurities are removed due to ion exchange with H and OH- exchanger but the impurities of organic compound still persist.
2 Recommendations
9th Sep, 2013
Kenneth W. Pratt
National Institute of Standards and Technology
Deionizing systems use a mixture of cation and anion exchange resins (usually in a mixed bed). These resins exchange cations and anions in the source water for H+ and OH-, respectively. The H+ and OH- combine to form H2O, leaving only the residual H+ and OH- produced by autodissociation (autoprotolysis), H2O = H+ + OH-; the equilibrium constant of this reaction = 1 x 10^-14 at 25 °C. So the pH of deionized (DI) water is close to 7 **at delivery** and the electrolytic conductivity is about 0.055 µS/cm (corresponds to resistivity ~18 MΩ cm, hence the - technically incorrect, as the units are incorrect - term "18 megohm" water). However, this is true only if the DI water **has not** been in contact with atmospheric CO2. If it is in equilibrium with atmospheric CO2, the conductivity is on the order of 1 µS/cm (resistivity ~1 MΩ cm) and the pH is ~5,6 , both owing to dissociation of the dissolved CO2 to H+ and HCO3-. DI (or any other CO2-free-) water avidly takes up atmospheric CO2 and rapidly approaches the equilibrated values of pH and conductivity. For this reason, conductivity sensors in DI systems are located immediately following the last resin bed (column) and the water is continuously circulated, so that the conductivity value is obtained before the water has a chance to take up any CO2.
Distillation relies on phase separation to eliminate the dissolved ions (which remain in the pot). However, the steam is in contact with the atmosphere, and distilled water generally has electrolytic conductivity and pH values simliar to those of DI water that has equilibrated with the atmosphere (i.e., pH 5.6 and conductivity 1 µS/cm). Distillation systems can only remove CO2 if elaborate measures are taken to avoid contact with the atmosphere (e.g., flushing with pure N2 and blanketing the product H2O with N2).
DI systems do not remove molecular species (e.g. sugar, most other organics) from the product water. However, many commercial systems include an activated charcoal (or similar) column that removes many organics. Distillation will remove nonvolatile molecular species, but not volatile ones (they distill over with the steam).
Note that DI systems do not remove dissolved O2, as it is a molecular species.
The same dissociation reactions occur in both distilled and DI water. DI resins can "bleed" organics, although many of these will be taken up by the activated charcoal.
125 Recommendations
Deleted profile
The deionized water is obtained by ion exchange, through the resinie-exchange, and the pH usually is basic (hardly is acid), while the water is distilled a simple evaporation-condensation and normally when it is fresh has an almost neutral pH, if is left open for a while the pH may reach 4.5-5 (equlibrio with CO2 environment).
1 Recommendation
9th Sep, 2013
Kalyan Kumar Dhar
University of Liberal Arts Bangladesh (ULAB)
Deionized water, also known as demineralized water / DM water (DI water, DIW or de-ionized water), is water that has had its mineral ions removed, such as cations like sodium, calcium, iron, and copper, and anions such as chloride and sulfate.
9th Sep, 2013
Kalyan Kumar Dhar
University of Liberal Arts Bangladesh (ULAB)
Distilled water is water that has many of its impurities removed through distillation. Distillation involves boiling the water and then condensing the steam into a clean container.In chemical and biological laboratories, as well as industry, cheaper alternatives such as deionized water are preferred over distilled water. However, if these alternatives are not sufficiently pure, distilled water is used. Where exceptionally high purity water is required, double distilled water is used.
9th Sep, 2013
Subramaniam Sivakumar
Sri Sankara Arts and Science College
Distilled water is an sterilized water whereas deionized water is devoid of ions.
1 Recommendation
9th Sep, 2013
David Moyer
Texas A&M University
The absolute best answer to this question is: take a sample of both DI and distilled water and actually TEST the pH yourself before you decide which one you want to work with. The water you find in a chemistry lab will typically range in pH from 5.6 up to 9, depending on the specific application you're working with and the source of the water. DI typically will have slightly different pH from distilled water, but the actual difference depends on where you get the source water. Here in Texas, we have a LOT of sodium and calcium in our water so our tapwater pH is right around 9, whereas where I lived in NH the biggest thing was iron and manganese so the pH was a little lower... and the water in southern NJ has a lot of organic acids so its pH (of natural waters not tapwater) is slightly acidic. DI will remove most of the mono-atomic ions but not the big stuff like those organic acids unless you augment the deionizer with some sort of filtration system. Distilled water will remove nearly all of the organic acids and other big molecules easily, but the "salt" content never actually gets all the way to zero (though it comes close enough for most work). Someone else mentioned CO2 contact... well, practically speaking BOTH DI and distilled water will be in contact with the air at some point so yes there is some gas that gets dissolved into the water but I have never seen distilled water go so low as pH 5.5. I have seen it get down to 6 though. Like I said, the best practice is to test the water in your lab before you use it. That way you know what YOUR conditions are.
1 Recommendation
10th Sep, 2013
Mukram Ismailsab
Gulbarga University
Distill water is not sterilised one..
1 Recommendation
10th Sep, 2013
Khaled Habiba
University of Texas MD Anderson Cancer Center
Distilled water is usually filtered by evaporation-condensation procedures to separate chemicals and impurities added in water.DI water is usually prepared by passing water through filters and columns which attract ions inside water. The DI water is used in washing, cleaning, preparation of suspensions, and electrophoresis buffer. Distilled water is usually used to water cooling for some delicate devices such as solid state lasers and it's not recommended for biochemistry activities or biological solutions. I recommend you to use nanopure water or MilliQ water which is a mixture of both Distilled and DI water with some additional filtration using millipore filters if you care about high purity. The pH of the milliQ water is neutral 7 and you can adjust it then using some buffers if you are willing to use it in some bio applications.
2 Recommendations
10th Sep, 2013
Philip Quinn
quchem
We must be careful to fully explain the term "distilled water" as it is possible, especially in simple distillation to transfer droplets of water (from the boiling bulk phase) along with the gaseous water phase (note visible steam contains small water droplets --- this is termed "wet steam" as opposed to "dry steam" which is not visible and does not contain water droplets). Water quality also depends on the microbiological burden (load/content). For "high quality" distilled water the distillation should be carried out in "inert" equipment and involve fractional distillation to eliminate water droplet carry-over from the boiling bulk phase ----- the pharmaceutical industry uses multi-distillation systems for generating very high quality distilled water since elimination of water droplet carry-over prevents microbial carry-over of either viable bacteria or endotoxins (released from dead bacteria).
19 Recommendations
10th Sep, 2013
Olivier Schalm
Hogere Zeevaartschool Antwerpen
ionized water contains CO2 in the water, making it slightly acid. The pH is sufficient to corrode copper tubes.
11th Sep, 2013
vipul Davariya
Distilled water: The water molecules have the boiling point of 100°C or 212° F. Other substances have different boiling points. The substance that boils at a lower temperature evaporates first. The boiling point of various impurities is higher, and, theoretically, they will begin to evaporate, when the water has already boiled out. The substance that boils at a lower temperature evaporates first. Due to this difference the water is separated. As a result, theoretically after the distillation the absolutely pure water is obtained. Actually, organic substances, which have similar boiling point than that of water can slip in the distilled water. For example, if the water contains the oil drops they can be found also in the distillate. There are practically no salts in the distilled water, because the salt boils at a much higher temperature. To eliminate the problem of organic substances, the distillers have pre- and post water filters.
***The absolute advantage of the distilled water is the complete absence of harmful substances.
Deionized water is deeply demineralized, ultrapure water with the resistivity close to 18 megohm-cm. It is used in microelectronics, printed circuit boards, instrument manufacture, pharmacy, washing liquids, etc.
In order to obtain the high quality pure deionized water, a multi-stage water purification process can be used. After pre-cleaning, the water is supplied to the reverse osmosis membrane, and then the water is filtered through a special deionization medium, which removes the rest of the ions in the water. The purity of deionized water can exceed the purity of distilled water.
1 Recommendation
11th Sep, 2013
Nodirali S. Normakhamatov
Tashkent Pharmaceutical Institute
Distilled water can contain CO2 which can produce H2O+CO2->H2CO3->H2O+CO2, depending which system of distillation is used for. That is why pH value of simple distilled water is lower than 7.0. Usually, pH value of water is lower when distillation equpment is made by methalic parts. Therefore bidistilled water (twice-distilled water) produced by glass distillators. Deionised water just a water which passed through ionexchange resin. Sometimes its pH value is higher than 7.0.
11th Sep, 2013
Philip Quinn
quchem
Deionised water is actually impossible to achieve ---- even if you had water which was 100% pure it will still contain ions --- both H+ (PROTONS)/HYDROGEN IONS) and OH- (HYDROXIDE IONS) since pure water undergoes auto-dissociation. At room 25C the concentration of H+ and OH- ions are equal and are approximately 1 x 10*-6 molar ----a very small concentration but nonetheless this means 100% pure water still contains ions --- meaning fully deionised water is impossible to achieve.
11th Sep, 2013
Philip Quinn
quchem
Sorry for typo ---- 1 x 10*-7 molar
11th Sep, 2013
Gobinda Behera
CSIR-Institute of Minerals and Materials Technology
It is very difficult to measure the pH of pure water. Distilled water is produced by a process of distillation. Distillation involves boiling the water and then condensing the vapor into a clean container, leaving solid contaminants behind. Distilled water can absorb CO2 and can form carbonic acid as a results its pH falls i.e. <7( 5.8). Deionized water is also known as demineralized water from which its mineral ions have been removed, such as cations like sodium, calcium, iron, and copper, and anions such as chloride and sulfate. Deionization is a chemical process that uses specially manufactured ion-exchange resins which exchange hydrogen ion and hydroxide ion for dissolved minerals, which then recombine to form water. However, deionization does not significantly remove uncharged organic molecules, viruses or bacteria etc. The exact pH of the deionized water can't be detected. It may be greater or smaller than 7.
11th Sep, 2013
Alexander J. Babchin
Alberta Research Council (ARC)
Good answer by KEN !
1 Recommendation
11th Sep, 2013
Gobinda Behera
CSIR-Institute of Minerals and Materials Technology
Me agree with Prof. Babchin that Prof. Habiba has nicely explained the topic. Hope these could clear the doubt of Jenish.
11th Sep, 2013
Guohua Zhou
Lingnan Normal University
I do agree with Kenneth Pratt very much. His answer is so detailed and precise. As mentioned in the answer, the pH of DI water will be below 7, ~5.6, if it is equilibrium with atmospheric CO2, which must happen after it is produced.
1 Recommendation
11th Sep, 2013
Ghouse Modin Nabeesab Mamdapur
Synthite Industries Pvt. Ltd
Differences
1. Distilled water-It is free from microbiological contaminants like worms insects etc.
Deionized water-Which is free from minerals with low conductivity
2. Distilled water-Purification from macro contaminants
Deionized water-the one with free from above additional to free from all kinds of ions.
2 Recommendations
11th Sep, 2013
Rogers Harry-O'kuru
United States Department of Agriculture
Both Pratt and Davariya hit the mark quite sucinctly. Each contributor is aware of the difference between the terms to an extent. Both systems are efforts to demineralize the water for specific needs. While distillation tends to leave most dissolved mineral content of the water in the distilation pot, the process is usually unable to remove codistilling organics without further treatment of the distilate whereas DI systems are usually set up with this contingency in mind. Water itself is the "big gorilla" of a challenge because of its uniqueness. One really could not get pure water in spite of all the effort because of its autoprotolysis tendency and the propensity to absorbe CO2 and dissolve most things in its path except glass. So we do the best we can to minimize the amount of impurities using these systems. There is really no perfect system by itself.
1 Recommendation
Deleted profile
The deionized water, obtained by a process of ion exchange resins, has a pH very different from the distilled water.
Cosideriamo of fresh deionized water, the pH may be acid (use of cationic resins in acid form) or basic pH (use of anionic resins in basic form). The distilled water of fresh normally has a pH near neutral.
11th Sep, 2013
Laszlo Jicsinszky
Università degli Studi di Torino
Mario:
Usually the deionized water is (should be) neutral. The outcome of deionizing equipment (usually a flask, connected to the water source, is filled with strong anionic and cationic exchangers, valves and tubes, etc) is controlled by conductivity, i.e. if the conductivity is over a certain small value the magnetic valve stops the flow. The conductivity limits is usually less than 1-5 microS. This means the deionized water, if your equipment works properly, should be neutral. Additionally, the increasing conductivity necessarily decreases the pH. If your fresh deionized water is not neutral, the deionizing flask is exhausted and needs change.
Of course, after a couple of hours, if the container is not closed, water absorbs CO2.
The freshly distilled water is usually contains CO2, except when the collector of the condensed water is assembled with a basic (usually KOH) tube. Sometimes the once distillled water may contain metal ions, depending on the distillation equipment.
It is also true that conductivity measurement is more precise than pH measurement in poorly ionic environment.
12th Sep, 2013
prof V.S Muralidharan
Central Electrochemical Research Institute
Distilled water is the steam condensed to room temperature; theoretically it is a non conductor---De ionised water contains all salts in lesser amount and has appreciable electrical conductivity.
Deleted profile
according to U.S.P pH for double distilled water is 5-7 and for water for injection is 5.4-5.5. Theoretically pH is taken as 7 for both Water For Injection and Distilled water but due to formation of carbonic acid and and due to heating to 120 degrees temperature formation of precipitate of alkaline earth metals occurs which is another reason for the acidic pH of both of these.
12th Sep, 2013
Philip Quinn
quchem
Not only is the pH of water dependent on the level of dissolved carbon dioxide but also on the temperature of the water as this effects the degree of ionic dissociation ------- of course the calibration of the pH meter/instrument is also very important.
Deleted profile
The deionized water, obtained through the resins, even when the pH is neutral and low conductivity brings with it a series of neutral organic substances that can create serious problems in the experimental determinations. Distilled water does not present this problem and when it is recent and near neutral pH and low conductivity.Annulla modificheAlpha
12th Sep, 2013
Dr Sudhir Kumar Srivastava
Central Ground Water Board, India
If one wants to analyse dissolved silica in water samples then one should not use DI water as it may contain dissolved silica , however during distillation it remains in the pot / flask. Silica (SiO2) being neutral remains in the D I water even after passing through a mixture of cation and anion exchange resins used in a Deionizing system.
1 Recommendation
12th Sep, 2013
Belgacem Chandoul
Tap water contains calcium and microorganisms (usually dead). When deionised, limestone is removed, but microorgnismes allowed. When distilled, all impurities are removed. There is only water H2O.
For all chemical operations (dosage) the deionized water is suitable. But for medical applications (injections, etc.) distilled water is necessary.
13th Sep, 2013
Dr Sudhir Kumar Srivastava
Central Ground Water Board, India
Deionized water is produced by running water through a bed of a porous polymeric resin, which contains loosely bound hydrogen (H+) and hydroxide (OH-) ions. As water flows over the resin, dissolved charged chemical species in the water -- such as calcium and magnesium -- are bound to the resin, and hydrogen or hydroxide ions are released to take their place. These two ions will then combine to form water. The result is that many of the most common chemical contaminants are removed and replaced with water. The resin is regenerated occasionally to replace the lost hydrogen and hydroxide.
Distillation is a simple process in which water is heated to its boiling point and allowed to turn into water vapor, or steam. This vapor travels along a conduit to a different location where it cools and condenses back into liquid water. The result is that impurities are left behind in the original container and essentially only pure water is collected in the condensate.
Distilled water is generally more pure, since the distillation process, theoretically, only takes pure water over into the condensate collecting vessel. Any minerals or metals will be left behind, as well as biological contaminants, such as bacteria. However, it is possible for traces of some low-boiling chemical contaminants, such as volatile organic compounds, to be carried over into the condensate. As well, the process requires specialized equipment and fairly high energy input to boil the water. Deionization gives less pure water since it removes only dissolved minerals and some charged metal compounds. It will rarely remove organic or biological contamination. Deionization does have the advantages of being quick, inexpensive and low maintenance.
3 Recommendations
13th Sep, 2013
Parimal Vijay Naik
KU Leuven
Deionised water is purest form of water it is obtained through ion exchange resins to remove all ions. While distiled water is condensed water after heating it which still contains some salts and ions. Also if you check the conductivity of the both water you can find the difference in both.
deionised water is very important in semiconductor industries.
1 Recommendation
13th Sep, 2013
Alexander J. Babchin
Alberta Research Council (ARC)
We all can see that both kinds of water have their advocates. The problem can be resolved only if every one agrees on the measurement of undisputed Physical Parameter, the Water Conductivity.
1 Recommendation
13th Sep, 2013
Lijo Francis
New York University Abu Dhabi
Distilled Water: Water obtained after vaporization and condensation.
Deionized Water: Water obtained by passing through ion exchange resins.
1 Recommendation
13th Sep, 2013
Nodirali S. Normakhamatov
Tashkent Pharmaceutical Institute
I have doubt on opinion that the distiled water contains salts. What kind of salts do you mean and from where there are? So these salts can evapore before 100C? or they can make azeotrop mixture?
1 Recommendation
13th Sep, 2013
Jack Silver
Teledyne ISCO, Inc
@Nodirli- Distillation systems made of borosilicate glass may provide traces of sodium from the glass condenser. Someone earlier mentioned using a brass still, again, metal ions could leach out from the condenser. Remember also some salts are volatile (ammonium formate, ammonium acetate, for example- these are used in LC-MS for this reason) but I doubt these salts would be found in the feed water to a still.
13th Sep, 2013
Philip Quinn
quchem
Why not make your own pure water --- synthetically?
1 Recommendation
13th Sep, 2013
Nodirali S. Normakhamatov
Tashkent Pharmaceutical Institute
Jack, condenser material and impurities on it are another problem, I think. I am talking about a water distillation process. Furthermore, boiling points of that salts which you mean smaller than the water boiling point. Ammonium formate decomposes into formamide and water when heated. And boiling point of formamide is higher than 200C.
P.Quinn, I think there will be the same problem when water produced sythetically because of side products or even presence of slightly soluble products.
13th Sep, 2013
Philip Quinn
quchem
IF YOU USE PURE DRY HYDROGEN AND PURE DRY OXYGEN both of which are available in over 99.99% purity ---- in an inert "bomb" then carbon dioxide is absent ---- if the "bomb" is cleverly constructed with INBUILT pH PROBES then the pH of this synthetic water can be measured for comparison with distilled and deionised water --- very little side products present if raw materials are of high purity
13th Sep, 2013
Jack Silver
Teledyne ISCO, Inc
@Nodirali- please note the salts mentioned are commonly used for LC-MS, ELSD, and prep LC because they are sufficiently volatile to be easily removed, by lyophilization or rotary evaporation. These samples aren't heated very warm, for lyophilization, it isn't heated at all. ( http://www.lcgceurope.com/lcgceurope/data/articlestandard//lcgceurope/422004/128469/article.pdf for example of volatile salts and buffers for prep LC). If they can become volatile at modest temperatures, I'd expect them to by in the water to some extent.
Like I said, these probably aren't present in the water going into the still so the discussion is merely academic.
13th Sep, 2013
Nodirali S. Normakhamatov
Tashkent Pharmaceutical Institute
P. Quinn, I imagine how it is difficult to provide such condition which you mean to produce sinthetically water. I think it is more complicate than the redistillation and deionising process of water.
Jack, thank you, I understand, you are right, but anyway we should get a clearance of meaning "a distilled water" and but not just condenced water in any other condition (low temperature or pressure).
Yes, as you mentioned our discussion is just for academic purposes.
13th Sep, 2013
Philip Quinn
quchem
synthetic water is easy to make ----- http://www.nextenergynews.com/news1/next-energy-news11.2b.html --- have a read Nodirali before making such dismissive coments
13th Sep, 2013
Nodirali S. Normakhamatov
Tashkent Pharmaceutical Institute
dear P.Quinn, please do not teach me a school program with your dismissive comment. You show me an ideal condition or theory of water producing. Or otherwise give me an evidence that the produced water by this technology is absolutely free from any ions and salts. The discussion is about difference of distilled and DI water. Furthermore, which researcher for their daily experiments use such produced water? Be realistic!
14th Sep, 2013
Omar Abd Elkader
King Saud University
Distilled water is produced by a process of distillation and has an electrical conductivity of not more than 11 µS/cm and total dissolved solids of less than 10 mg/litre.
Deionized water, also known as demineralized water / DM water (DI water, DIW or de-ionized water), is water that has had its mineral ions removed, such as cations like sodium, calcium, iron, and copper, and anions such as chloride and sulfate.
16th Sep, 2013
Wayne Robarge
North Carolina State University
I think Kenneth Pratt from NIST gave the answer you were looking for. I would like to just add that one possible issue with mixed bed resins is the loss of small particles, and as noted, some dissolved organic molecules. We have a central system which I supervise and supplies deionized water for our building. In addition to the resin beds, we also have UV lamps in line to destroy some organics, and we have a 0.2 micron final filter before the water enters our distribution line. It is important when using resin beds, especially in a single lab environment, that you prevent channeling in the columns. Commercial systems usually have sufficient pressure to lift the bed and prevent channeling. This is much more difficult to achieve if you set up a your own packed resin columns in the laboratory.
Regarding distilled water systems, I agree with many of the comments thus far that a still cannot remove volatile organics. We had a number of faculty some years ago invest in double distilled systems to try and lower the N content of the water. They of course were using city water as the feed for their systems. Amines may be present in municipal water supplies due to various treatment processes. As such, the double distilled systems really did not solve their problem. I am not sure how the presence of the amines might impact the resultant pH of the product. I would be more concerned about trying to actually measure the pH of supposedly pure water given the standard pH electrodes used in most laboratories, even under a nitrogen or helium atmosphere.
4 Recommendations
16th Sep, 2013
Kenneth W. Pratt
National Institute of Standards and Technology
A few more comments on the previous thread of posts. Measuring the pH of either distilled or deionized water is not easy. It is much easier to measure tbe conductivity than the pH; inline pH measurements also contaminate the water (via seepage of KCl from the reference junction) and require periodic reconditioning. Conductivity monitoring has the further advantage that in addition to H+ and OH-, it detects other ions, notably Na+ and Cl-, that can be present and that do not (to a first order) influence the pH value. This is why manufacturers use it.
See ASTM D5464-11 for background information on pH and conductivity in high-purity water. The graph in Appendix X3 summarizes the effect of dissolved CO2 and NH3 at different levels on the pH and conductivity levels.
If a deionizing column is not constructed such that its exchange capacity is not equal for anions and cations or if its hydrodynamic efficiency to "scrub" incoming ionic species is unequal, then a situation could arise where one type of resin, e.g. the anion exchange resin, becomes exhausted, while the cation exchange resin still has remaining exchange capacity. In this case, the pH of the water and its conductivity could diverge substantially from the respective values for pure water (owing to the exchange of fewer cations than anions or vice versa). If this occurs, the pH would decrease (as in the example) or increase (if the cation exchange resin were exhausted). In either case the resistivity would *very* rapidly decrease from the nominal 18 MΩ·cm value. This situation should not occur in a well-constructed commercial column but could easily occur in a lab-constructed column. In any case, it is important to replace or recharge the resins well before this situation has a chance to occur. It is not easy to recharge a mixed-bed resin, as the anion and cation exchange resins must be quantitatively separated from each other before recharging them. Better to leave this task to the manufacturers.
As to distillation, anti-corrosion additives in commercial boiler systems can form azeotropes and these will not be separated on distillation. Commercial systems using fractional distillation and condensation at temperatures close to 100 °C can increase the rejection of volatile components with lower or greater volatility than that of water but cannot reject an azeotrope.
Producing water from pure H2 and O2 is not feasible for lab use, Apart from the large amount of heat produced and danger of explosion, if N2 is present, significant amounts of NOx will be formed and will contaminate the water (e.g., ion chromatography will detect NO3- present). There is also the possibility of H2O2 present in the product (which would not be detected by conductivity or pH measurements). If either gas is 99.99 % pure, the impurity gas will be present in the product water. If this impurity were CO2, a mol fraction of 0.01 % (= 100 µmol/mol, or 5.5 mmol/L) could be in the water. This is 1/4 the value that would be in air-equilibrated water, far greater than the output of a deionizing system.
5 Recommendations
17th Sep, 2013
Sandip Maurya
Los Alamos National Laboratory
Basically, there is no difference in quality of water..
However, the different way has been approached. Based on the application one can make choice.
1 Recommendation
17th Sep, 2013
Philip Quinn
quchem
Nodi do not attempt to lecture me -- I do not take a narrow perspective on such scientific matters --- measurement of pH ETC IS ALL RELATIVE AND WHAT IS IMPORTANT IS FOR THOSE ACTIVELY ENGAGED IN RESEARCH is to have an open mind --- measurement is not the issue but relative levels of chemical impurities is problematic for certain areas of scientific research. Rather than attempt to remove impurities from water I was merely suggesting that if researchers wanted extremely pure water then synthesis of water offered a possible and viable means of proceeding using water devoid of an unknown range of organic and inorganic impurities ---- do not take things personally Noddy
--- synthetic chemstry is easy for anyone with a sound background in chemical synthesis ---- just look around at all the wonderful chemicals produced synthetically.
2 Recommendations
20th Sep, 2013
István Fórizs
Research Centre for Astronomy and Earth Sciences
Dear Colleagues,
I have enjoyed very much all the comments in this topic.
Now I would like to know your opinion on how effective is method of boiling the distilled water for removing the dissolved inorganic carbon (DIC) from it.
20th Sep, 2013
Martin Chaplin
London South Bank University
Not efficient, Istvan. Carbon dioxide is soluble in boiling water.
1 Recommendation
20th Sep, 2013
Nodirali S. Normakhamatov
Tashkent Pharmaceutical Institute
Because of presence of carbon dioxide in the water boiling and decantation systems the DIC species (carbon dioxide, carbonic acid, bicarbonate anion, and carbonate) are always present in the distilled water. This problem may be solved by using an inert gas medium, I think.
20th Sep, 2013
Martin Chaplin
London South Bank University
Bubbling with helium has been found to work
1 Recommendation
20th Sep, 2013
Dr Sudhir Kumar Srivastava
Central Ground Water Board, India
Few addition of potassium permangnate in boiling water is often used?
1 Recommendation
21st Sep, 2013
prof V.S Muralidharan
Central Electrochemical Research Institute
potassium permanganate is used to remove organic impurities
Double distilled water is the best
Deleted profile
The deionized water is obtained by ion exchange with resins and can contain residues of metals in addition to the presence of organic sostane of different nature which can interfere with the experimental measurements even if the conductivity is low.
The water distilllata is obtained by evaporation and condensation. It turns out, if you take the proper precautions techniques (trappolo for CO2 and KMnO4), almost neutral is used especially fresh.
1 Recommendation
23rd Sep, 2013
Philippa Ojimelukwe
Michael Okpara University of Agriculture, Umudike
Distillation is essentially o physical process involving evaporation and condensation. The evaporated water molecules are allowed to condense back by cooling. This allows the separation from impurities and increasing the degree of water purity for specific purposes. De-ionization entails removal of ions that could come from other materials , hydrogen or oxygen and may involve DE-mineralization. The resin (cationic or anionic ) determines the efficiency and nature of the DE-ionization process and ultimately affects the final pH of water. However, some literature state that there is no difference between distilled water and DE-ionized water
1 Recommendation
Deleted profile
The deionized water is obtained by ion exchange with cationic and anionic resins, in theory we should obtain a neutral pH, in fact it may contain residues of metal ions (which determine a pH different from neutrality) in addition to the presence of organic substances of different nature which may interfere with the experimental measurements, even if the conductivity is low.
distilllata the water is obtained by evaporation and condensation and if you take proper precautions techniques (trap for CO2; use of KMnO4), the pH is almost neutral, especially if the distilled water is used immediately after the distillation.
1 Recommendation
23rd Sep, 2013
Kid Cowles
K.I.D.S. LLC
While you all have taught me so much about water in this discussion, I would like to simplify this a little bit.
First, I would like to ask Jenish what is the application that you are needing this information for?
Secondly, in my water quality testing, I have found that the Extech EC500, when calibrated, is a great tool for testing PH, TDS, Temperature, and more.
It is the first thing needed to find out the answer in your application. As we learned, water can change due to many variables, so you need to test yours. Then if more information is needed, continue. There are other water quality tests besides, what this instrument offers.
2 Recommendations
24th Sep, 2013
Jenish Patel
Ulster University
Hi Kid,
Thanks to all those who answered to this question. I learnt a lot from this :)
I am actually studying basic plasma-liquid interactions. I am studying the basic reactions when water is exposed to plasma. So, I was wondering over which one (distilled or deionized) would give more detailed analysis. Although I started with distilled water & measuring pH, temperature and conductivity, I am just wondering what difference it will make if I use deionized water.
24th Sep, 2013
Alexander J. Babchin
Alberta Research Council (ARC)
In my experience I had water of lower electric conductivity using Micropore Reverse Osmosis, than conductivity of Distilled Water. Thus, t had less ions dissolved over intrincically deionised H2O.
24th Sep, 2013
Kid Cowles
K.I.D.S. LLC
Jenish,
You should take a look at the Extech instrument I recommended.
It measures everything you are are looking for in your study so you can make the best determination for yourself. As we all learned, there are so many variables that can be introduced in water. While we can all speculate, the only answer will come from testing it yourself. When you do, please post your findings, so we can all see the results and learn from your experiment!
24th Sep, 2013
Philip Quinn
quchem
Reverse osmosis is excellent for deionising especially if the water is recirculated several times ----- the choice of membrane is very important and if the final water membrane pass(es) uses a charged 0.2micron membrane eg POSIDYNE then bacteria and bacterial debris is virtually eliminated.
24th Sep, 2013
Alexander J. Babchin
Alberta Research Council (ARC)
Distillation of water is no more than boiling the water into the steam and then condensing the steam back into the water, which is called distillate. Steam of 80 % quality is considered as a dry steam, still, 20 % of the mass of water is transported as tiny water droplets, with ions of initial water are still dissolved in them. So, many stages of distillation is required to get decent degree of de-ionization. Vodka is a good example. After primary distillation one gets moonshine with guaranteed headec after consumption. Professinally done VODKA has 5 distillation steps. In the case the number of steps is 3 or below, my recommendation is to have the cucumber brine ready for fixing grogginess.
Micropore Reverse Osmosis provides high quality pure water in 1 step.
2 Recommendations
25th Sep, 2013
Wolfgang H. Muss
Paracelsus Medical University Salzburg
@ALEX BABCHIN and all other cherished posters:
Good evening, dear Alex,
you might have brought the discussion (including your example with VODKA distillation) to the point. OK, lets try the whole thread again about triple distilled water + filter (pyrogen free) (:-))...
Best wishes and regards, Wolfgang
1 Recommendation
25th Sep, 2013
Alexander J. Babchin
Alberta Research Council (ARC)
Good evening, Wolfgan. Sure, as a Moscow born person I am qualified in quality of Vodka.
Then, I worked with steam assisted Heavy Oil Recovery in Canada, so, I am aware on the steam quality. I just put 2 and 2 together. LIVE EXPERIENCE.
2 Recommendations
30th Sep, 2013
Virendra Kumar Saxena
National Geophysical Research Institute
Yes Deionized water is more in pH than Distilled water.
Distilled water is low in TDS ( < 10 mg/lit ) and pH < 6.8 ); whereas Deionized water have TDS ( <25 mg/lit ) and pH <7.2.
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I am perfectly in agreement with Virendra Saxena
3rd Oct, 2013
Mukesh Kumar Raval
Gangadhar Meher University, Sambalpur
Double or triple distilled water is expected to be free from ions, soluble impurities, and microbial debris. DI water ensures removal of ions but not the other impurities. This is also reflected in Virendra's statement.
1 Recommendation
3rd Oct, 2013
Virendra Kumar Saxena
National Geophysical Research Institute
Thanks Mario and Mukesh
4th Oct, 2013
Fares Saleh
Aston University
Nice discussion,But would like to hear somthing about unit production cost of both
4th Oct, 2013
Philip Quinn
quchem
unit production costs will depend on:
1. The quality of the water used;
2. The daily volumes required or indeed the rate of usage (volume per unit time);
3. The quality of water required with respect to ionic content/conductivity; microbial quality; organic content.
4th Oct, 2013
Fares Saleh
Aston University
Thank you Quinn for ur quick reply
But assuming using same water(quality,flow rate ...etc.);which one is cheaper in cost?&how much?
RGDS
4th Oct, 2013
Alexander J. Babchin
Alberta Research Council (ARC)
DI water has lower cost. Tap water runs through Micropore unit under Tap pressue. No heating, no problems.
8th Oct, 2013
Ahmad Bashir
University of Peshawar
The difference is that of conductivity and pH.
10th Oct, 2013
Subodh Kumar Maiti
Indian Institute of Technology (Indian School of Mines) Dhanbad
Kenneth Pratt popular answer on the differences between Distilled water and Deionised water are good.
However, in terms of cost, production of distilled water in the laboratory is always cheaper than Deionised water. For example, A Millipore Deionised water purifier system cost you approx Rs 5-6 lakhs, while Borosil Double distillation unit (Quartz) cost anywhere between RS 15,000 - 25,000=00 based on capacity.
10th Oct, 2013
Fares Saleh
Aston University
Unit cost mean production cost per unit steam(i.e.kg) produced{fixed&variable costs}
a chem.eng. Job.
1st Nov, 2013
Reda Gadelkareem
Benha University
Is the distilled water free from THM ?
4th Nov, 2013
Indranil Das
Fertiliser Control Laboratory Midnapore Govt. of West Bengal
DI removes ionic impurities in water but it cannot remove the organic /microbial/soluble matter. Hoqwever in distilled especially double and triple the vapour forms give pure water as it is free from these substances
6th Nov, 2013
Doaa Mohamed
We must be careful to fully explain the term "distilled water" as it is possible, especially in simple distillation to transfer droplets of water (from the boiling bulk phase) along with the gaseous water phase (note visible steam contains small water droplets --- this is termed "wet steam" as opposed to "dry steam" which is not visible and does not contain water droplets). Water quality also depends on the microbiological burden (load/content). For "high quality" distilled water the distillation should be carried out in "inert" equipment and involve fractional distillation to eliminate water droplet carry-over from the boiling bulk phase ----- the pharmaceutical industry uses multi-distillation systems for generating very high quality distilled water since elimination of water droplet carry-over prevents microbial carry-over of either viable bacteria or endotoxins (released from dead bacteria).
7th Nov, 2013
Virendra Kumar Saxena
National Geophysical Research Institute
In general Distilled water pH from 6.5 to 6.8; whereas Deionized water pH from 6.8-7.1.
8th Nov, 2013
prof V.S Muralidharan
Central Electrochemical Research Institute
distilled water with purification is nonconducting and can be used in medicine
Deionised water is for washing glasswares
8th Nov, 2013
Obinna Ofoegbu
Federal University of Agriculture, Makurdi
Apart from observed electrolytic differences, DI occurs as a result of ionization potentials of materials where as distilled water operations make use of physical phase separations based on chemo-physical properties of water and matter.
10th Nov, 2013
Esam A. Elhefian
University of Zawia
As far as I am concerned, the difference between deionised water and distilled water is that deionized water is water produced by use of ion exchangers (takes away ions) while distilled water is obtained by vaporization, and then cooling the steam (condensation), which is almost free of any impurities.
1 Recommendation
13th Nov, 2013
Vladimir E Bondybey
Technische Universität München
Distillation is a process where the water is boiled and the vapor produced is then condensed, converted back to liquid water. The nonvolatile impurities are thus removed, but the distilled water may still contain volatile impurities. In the "deionization", the common ions such as Mg++, Ca++, Na+ or Cl- are removed, or more exactly exchanged for H+ and OH-, that is the deionized water still contains these ions in concentration of about 10-7. Deionization will not remove non-ionic impurities.
1 Recommendation
15th Nov, 2013
Darrell Kirk Nordstrom
U.S. Geological Survey Emeritus - Natural Hazards Mission Area
Most of the previous responses help answer the question but a little further clarification seems necessary. First, measuring pH of nearly pure water is probably best done with a technique other than using a glass electrode, such as conductivity. The reason for this is that the glass electrode measurement is fraught with several sources of error: liquid junction potentials, stirring errors, errors based on what standard buffers are used and how many are used in the calibration, etc. (see Bates, 1973 and a whole series of articles since). Second, the pH of deionized water and distilled water will depend on whether it is allowed to be open to the atmosphere or not and, if not, it should be kept flushed with pure nitrogen gas or argon. Third, it will also depend on how clean is the water from either a deionizing system or from a still. Deionizing resins can be a source of contaminants which are not always indicated by the conductance detector (boron, zinc, organics, microbes) and stills can be contaminated as well although if carefully maintained and double or triple distillation is used it is usually purer. Any aqueous solution stored in plastic will ultimately grow a microbial colony, even without detectable nutrients. Considerable research and papers were published in the 1970s and 1980s on measuring pH in low ionic strength solutions because of the work on acid rain chemistry. Papers by Metcalf and by Covington have addressed these problems and the most recent paper with good references is Kadis and Leito (2010) Anal. Chim. Acta 664, 129-134. One other very good paper not widely known or cited is Busenberg and Plummer (1987) pH measurement of low conductivity waters, USGS WRIR 87-4060, 22 pp. If anyone needs further information or papers not easily accessable, feel free to contact me.
4 Recommendations
16th Nov, 2013
Seyyed Jafar Saghanezhad
ACECR-Production Technology Research Institute, Ahvaz, Iran
Distilled water is a water that is desalinated with the aide of distillation technique
Deionized water is a water that is deionized (ions have been removed) with the aide of reverse osmosis(RO) or Ion exchange resins
you can refer to standards (ISO or ASTM) that a water should have to meet your interest
there are hundreds of standards relating to water
16th Nov, 2013
Alexander J. Babchin
Alberta Research Council (ARC)
Fellows, I measured the Real and Imaginary parts of Conductivity using HP Briges between frequences 5 Hz and 1 MHz, for both, Distilled and Deionised Water. Deionised Water had lower Real part of Conductivity by, at least, one order of magnitude at low frequency range, than Distilled Water.
3 Recommendations
16th Nov, 2013
Alexander J. Babchin
Alberta Research Council (ARC)
Sorry, Between 5 Hz and 1 GHz !
1 Recommendation
19th Nov, 2013
Amane Jada
IS2M-CNRS-UHA (Mulhouse-FRANCE)
The ionic strength of distilled water should be higher than that of the deionized water.
2 Recommendations
19th Nov, 2013
Amane Jada
IS2M-CNRS-UHA (Mulhouse-FRANCE)
The deionized water have a greater pH value than distilled water. pH of the deionized water is around 7 and the pH of distilled water is aroud 6.
3 Recommendations
19th Nov, 2013
Paul Karol
Carnegie Mellon University
Practically speaking, distilled water has been evaporated and re-condensed. It could contain other volatile substances (ethanol, e.g.) that evaporate in the same fashion, but no salts. Deionized water has salts removed, but not all impurities are salts. For example, sugar dissolved in water can be said to be deionized as can ethanol dissolved in water.
1 Recommendation
19th Nov, 2013
Alexander J. Babchin
Alberta Research Council (ARC)
Distillation by boiling leads to steam. Steam quality 80 % is considered high. But still, 20 % of mass is transported by water droplets, which have salinity of bulk linitial liquid.
1 Recommendation
19th Nov, 2013
Paul Karol
Carnegie Mellon University
My practical description of distilled water made no mention of boiling, only evaporation. You do not evaporate droplets of water.
2 Recommendations
20th Nov, 2013
Alexander J. Babchin
Alberta Research Council (ARC)
@Paul
That is true, of couse. And the lower the temperature of evaporation, the more deionised water one can get. When I compared WATERS, I run the tap water through Millipore Filter, took Distilled water from the lab. The way this water was distilled was unknown to me. But DI water had lower conductivity in samples I run.
2 Recommendations
21st Nov, 2013
Ganbat Batdemberel
Mongolian University of Science and Technology
Good question
2 Recommendations

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