Why is deionized water not an entirely

It sounds like you've done just the tests needed to show that these spots are from some residue. De-ionized water has usually been run through an ion-exchange resin that pulls out most anions and cations. That can still leave traces of other gunk, and I guess that's what you're seeing. Sorry I can't be more specific. Perhaps with distilled water or reverse-osmosis purified water you'd not get those residues. In the lab when we wanted de-ionized water on demand, we'd usually use columns of de-ionizing resin, available commercially.

Occasionally you have to replace the columns. Alternatives are old-fashioned stills not very convenient or energy efficient or reverse-osmosis systems.

Industrial users seem to generally prefer the exchange resins, I suppose for price reasons. You can monitor the output with a conductivity meter. Thanks for the info. I have one small quibble. That way whatever organic gunk it gave off would be removed in the second stage.

Follow-up on this answer. Learn more physics! Related Questions. Still Curious? What is dieonized water? Deionized Water We call it "DI water" in the chemistry labs is just what it sounds like: Water that has the ions removed. Water is usually deionized by using an ion exchange process. Why de-ionize water? Often, when you are doing chemistry experiments, the ions in water will be an interference.

They can switch places with other ions you may be interested in experimenting on. You may also be interested in finding out what elements are in a small sample of material. For example, a farmer may want to know what's in his soil, or the Environmental Protection Agency wants to know what a factory's emitting into the air. Dissolving the sample in water and doing tests on the result is a common technique, and contaminants in the water will make the whole test give the wrong answers.

Water with ions in it is also quite a lot more electrically conductive than water without ions in it. If you boil water with lots of ions in it until all the water's gone, you'll have a crusty salt residue in your pot.

This has critical implications, especially for the medical industry. When medical product manufacturers create a product, water is almost always mixed in. That way, when the Saline formula is added to the water, it creates an exact replica of the solution they need.

If the water contains any impurities or metal, such as copper or lead, it will cause adverse health effects for whomever injects the product.

Deionized water is a critical element for the industries that need it. Especially in the medical industry, failing to use a safe deionized water system can have serious and, as we saw with the example above, potentially fatal consequences. Get your free quote! Your email address will not be published.

Notify me of follow-up comments by email. Notify me of new posts by email. About Lenntech. General Delivery Conditions. Privacy Policy. All rights reserved. It is quite difficult to find clear definitions and standards for distilled, demineralized and deionized water. Probably the easiest way to familiarise in the topic of producing ultra pure water is to start with the oldest and best-know method: distilling.

Distilled water is water that has been boiled in an apparatus called a "still" and then recondensed in a cooling unit "condenser" to return the water to the liquid state. Distilling is used to purify water. Dissolved contaminants like salts are left behind in the boiling pot as the water vapour rises away.

It might not work if the contaminants are volatile so that they also boil and recondense, such as having some dissolved alcohol. Very elegant stills can selectively condense liquefy water from other volatile substances, but most distillation processes allow carry-over of at least some volatile substances, and a very little of the non-volatile material that was carried into the water vapour stream as bubbles burst at the surface of the boiling water.

Maximum purity from such stills is usually 1. Additionally, you have to be careful not to re-contaminate the water after distilling it. Deionization entails removal of electrically charged ionized dissolved substances by binding them to positively or negatively charged sites on a resin as the water passes through a column packed with this resin.

This process is called ion exchange and can be used in different ways to produce deionized water of various qualities. Water flows through the cation column, whereupon all the cations are exchanged for hydrogen ions. The decationised water then flows through the anion column. This time, all the negatively charged ions are exchanged for hydroxide ions which then combine with the hydrogen ions to form water H 2 O.

In the majority of cases it is advisable to reduce the flux of ions passed to the anion exchanger by installing a CO 2 removal unit between the ion exchange vessels. In general the strong acid cation and strong base anion resin system is the simplest arrangement and a deionized water that may be used in a wide variety of applications can be obtained with it. It provides the same quality of deionized water, while offering economic advantages when treating water which contains high loads of strong anions chlorides and sulphates.

The subtitle shows that the system is equipped with an extra weak base anion exchanger before the final strong base anion exchanger. The optional CO 2 removal unit may be installed either after the cation exchanger, or between the two anion exchangers see picture below. The regeneration of the anion exchangers takes place with caustic soda NaOH solution first passing through the strong base resin and then through the weak base resin.

This method requires less caustic soda than the method described before because the remaining regeneration solution after the strong base anion exchanger is usually sufficient to regenerate the weak base resin completely. Moreover, when raw water contains a high proportion of organic matter, the weak base resin protects the strong base resin. Mixed-bed Deionization In mixed-bed deionizers the cation-exchange and anion-exchange resins are intimately mixed and contained in a single pressure vessel.

The two resins are mixed by agitation with compressed air, so that the hole bed can be regard as an infinite number of anion and cation exchangers in series mixed bed resin.