What is the difference between distilled and demineralized water?

Answer 1

We've got to point out that there isn't a ton of difference - at least not in the finished product. But let's look at what differences there are.

Perhaps the obvious difference between demineralized water and distilled water is the method of purification. Demineralized water is water run through a resin bed to pull out the "junk" and deliver clean end product. Distilled water is "boiled off" and the vapor cooled to condense and recover a nearly pure product. Resin beds can range from "really good" to "super good" to increase the purity of the water, and distillation can be repeated (double distilled) to improve the finished product.

Some things are going to "sneak through" the distillation process, but not many. This is arguably the "best" way to get the purest water from the general laboratory support facility. Resin bed processing will remove ionic products, but will let though some dissolved materials which are uncharged - like many organic compounds. Living microorganisms can also get through because the resin cannot "stop" them unless it mechanically traps them. To kick the demineralizers up a notch, we can use more sophisticated (and more expensive) resins and better filtration. Consideration should be given to the use of the water and how much "contamination" can be tolerated.

Distillation leaves behind in the evaporator concentrations of all the "junk" that is being removed from the water. Buildup of scale is problem. Maintenance considerations aside, energy costs, even in a vacuum still, can be considerable for larger quantities of water. Resin costs money, too, so renewing the beds is something that must be budgeted for. The lab manager will consult with the laboratory supervisor to determine which method provides the best value for their application while maintaining quality that will not compromise the work.

Scan the Wikipedia article on purified water and visit the link at the Related Links for more information..

Answer 2

The differences are not so important.

Distilled water is obtained by distillation.

Demineralized water is obtained by purification with ion-exchangers. It is possible to remain some traces of organic compounds. But today demineralized water installations are more complex and adequate to any applications; and demineralization avoid heating.

Answer 3

Distilled water is water that has been heated into steam and then condensed back into liquid form, removing impurities and minerals. Demineralized water, on the other hand, is water that has had most or all of its mineral content removed through various processes such as reverse osmosis or deionization. Both types of water are essentially purified, but demineralized water may still contain some impurities while distilled water is typically more pure.