Deionized vs. distilled water

A. Though both methods will produce fairly pure H2O, I believe their difference may primarily be found in their processes. Distilled water is made by boiling impure water (most solutes get left behind), then collecting the condensation in a separate container. This process may be repeated many times before considered complete. Deionized water is usually produced by running it through a series of filters. These include but are not limited to charcoal filters and semi-permeable ion membranes. I believe deionized water can be more pure if you have some high-dollar equipment.

First of two simultaneous responses --

A. Jon's post is good, but not technically correct. Filtering water thru extremely fine filters is called ultra filtration. Filtering it thru activated carbon removes much of the chlorine and some of the organics. Water can be forced thru a membrane under pressure to get a reasonable quality of water is called RO or reverse osmosis. DI water is a water produced by an ion exchange process in a chamber (s). It removes most of the anions and cations leaving pure to extremely pure water. It must be periodically regenerated.

Second of two simultaneous responses --

A. It's all horses for courses. The main difference between DI water and distilled is that in DI water, as the name suggests, it has had its unwanted ions taken out and replaced with hydroxide and hydrogen as applicable. Distilled water has been boiled and condensed. This not only removes all the rogue ions but it also removes many of the dissolved gases, which DI water doesn't do. Saying that, leaving distilled water for any time will allow gases to redissolve and you will be back to square one. If you are doing serious analytical work, I would recommend you use distilled water, and preferably triply distilled water (i.e. distilled three times). It must also be very fresh. If you are doing routine chemistry where absolute purity is not important, use the cheaper DI water.

We have been having problems with deionised water and our Daphnia Magna; we think it has killed them. Can we have some help. Thanks.

A. What else are you giving them? Organisms need trace amounts of minerals and ions to survive (an experiment showed mice prefer to drink water with trace amounts of metal rather than pure water), so if you're just giving them deionized H2O and food, yeah, poor things may be lacking!

I use spring water for my Daphnia and they get along pretty well. Alternately you can use tap water, but be sure you let it sit for at least a day to allow chlorine gas (which would kill the daphnia) to escape. I usually just fill up a carboy on Friday and then use it monday.

Hi Jenny.

You can get a kit for learning how it's done.
or a packaged distillation unit of almost any size. Good luck.

Regards,

Q. How would you produce distilled water for routine use in the laboratory?

A. Hi Abraham. I'm trying, unsuccessfully so far, to understand how your question differs from Jenny's, which I just finished answering. If you don't understand something, please try your best to frame your question in terms of the answers already offered instead of just posting the very same question again with no clue about why you don't understand the answer. Thanks.

Regards,

A. Hi Justin. You can buy distilled or de-ionized water inexpensively by the gallon from supermarkets. It's used for a lot of things like in steam irons.

There isn't a cheap and easy way to make it at home, although you can "Call your Culligan man" or his competitors and rent a de-ionizing system if you need more than a few gallons, or buy a de-ionizer. Good luck.

Regards,