[alexbold]

is it possible to use deionized water in a reaction instead of milli-q water?
how much would be the difference? is it possible to predict their differences in a reaction, if there is any?
what about it when it comes to making some solutions like dilute hydrochloric acid or sodium hydroxide?

Thanks

[chenbeier]

It is a question of purity. Some reaction need very clean water.

[Corribus]

Too vague. All depends on what you're doing.

Just FYI: "deionized" and "milli-q" don't have any official meanings, nor "nanopure". Really, there's no such thing as "deionized" water. There's always some base level of ion content. It's just a matter of how deonized it is, which is usually represented by a conductivity or resistance value. If you don't know what the resistance value is, then you don't really have any idea what the ion content is, other than a vague feeling that it's got to be less than tap water. You may have seen "Type 1" or "Type 2", "distilled", all these different things... anyway, it's better to be specific when you can, and know exactly what you have, especially if your procedure is known to be sensitive to it.