How long will deionized water last in an open container?

Question

I'm wanting to know about how long the water will stay deionized. It is not completely sealed air tight but it is still clean. I't been sitting for months and goes in chillers and coolant for plasma torch.

Answer 1

Do you mean: how long before it evaporates? It will dry up at essentially the same rate as regular water under the same conditions.

If you mean: how long would it stay deionized? it would depend on the amount of dust and other matter floating around in the air and how pure it needs to be for your particular experiment or process.

Added:

If the water is in plastic or glass containers, the only way for significant quantities of ions to get in the water is from contamination with inorganic materials, such as cement dust, salt, other chemical-like materials handled (or from sweeping up) in the vicinity of the water containers or metallic particles from grinding or machining operations, etc. Also, sometimes you can get microbal growth in distilled or deionized water that has been standing a long time not sealed (although they are not ions, they can cause problems for some applications).