pH of demin water

[DocMax]

Hello
Let me know a confirm concerning demin water, the pH of demin water after the DW process (SAC and SBA) is pH =7.
I know the pH misure for DW is not a verry good and it's better the Conductivity determination. But the pH will be drop for a CO2 dissolution and produce H2CO3? Is this correct right? How will be the pH drop?

Thanks

 

[bimr]

You are incorrect. The pH of demineralized water is basic due to OH ion.

The leakage from a cation unit is sodium. The leakage from an anion unit is OH. So you get a basic pH of 8-10 units from the NaOH in the demineralizer effluent.

Of course, having said that, the water is so slightly buffered that it the pH can change very easily.

If the water is allowed in contact with the atmosphere, then CO2 will be absorbed from the air into the water. The pH may then drop down to 5-6 pH units.