[connormcdowell]

The salt spray cabinet I am using requires approx 60L of saline solution (5% sodium chloride, 95% distilled water). The standard I'm working to requires that the test engineer measures the pH of the solution before and after the test.

The standard also states that distilled water absorbs carbon from the air which reduces its pH, but only temporarily. It is suggested that the pH will return to its previous value when atomised and combined with pressurised humid air during test.

Through some reading around I've learnt that pure sodium chloride shouldn't affect the pH of distilled water in itself. My question is this: If I measure of the pH of the distilled water as soon as I open the bottle, will this be an accurate representation of the solution's pH inside the chamber?

Alternatively, is there a magic equation (for a chemistry layman) relating the absorption of carbon dioxide into distilled water over time and ph value?

Thanks.

[Borek]

Measuring pH of distilled water can be a tricky business, as its resistance is quite high.