[jkrueger0408]

http://www.chemicalforums.com/index.php?topic=35881.0

Thing is I totally understand this, and agree, but when i measure the pH of a 0.45M solution, my pH meter reads 10.20

As well, when added to DI water it increases the pH

Should I suspect a problem with my pH meter or sample contamination?

If it is a pH meter artifact, what could be causing that reading?

This is driving me nuts!

[jkrueger0408]

Or how about this: bicarbonate contamination in the DI water and CO2 dissolving in the water creates Ca(HCO3)2??

[Borek]

Or how about this: bicarbonate contamination in the DI water and CO2 dissolving in the water creates Ca(HCO3)2??

Presence of CO₂ can only lower pH, never increase it.

[jkrueger0408]

Is there some other explaination? Impurity in the CaCl2?

[jkrueger0408]

Or how about this: bicarbonate contamination in the DI water and CO2 dissolving in the water creates Ca(HCO3)2??

Presence of CO₂ can only lower pH, never increase it.

Maybe impurity from the Solvay process?

2 NaCl + CaCO3 → Na2CO3 + CaCl2

could make it slightly basic...

Sorry if I am being rude, but I would really like to understand how the salt could be alkaline!

[Borek]

Maybe impurity from the Solvay process?

That was already suggested earlier in the thread. Can't say I have new ideas.