[redzilla]

Hi Everyone,

I am in the middle of preparing a standard titanium dioxide volumetric solution. The TiO2 was dissolved in concentrated H2SO4 and then was transferred appropriately to a volumetric flask. A little more H2SO4 was added and then I just needed to fill it to the mark with water, which I did. As soon as I inverted the flask to mix the solution, the volume immediately decreased by about a mL. I continued mixing and when I was done, the solution looked like it decreased in volume by a few mL's.

My question is...do I add more water to the flask to bring it back to volume, or do I leave it as is? What are the consequences in terms of the concentration if I were to leave it as is, or if I would bring it to the mark again? *delete me*!

[Borek]

Fill it up, you must know final volume, not some intermediary values. Such contraction in volume  is nothing unusual, especially if you use more concentrated solutions - volume is not additive.