Adding base to an acid in titrations

[elseany]

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Why do we always add a base to an acid when doing titrations? im fairly sure my teacher mentioned this and he explained it, i just cant for the life of me remember what he said. i asked a class mate and he's telling me that its because the glass flask is made of silicon oxide which is acidic, if we put the abse in the flask it will react with the glass but i find this hard to beleive, can anyone clarify please?

[Aerlinn]

Isn't it supposed to be that we 'usually' add an acid to the base? There are exceptions, but...

[idling fire]

In my class, we almost always add acid to base...

I cannot see a particular "law" for either method. Though if you have NaOH in your burette and you leave it overnight (yes, I'm slow at titration and didn't finish it so left the equipment out) it tends to react with air at the top, form a sediment on the bottom, and completely ruin your experiment.
-> from experience.

Though it might depend on what indicator you use. Phenolphthalein? I find it easier to observe the colour change from clear to pink (ie. adding base to acid) than the reverse. That could be a reason...