aliquot
/ AL-ih-kwot /
Imagine a big pot of well-stirred soup: if you ladle out one cup, taste it, and it represents the whole pot, then that cup is a faithful sample of the whole. An aliquot is exactly that — a precisely measured portion taken from a larger, uniform solution.
An aliquot is an accurately known fraction of a sample solution, usually measured out with a pipette, that you take to work on instead of using the whole thing. Because its volume is exactly known, the result you get for the aliquot can be scaled up to describe the entire solution.
It matters because it lets one carefully prepared solution serve for several measurements — you can titrate three identical aliquots and average them, or run different tests on equal portions. The key requirement is that the parent solution be thoroughly mixed, so every aliquot truly represents the whole.
A student dissolves a tablet in a 250 mL volumetric flask, then pipettes three 25.00 mL aliquots and titrates each, averaging the results to get a precise answer for the whole tablet.
A precisely measured slice of a well-mixed whole.
An aliquot is strictly an exactly known portion — the kind you pipette — not just any random scoop. Taking several aliquots and titrating them is how analysts build replicate measurements to judge precision.