For an acid-base titration, a volumetric pipette selects an aliquot whose amount of substance is from a homogeneous sample. The delivered volume depends on the instrument's calibration and drainage convention; the residual liquid of a gravity-draining volumetric pipette is allowed for in that calibration. Its mark is read using the liquid meniscus. A volume calibration alone does not establish that the sampled chemical solution has the intended concentration.[ref]
Calibration of Volumetric Glassware (Buffalo State laboratory handout). Laboratory Experiment 1. Calibration of Volumetric Glassware, pp. 1–2, Calibrating 25 mL pipette: eye-level meniscus, gravity drainage, retained liquid
An aliquot is a measured portion taken from a larger sample. For a homogeneous chemical solution, it contains the corresponding fraction of each conserved component inventory. Representative sampling requires mixing; knowing only the portion's volume is insufficient if the sample is not homogeneous.
A volumetric pipette transfers one nominal volume of chemical solution according to its marked calibration and drainage convention.
