Volumetric flask
= Volumetric flask
A <volumetric flask> prepares a <chemical solution> at a specified total <volume (thermodynamics)>, using a calibration mark.
Its mark specifies contained <volume (thermodynamics)> under its calibration conditions. In contrast, a <volumetric pipette> specifies a delivered portion. The narrow neck makes a small change of <volume (thermodynamics)> visible as a larger change of liquid height. The final <chemical solution> <volume (thermodynamics)> includes the <solute>; “dilute to $100\,\mathrm{mL}$” does not mean “add $100\,\mathrm{mL}$ of <water>”.<Calibration of Volumetric Glassware (Buffalo State laboratory handout)>[Laboratory Experiment 1. Calibration of Volumetric Glassware, p. 1, distinction between contained and delivered volumes and flask calibration principle]{ref}
For an original <dilution> example, a fully transferred $10.00\,\mathrm{mL}$ <aliquot> of $0.100\,\mathrm{mol\,L^{-1}}$ acid contains $1.000\,\mathrm{mmol}$. Making the final total $100.0\,\mathrm{mL}$ gives <analytical concentration> $0.0100\,\mathrm{mol\,L^{-1}}$. A subsequent $10.00\,\mathrm{mL}$ <aliquot> contains $0.1000\,\mathrm{mmol}$ and needs $1.000\,\mathrm{mL}$ of $0.100\,\mathrm{mol\,L^{-1}}$ base for one-to-one <neutralization>. The entire diluted flask still needs $10.00\,\mathrm{mL}$ of that base: <dilution> preserves the selected inventory but sampling selects a fraction of it.
Overfilling lowers the intended <molar concentration>. Removing some well-mixed <chemical solution> to restore the mark also removes <solute>, so it does not recover the intended inventory. Full transfer, known final <volume (thermodynamics)>, and mixing are separate requirements.