= Solution preparation and volumetric calibration
A calibration mark can be tested against an independent <mass> measurement. The Buffalo State-hosted Laboratory Experiment 1. Calibration of Volumetric Glassware uses a $25\,\mathrm{mL}$ <pipette>, filler, <conical flask>, weighing bottle, balance, and thermometer. It specifies clean, freely draining glassware, bubble-free filling, an eye-level <liquid meniscus> reading, gravity drainage, and retaining the residual liquid allowed for by the <pipette>'s calibration. Degassed <water> is delivered to a tared bottle; ten weighings and initial/final <temperature> readings give repeated delivered <volumes> using the <water> <mass density>. Their <mean> and <standard deviation> assess delivery and repeatability. The balance and thermometer must themselves be checked before claiming accuracy. The same handout describes weighing an empty <volumetric flask> and then weighing it filled to its mark.<Calibration of Volumetric Glassware (Buffalo State laboratory handout)>[Laboratory Experiment 1. Calibration of Volumetric Glassware, pp. 1–3: flask principle; Calibrating 25 mL pipette; Calibration Procedure, steps 1–8]{ref}
The independent inference is $V=m_{\mathrm{water}}/\rho_{\mathrm{water}}(T)$. Agreement between repeats constrains scatter; agreement with the nominal delivery additionally needs trustworthy <mass density>, <temperature>, and balance readings. This experiment tests delivered or contained <volume (thermodynamics)> under its conditions. It does not prove that a subsequent <solute> transfer is complete or a prepared <chemical solution> is homogeneous.
The University of Wisconsin–Madison teaching module supplies the complementary preparation demonstration. Dissolved <solute> and vessel rinsings reach the <volumetric flask>; the contents reach room <temperature> before a dropper adjusts the eye-level <liquid meniscus> to the calibration mark. The module excludes a stirring bar during filling because its displaced <volume (thermodynamics)> is absent from the calibration, and requires mixing the neck liquid with the bulk <chemical solution>. Its self-check identifies incomplete <dissolution> and transfer as a cause of lower-than-intended <molar concentration>.<Volumetric Flask: Dissolving a Solute (Wisconsin chemistry teaching module)>[Volumetric Flask: Dissolving a Solute, transfer paragraph and incomplete-dissolution self-check]{ref}<Volumetric Flask: Filling a Volumetric Flask (Wisconsin chemistry teaching module)>[Volumetric Flask: Filling a Volumetric Flask, temperature, displaced volume, and eye-level mark reading]{ref}<Volumetric Flask: Mixing the Solution in a Volumetric Flask (Wisconsin chemistry teaching module)>[Volumetric Flask: Mixing the Solution in a Volumetric Flask, neck/bulk concentration difference]{ref}
The observable endpoints are a liquid boundary at a mark and a delivered <mass>, not a direct count of <solute> particles. An overfilled flask has excessive final <volume (thermodynamics)>; removing some well-mixed <chemical solution> also removes <solute>, so it cannot recover the intended inventory merely by restoring the mark. <Measurement uncertainty>, contamination, incomplete transfer, and sampling before full mixing limit the inferred <molar concentration>. The apparatus demonstrates why the words “dilute to” refer to final <chemical solution> <volume (thermodynamics)>.
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